CISCO Nexus 9000 Configuring Static and DynamicNAT Translation

Product Information

Specifications

• Product: Cisco Nexus device
• NAT Type: Static and Dynamic NAT Translation
• Supports Hitless NAT
• Supports Port Address Translation (PAT)
• Supports access control lists (ACLs)
• Timeout configurations: 60 seconds to 172800 seconds

Product Usage Instructions

Configuring Static NAT Translation
Static Network Address Translation (NAT) allows the user to configure one- to-one translations of the inside local addresses to the outside global addresses. It supports both IP addresses and port number translations from the inside to the outside traffic and vice versa.

To configure static NAT translation:

1. Ensure you have an equal number of public addresses as private addresses.
2. Create a fixed translation of private addresses to public addresses.
3. If an access list exists, allow traffic initiation from hosts on the destination network to a translated host.
4. To add or remove a NAT translation, use the Hitless NAT feature, which does not affect existing NAT traffic flows.

Configuring Dynamic NAT Translation
Dynamic NAT allows each host to use a different address or port for each subsequent translation. It supports Port Address Translation (PAT) and access control lists (ACLs).

To configure dynamic NAT translation:

1. Ensure your NAT configuration can have multiple dynamic NAT translations with the same or different ACLs.
2. For a given ACL, specify only one interface.
3. Configure timeouts for dynamic entries. Default timeout is one hour (60 minutes), but you can configure it from 60 to 172800 seconds.

NAT Inside and Outside Addresses

When configuring NAT, you need to define inside and outside addresses.

To define NAT inside and outside addresses:

1. Identify the network interfaces as inside or outside.
2. Specify the inside and outside addresses accordingly.

Pool Support for Dynamic NAT
The Cisco Nexus device supports pool-based dynamic NAT.

Frequently Asked Questions (FAQ)

Q: What is Static NAT?
A: Static NAT allows for one-to-one translations of inside local addresses to outside global addresses, enabling fixed translations of private addresses to public addresses.

Q: What is Dynamic NAT?
A: Dynamic NAT allows each host to use a different address or port for each subsequent translation. It supports Port Address Translation (PAT) and access control lists (ACLs).

Q: What is Hitless NAT?
A: Hitless NAT is a feature supported by the Cisco Nexus device that allows you to add or remove a NAT translation in the NAT configuration without affecting existing NAT traffic flows.

Network Address Translation Overview
Network Address Translation (NAT) enables private IP internetworks that use nonregistered IP addresses to connect to the Internet. NAT operates on a device, usually connecting two networks, and translates private (not globally unique) IP addresses in the internal network into legal IP addresses before packets are forwarded to another network. You can configure NAT to advertise only one IP address for the entire network to the outside world. This ability provides additional security, effectively hiding the entire internal network behind one IP address.
A device configured with NAT has at least one interface to the inside network and one to the outside network. In a typical environment, NAT is configured at the exit router between a stub domain and a backbone. When a packet leaves the domain, NAT translates the locally significant source IP address into a globally unique IP address. When a packet enters the domain, NAT translates the globally unique destination IP address into a local IP address. If more than one exit point exists, NAT configured at each point must have the same translation table. NAT is described in RFC 1631.

Information About Static NAT
Static Network Address Translation (NAT) allows the user to configure one-to- one translations of the inside local addresses to the outside global addresses. It allows both IP addresses and port number translations from the inside to the outside traffic and the outside to the inside traffic. The Cisco Nexus device supports Hitless NAT, which means that you can add or remove a NAT translation in the NAT configuration without affecting the existing NAT traffic flows.
Static NAT creates a fixed translation of private addresses to public addresses. Because static NAT assigns addresses on a one-to-one basis, you need an equal number of public addresses as private addresses. Because the public address is the same for each consecutive connection with static NAT, and a persistent translation rule exists, static NAT enables hosts on the destination network to initiate traffic to a translated host if an access list exists that allows it .
With dynamic NAT and Port Address Translation (PAT), each host uses a different address or port for each subsequent translation. The main difference between dynamic NAT and static NAT is that static NAT allows a remote host to initiate a connection to a translated host if an access list exists that allows it, while dynamic NAT does not. The figure shows a typical static NAT scenario. The translation is always active so both translated and remote hosts can originate connections, and the mapped address is statically assigned by the static command.

Figure 1: Static NAT

These are key terms to help you understand static NAT:

• NAT inside interface—The Layer 3 interface that faces the private network.
• NAT outside interface—The Layer 3 interface that faces the public network.
• Local address—Any address that appears on the inside (private) portion of the network.
• Global address—Any address that appears on the outside (public) portion of the network.
• Legitimate IP address—An address that is assigned by the Network Information Center (NIC) or service provider.
• Inside local address—The IP address assigned to a host on the inside network. This address does not need to be a legitimate IP address.
• Outside local address—The IP address of an outside host as it appears to the inside network. It does not have to be a legitimate address, because it is allocated from an address space that can be routed on the inside network.
• Inside global address—A legitimate IP address that represents one or more inside local IP addresses to the outside world.
• Outside global address—The IP address that the host owner assigns to a host on the outside network. The address is a legitimate address that is allocated from an address or network space that can be routed.

Dynamic NAT Overview

Dynamic Network Address Translation (NAT) translates a group of real IP addresses into mapped IP addresses that are routable on a destination network. Dynamic NAT establishes a one-to-one mapping between unregistered and registered IP addresses; however, the mapping can vary depending on the registered IP
address that is available at the time of communication. A dynamic NAT configuration automatically creates a firewall between your internal network and outside networks or the Internet. Dynamic NAT allows only connections that originate inside the stub domain—a device on an external network cannot connect to devices in your network, unless your device has initiated the contact.
Dynamic NAT translations do not exist in the NAT translation table until a device receives traffic that requires translation. Dynamic translations are cleared or timed out when not in use to make space for new entries. Usually, NAT translation entries are cleared when the ternary content addressable memory (TCAM) entries
are limited. The default minimum timeout for dynamic NAT translations is 30 minutes.
The input translation sampling-timeout command is not supported. Statistics are collected every 60 seconds for the installed NAT policies. These statistics are used to determine if the flow is active or not.

Note
Dynamic NAT supports Port Address Translation (PAT) and access control lists (ACLs). PAT, also known as overloading, is a form of dynamic NAT that maps multiple unregistered IP addresses to a single registered IP address by using different ports. Your NAT configuration can have multiple dynamic NAT translations with same or different ACLs. However, for a given ACL, only one interface can be specified.

Timeout Mechanisms
The following NAT translation timeout timers are supported on the switch:

• timeout—Timeout value for dynamic NAT translations.

The timeout value ranges from 60 seconds to 172800 seconds, including the sampling-timeout.
The udp-timeout and the timeout value timers are triggered after the timeout configured for the ip nat translation sampling-timeout command expires.

Note There are three different options that can be configured for aging:

• Time-out: This is applicable for all type of flows(both TCP and UDP).
• TCP TIME-OUT: This is applicable for only TCP flows.
• UDP TIME-OUT: This is applicable for only UDP flows.

When you create dynamic entries without timeouts configured, they take the default timeout of one hour (60 minutes). If you enter the clear ip nat translations all command after configuring timeouts, the configured timeout take effect. A timeout can be configured from 60 to 172800 seconds.

NAT Inside and Outside Addresses

NAT inside refers to networks owned by an organization that must be translated. When NAT is configured, hosts within this network will have addresses in one space (known as the local address space) that will appear to those outside the network as being in another space (known as the global address space). Similarly, NAT outside refers to those networks to which the stub network connects. They are not generally under the control of the organization. Hosts in outside networks can be subject to translation and can have local and global addresses.

NAT uses the following definitions:

• Local address—A local IP address that appears on the inside of a network.
• Global address—A global IP address that appears on the outside of a network.
• Inside local address—The IP address that is assigned to a host on the inside network. The address is probably not a legitimate IP address assigned by the Internet Network Information Center (InterNIC) or a service provider.
• Inside global address—A legitimate IPaddress(assigned by InterNIC or a service provider) that represents one or more inside local IP addresses to the outside world.
• Outside local address—The IPaddress of an outside host as it appears to the inside network. The address is not necessarily legitimate; it was allocated from the address space that is routable on the inside.
•  Outside global address—The IP address that is assigned to a host on the outside network by the owner
  of the host. The address was allocated from a globally routable address or a network space.

Pool Support for Dynamic NAT
Cisco NX-OS provides pool support for dynamic NAT. Dynamic NAT allows the configuration of a pool of global addresses that can be used to dynamically allocate a global address from the pool for every new translation. The addresses are returned to the pool after the session ages out or is closed. This allows for a more efficient use of addresses based on requirements.

Support for PAT includes the use of the global address pool. This further optimizes IP address utilization. PAT exhausts one IPaddress at a time with the use of port numbers. If no port is available from the appropriate group and more than one IP address is configured, PAT moves to the next IP address and gets the allocation based on the user defined pool (ignoring the source port or attempting to preserve it). With dynamic NAT and PAT, each host uses a different address or port for each subsequent translation. The main difference between dynamic NAT and static NAT is that static NAT allows a remote host to initiate a connection to a translated host if an access list exists that allows it, while dynamic NAT does not. When dynamic NAT is configured to use a pool of IP addresses, that are not locally available or configured locally, the out-to-in traffic is considered as DEST MISS. Due to this behavior, the show system internal access-list dest-miss stats command output displays increment in DEST MISS counters. The DEST MISS statistics is supported from Cisco NX-OS Release 9.3(5) onwards. Beginning with Cisco NX-OS Release 10.1(1) DEST MISS statistics is supported on Cisco Nexus 9300-FX3 platform switches

Static and Dynamic Twice NAT Overview

When both the source IP address and the destination IP address are translated as a single packet that goes through a Network Address Translation (NAT) device, it is referred to as twice NAT. Twice NAT is supported for static and dynamic translations. Twice NAT allows you to configure two NAT translations (one inside and one outside) as part of a group of translations. These translations can be applied to a single packet as it flows through a NAT device. When you add two translations as part of a group, both the individual translations and the combined translation take effect. A NAT inside translation modifies the source IP address and port number when a packet flows from inside to outside. It modifies the destination IP address and port number when the packet returns from outside to inside. NAT outside translation modifies the source IP address and port number when the packet flows from outside to inside, and it modifies the destination IP address and port number when the packet returns from inside to outside. Without twice NAT, only one of the translation rules is applied on a packet, either the source IP address and port number or the destination IP address and port number. Static NAT translations that belong to the same group are considered for twice NAT configuration. If a static configuration does not have a configured group ID, the twice NAT configuration will not work. All inside and outside NAT translations that belong to a single group that is identified by the group ID are paired to form twice NAT translations. Dynamic twice NAT translations dynamically select the source IP address and port number information from pre- defined ip nat pool or interface overload configurations. Packet filtration is done by configuring ACLs, and traffic must originate from the dynamic NAT translation rule direction such that source translation is done by using dynamic NAT rules. Dynamic twice NAT allows you to configure two NAT translations (one inside and one outside) as part of a group of translations. One translation must be dynamic and other translation must be static. When these two translations are part of a group of translations, both the translations can be applied on a single packet as it goes through the NAT device either from inside to outside or from outside to inside.

VRF Aware NAT

The VRF aware NAT feature enables a switch to understand an address space in a VRF (virtual routing and forwarding instances) and to translate the packet. This allows the NAT feature to translate traffic in an overlapping address space that is used between two VRFs.

Notes for VRF aware NAT:

• The VRF aware NAT feature is supported on N9K-9408PC-CFP2, N9K-X9564PX, N9K-C9272Q, N9K-C9272Q, N9K-X9464TX, N9K-X9464TX2, N9K-X9564TX, N9K-X9464PX, N9K-X9536PQ, N9K-X9636PQ, N9K-X9432PQ, N9K-C9332PQ, N9K-C9372PX, N9K-C9372PX-E, N9K-C9372TX, N9K-C9372TX-E, N9K-C93120TX.
• The VRF aware NAT feature is not supported on the Cisco Nexus 9300-EX, 9300-FX, 9300-FX2 and 9300-GX platform switches.

Note This is a NAT TCAM limitation for the Cisco Nexus 9300-EX and 9300-FX platform switches. NAT TCAM is not VRF aware. NAT does not work with overlapping IP addresses on Cisco Nexus 9300-EX, 9300-FX, 9300-FX2 and 9300-GX platform switches.

• Beginning with Cisco NX-OS Release 10.2(3)F, VRFaware NAT issupported on Cisco Nexus 9300-FX, FX2, GX and GX2 platform switches. It is not supported on Cisco Nexus 9346C switch.

• Traffic flowing from one non-default-vrf to another non-default-vrf is not translated. (For example, vrfA to vrfB.)

• For traffic flowing from a VRF to a global-VRF, a nat-outside configuration is not supported on a non-default VRF interface.

• VRF aware NAT is supported by static and dynamic NAT configurations.

• When traffic is configured to flow from a non-default VRF (inside) to a default VRF (outside), the
  match-in-vrf option of the ip nat command cannot be specified.

• When traffic is configured to flow from a non-default VRF (inside) to the same non-default VRF (outside), the match-in-vrf option of the ip nat command must be specified.

The following is an example configuration:

Switch(config)# ip nat inside source {list } {pool [vrf [match-in-vrf]] [overload] | interface [vrf [match-in-vrf]] overload} [group dynamic] Switch(config)#ip nat outside source list pool [vrf [match-in-vrf]] [group dynamic]}

• VRF aware NAT does not support fragmented packets.

• VRF aware NAT does not support application layer translations.

• Therefore, Layer 4 and other embedded IPs are not translated and the following will fail:

  • FTP
  • ICMP failures
  • IPSec
  • HTTPS

• VRF aware NAT supports NAT or VACL on an interface. (However, both features cannot be supported at the same time on an interface.)

• VRF aware NAT supports egress ACLs that are applied to the original packet, not on the NAT translated packet.

• VRF aware NAT supports only the default VRF.

• VRF aware NAT does not provide MIB support.

• VRF aware NAT does not provide DCNM support.

• VRF aware NAT supports only a single global VDC.

• VRF aware NAT does not support the active/standby supervisor model.

• VRFs with overlapping subnets cannot go to a common destination without NAT. However, you can achieve this functionality with inter-VRF NAT on dynamic NAT rule configuration. Static NATc onfiguration is not supported for overlapping address.

Guidelines and Limitations for Static NAT
Static NAT has the following configuration guidelines and limitations:

• For Broadcom-based Cisco Nexus 9000 Series switches, if the route to your inside global address on the translating device is reachable via the outside interface, packets for Network Address Translated flows coming from outside to inside get software forwarded, duplicated, and looped in the network. For this situation, you must enter the add-route CLI argument on the end of the NAT configuration for this flow. For example, ip nat inside source static 192.168.1.1 172.16.1.1 add-route.
• The static NAT feature over vPC is supported on Cisco Nexus 9300 platform switches.
• show commands with the internal keyword are not supported.
• The static NAT feature is supported on Cisco Nexus 9300 platform switches.
• The static NAT feature is supported on Cisco Nexus 9200 platform switches.
• On Cisco Nexus 9200 and 9300-EX, -FX, -FX2, -FX3, -FXP, -GX platform switches, the add-route option is required for both inside and outside policies.

Note NAT is not supported on Cisco Nexus 9500 platform switches.

• NAT supports up to 1024 translations which include both static and dynamic NAT.
• If the translated IP is part of the outside interface subnet, then use the ip proxy-arp command on the NAT outside interface. If the add-route keyword is used, ip proxy-arp should be enabled.
• NAT and sFlow are not supported on the same port.
• Beginning with Cisco NX-OS Release 10.2(1)F, VXLAN NAT and Distributed Elastic NAT feature is supported on Cisco Nexus 9300-FX2 platform series switches. The Distributed Elastic NAT feature enables NAT on the leaf and spine in the VXLAN topology
• VXLAN NAT and Distributed Elastic NAT supports the following:
  • Upto 8000 NAT translations
  • VRF
  • Add-route for static inside configuration
  • SVI without IP address configuration
• VXLAN and Distributed Elastic NAT does not support the following:
  • IPv6
  • NAT is unaware of vPC. All the configurations should be applied on both the vPC peers.
  • The Cisco Nexus device supports NAT on the following interface types:
• Switch Virtual Interfaces (SVIs)
  • Routed ports
  • Layer 3 and Layer 3 subinterfaces.
  • NAT is supported on the default Virtual Routing and Forwarding (VRF) table only.
  • NAT is supported for IPv4 Unicast only.
• The Cisco Nexus device does not support the following:
  • Software translation. All translations are done in the hardware.
  • Application layer translation. Layer 4 and other embedded IPs are not translated, including FTP, ICMP failures, IPSec, and HTTPs.
  • NAT and VLAN Access Control Lists (VACLs) that are configured on an interface at the same time.
  • PAT translation of fragmented IP packets.
  • NAT translation on software forwarded packets. For example, packets with IP-options are not NAT translated.
• By default no TCAM entries are allocated for the NAT feature. You allocate the TCAM size for the NAT feature by adjusting the TCAM size of other features. The TCAM can be allocated with the hardware access-list tcam region nat tcam-size command.
• HSRP and VRRP are not supported on a NAT interface.
• If an IP address is used for Static NAT or PAT translations, it cannot be used for any other purpose. For example, it cannot be assigned to an interface.
• For Static NAT, the outside global IP address should be different from the outside interface IP address.
• When configuring a large number of translations (more than 100), it is faster to configure the translations before configuring the NAT interfaces.
• NAT supports (non-disruptive) In Service Software Upgrade (ISSU).
• UDF-based features may not work when NAT TCAM is carved.
• ECMP NAT is not supported on Cisco Nexus 9000 switches.
• NAT configurations such as ip nat inside or ip nat outside are not supported on loopback interfaces

Restrictions for Dynamic NAT

The following restrictions apply to dynamic Network Address Translation (NAT):

• For Broadcom-based Cisco Nexus 9000 Series switches, if the route to your inside global address on the translating device is reachable via the outside interface, packets for Network Address Translated flows coming from outside to inside get software forwarded, duplicated, and looped in the network. For this situation, you must enter the add-route CLI argument on the end of the NAT configuration for this flow.
  For example, ip nat inside source static 192.168.1.1 172.16.1.1 add-route.

• VRF aware NAT is not supported for overlapping inside/outside IP subnet addresses on Cisco Nexus 9200 and 9300-EX platform switches.

• show commands with the internal keyword are not supported.

• The dynamic NAT feature is supported on Cisco Nexus 9300 platform switches.

• The dynamic NAT feature is supported on Cisco Nexus 9200 platform switches.

• On Cisco Nexus 9200 and 9300-EX, -FX, -FX2, -FX3, -FXP, -GX platform switches, the add-route option is required for both inside and outside policies.

• The interface overload option for inside policies option is not supported on the on the Cisco Nexus 9200, 9300-EX, 9300-FX 9300-FX2, 9300-FX3, 9300-FXP, and 9300-GX platform switches for both outside and inside policies.

• VXLAN routing is not supported on Cisco Nexus devices.

• Fragmented packets are not supported.

• Application layer gateway (ALG) translations are not supported. ALG, also known as application-level gateway, is an application that translates IP address information inside the payload of an application packet.

• Egress ACLs are not applied to translated packets.

• Nondefault virtual routing and forwarding (VRF) instances are not supported.

• MIBs are not supported.

• Cisco Data Center Network Manager (DCNM) is not supported.

• Multiple global virtual device contexts (VDCs) are not supported on Cisco Nexus devices.

• Dynamic NAT translations are not synchronized with active and standby devices.

• Stateful NAT is not supported. However, NAT and Hot Standby Router Protocol (HSRP) can coexist.

• The timeout value for take up to the configured time-out + 119 seconds.

• Normally, ICMP NAT flows time out after the expiration of the configured sampling-timeout and translation-timeout. However, when ICMP NAT flows present in the switch become idle, they time out immediately after the expiration of the sampling-timeout configured.

• Hardware programming is introduced for ICMP on Cisco Nexus 9300 platform switches. Therefore, the ICMP entries consume the TCAM resources in the hardware. Because ICMP is in the hardware, the maximum limit for NAT translation in Cisco Nexus platform Seriesswitchesis changed to 1024. Maximum of 100 ICMP entries are allowed to make the best usage of the resources.

• When creating a new translation on a Cisco Nexus 9000 Series switch, the flow is software forwarded until the translation is programmed in the hardware, which might take a few seconds. During this period, there is no translation entry for the inside global address. Therefore, returning traffic is dropped. To overcome this limitation, create a loopback interface and give it an IP address that belongs to the NAT pool.

• For dynamic NAT, pool overload and interface overload are not supported for the outside NAT.

• Because the NAT overload usesPBR (Policy-Based Routing), the maximum number of available next-hop entries in the PBR table determines NAT scale. If the number of NAT inside interfaces are within the range of available next-hops entries in thePBR table, the maximum NAT translation scale remains same. Otherwise, the maximum number of supported translations may reduce. PBR and NAT-overload are not mutually exclusive; they are mutually limiting.

• The Cisco Nexus devices does not support NAT and VLAN Access Control Lists (VACLs) that are configured on an interface at the same time.

• NAT configurations such as ip nat inside or ip nat outside are not supported on loopback interfaces.

• The dynamic NAT feature over vPC is not supported.

Guidelines and Limitations for Dynamic Twice NAT

For Broadcom-based Cisco Nexus 9000 Series switches, if the route to your inside global address on the translating device is reachable via the outside interface, packets for Network Address Translated flows coming from outside to inside get software forwarded, duplicated, and looped in the network. For this situation, you must enter the add-route CLI argument on the end of the NAT configuration for this flow. For example, ip nat inside source static 192.168.1.1 172.16.1.1 add-route. IP packets without TCP/UDP/ICMP headers are not translated with dynamic NAT. In dynamic twice NAT, if dynamic NAT flows are not created before creating static NAT flows, dynamic twice NAT flows are not created correctly. When an empty ACL is created, the default rule of permit ip any any is configured. The NAT-ACL does not match further ACL entries if the first ACL is blank.

Guidelines and Limitations for TCP Aware NAT

TCP aware NAT has the following limitations:

• TCP aware NAT is supported on Cisco Nexus 9500 and Cisco Nexus 9300-EX, FX, and FX2 series switches.
• Beginning with Cisco NX-OS Release 9.3(5), TCP aware NAT is supported on Cisco Nexus N9K-C9316D-GX, N9K-C93600CD-GX, N9K-C9364C-GX switches.
• Only one match ACL can be associated with one range of addresses pool. After associating a pool to a match ACL you cannot change the interface IP or modify the pool range.
• You must define the pool before configuring or using it in a dynamic NAT configuration.
• The dynamic NAT rule must be reconfigured whenever there is a change in pool range or interface address in case of interface overload.

Configuring Static NAT

Enabling Static NAT

SUMMARY STEPS

1. switch# configure terminal
2. switch(config)# feature nat
3. switch(config)# copy running-config startup-config

DETAILED STEPS

mode.
Step 2| switch(config)# feature nat| Enables the static NAT feature on the device.
Step 3| switch(config)# copy running-config startup-config| Saves the change persistently through reboots and restarts by copying the running configuration to the startup

configuration.

Configuring Static NAT on an Interface

SUMMARY STEPS

1. switch# configure terminal
2. switch(config)# interface type slot/port
3. switch(config-if)# ip nat {inside | outside}
4. (Optional) switch(config)# copy running-config startup-config

DETAILED STEPS

mode.
Step 2| switch(config)# interface type slot / port| Specifies an interface to configure, and enters interface configuration mode.
Step 3| switch(config-if)# ip nat { inside | outside }| Specifies the interface as inside or outside.

Note **** Only packets that arrive on a marked interface can be translated.

This configuration is not supported on loopback interface.

Step 4| (Optional) switch(config)# copy running-config startup- config| Saves the change persistently through reboots and restarts by copying the running configuration to the startup

configuration.

Example
This example shows how to configure an interface with static NAT from the inside:
switch# configure terminal
switch(config)# interface ethernet 1/4
switch(config-if)# ip nat inside

Enabling Static NAT for an Inside Source Address

For inside source translation, the traffic flows from inside interface to the outside interface. NAT translates the inside local IP address to the inside global IP address. On the return traffic, the destination inside global IP address gets translated back to the inside local IP address.

Note When the Cisco Nexus device is configured to translate an inside source IP address (Src:ip1) to an outside source IPaddress(newSrc:ip2), the Cisco Nexus device implicitly adds a translation for an outside destination IP address (Dst: ip2) to an inside destination IP address (newDst: ip1).

SUMMARY STEPS

1. switch# configure terminal
2. switch(config)# ip nat inside source static local-ip-address global-ip-address [vrf vrf-name] [match-in-vrf] [group group-id ]
3. (Optional) switch(config)# copy running-config startup-config

DETAILED STEPS

mode.
Step 2| switch(config)# ip nat inside source static local-ip- address global-ip-address [ vrf vrf-name ] [ match-in-vrf ] [ group group-id ]| Configures static NAT to translate the inside local address to the inside global address or to translate the opposite (the inside global traffic to the inside local traffic). Specifying group specifies the group to which this translation belongs on the static twice NAT.

Note **** While performing twice NAT configuration in Cisco Nexus 9000 Series switches, you

cannot use the same group ID across different VRFs. A unique group ID should be used for unique twice NAT rules.

Step 3| (Optional) switch(config)# copy running-config startup- config| Saves the change persistently through reboots and restarts by copying the running configuration to the startup

configuration.

Example
This example shows how to configure static NAT for an inside source address:

• switch# configure terminal
• switch(config)# ip nat inside source static 1.1.1.1 5.5.5.5
• switch(config)# copy running-config startup-config

Enabling Static NAT for an Outside Source Address
For outside source translation, the traffic flowsfrom the outside interface to the inside interface. NAT translates the outside global IP address to the outside local IP address. On the return traffic, the destination outside local IP address gets translated back to outside global IP address.

SUMMARY STEPS

1. switch# configure terminal
2. switch(config)# ipnat outside source static outsideGlobalIP outsideLocalIP [vrf vrf-name [match-in-vrf] [group group-id] [dynamic] [add-route] ]
3. (Optional) switch(config)# copy running-config startup-config

DETAILED STEP

mode.
Step 2| switch(config)# ip nat outside source static

outsideGlobalIP outsideLocalIP [ vrf vrf-name

| Configures static NAT to translate the outside global address to the outside local address or to translate the opposite (the outside local traffic to the outside global traffic). Specifying
 | Command or Action| Purpose
---|---|---
 | [ match-in-vrf ] [ group group-id ] [ dynamic ] [ add- route ]

]

| group specifies the group to which this translation belongs

on the static twice NAT. When an inside translation without ports is configured, an implicit add route is performed. The original add route functionality is an option while

configuring an outside translation.

Step 3| (Optional) switch(config)# copy running-config startup- config| Saves the change persistently through reboots and restarts by copying the running configuration to the startup

configuration.

Example
This example show how to configure static NAT for an outside source address:

• switch# configure terminal
• switch(config)# ip nat outside source static 2.2.2.2 6.6.6.6
• switch(config)# copy running-config startup-config

Configuring Static PAT for an Inside Source Address

You can map services to specific inside hosts using Port Address Translation (PAT).

SUMMARY STEPS

1. switch# configure terminal
2. switch(config)# ip nat inside source static {inside-local-address inside-global-address | {tcp| udp} inside-local-address {local-tcp-port | local-udp-port} inside-global-address {global-tcp-port |global-udp-port}} {vrf vrf-name {match-in-vrf} {group group-id} }
3. (Optional) switch(config)# copy running-config startup-config

DETAILED STEPS

mode.
Step 2| switch(config)# ip nat inside source static

{ inside-local-address inside-global-address | { tcp | udp } inside-local-address { local-tcp-port | local-udp-port } inside-global- address { global-tcp-port | global-udp-port }}

{ vrf vrf-name { match-in-vrf } { group group-id } }

| Maps static NAT to an inside local port to an inside global port.
Step 3| (Optional) switch(config)# copy running-config startup- config| Saves the change persistently through reboots and restarts by copying the running configuration to the startup

configuration.

Example
This example shows how to map UDP services to a specific inside source address and UDP port:

• switch# configure terminal
• switch(config)# ip nat inside source static udp 20.1.9.2 63 35.48.35.48 130
• switch(config)# copy running-config startup-config

Configuring Static PAT for an Outside Source Address
You can map services to specific outside hosts using Port Address Translation (PAT).

SUMMARY STEPS

1. switch# configure terminal
2. switch(config)# ip nat outside source static {outside-global-address outside-local-address | {tcp | udp} outside-global-address {global-tcp-port | global-udp-port} outside-local-address {global-tcp-port |global-udp-port}} {group group-id} {add-route} {vrf vrf-name {match-in-vrf}}
3. (Optional) switch(config)# copy running-config startup-config

DETAILED STEPS

mode.
Step 2| switch(config)# ip nat outside source static

{ outside-global-address outside-local-address | { tcp | udp } outside-global-address { global-tcp-port | global-udp-port } outside- local-address { global-tcp-port | global-udp-port }}

{ group group-id } { add-route } { vrf vrf-name

{ match-in- vrf }}

| Maps static NAT to an outside global port to an outside local port.

Specifying group specifies the group to which this translation belongs on the static twice NAT. When an inside translation without ports is configured, an implicit add route is performed. The original add route functionality is an option while configuration an outside translation.

Step 3| (Optional) switch(config)# copy running-config startup- config| Saves the change persistently through reboots and restarts by copying the running configuration to the startup

configuration.

Example
This example shows how to map TCP services to a specific outside source address and TCP port:

• switch# configure terminal
• switch(config)# ip nat outside source static tcp 20.1.9.2 63 35.48.35.48 130
• switch(config)# copy running-config startup-config

Configuring Static Twice NAT

All translations within the same group are considered for creating static twice Network Address Translation (NAT) rules.

SUMMARY STEPS

1. enable
2. configure terminal
3. ip nat inside source static inside-local-ip-address inside-global-ip-address [group group-id] [add-route]
4. ip nat outside source static outside-global-ip-address outside-local-ip-address [group group-id] [add-route]
5. interface type number
6. ip address ip-address mask
7. ip nat inside
8. exit
9. interface type number
10. ip address ip-address mask
11. ip nat outside
12. end

DETAILED STEPS

Example:

switch> enable

| Enables privileged EXEC mode.

•  Enter your password if prompted.

Step 2| configure terminal

Example:

switch# configure terminal

| Enters privileged EXEC mode.
Step 3| ip nat inside source static inside-local-ip-address inside- global-ip-address [ group group-id ] [ add-route ]

Example:

switch(config)# ip nat inside source static 10.1.1.1 192.168.34.4 group 4

| Configures static twice NAT to translate an inside local IP address to the corresponding inside global IP address.

•  The group keyword determines the group to which a translation belongs.

Step 4| ip nat outside source static outside-global-ip-address outside-local-ip-address [ group group-id ] [ add-route ]

Example:

switch(config)# ip nat outside source static 209.165.201.1 10.3.2.42 group 4 add-route

| Configures static twice NAT to translate an outside global IP address to the corresponding outside local IP address.

•  The group keyword determines the group to which a translation belongs.

Step 5| interface type number

Example:

switch(config)# interface ethernet 1/2

| Configures an interface and enters interface configuration mode.
 | Command or Action| Purpose
---|---|---
Step 6| ip address ip-address mask

Example:

switch(config-if)# ip address 10.2.4.1 255.255.255.0

| Sets a primary IP address for an interface.
Step 7| ip nat inside

Example:

switch(config-if)# ip nat inside

| Connects the interface to an inside network, which is subject to NAT.

Note **** Configuration not supported on loopback interface.

Step 8| exit

Example:

switch(config-if)# exit

| Exits interface configuration mode and returns to global configuration mode.
Step 9| interface type number

Example:

switch(config)# interface ethernet 1/1

| Configures an interface and enters interface configuration mode.
Step 10| ip address ip-address mask

Example:

switch(config-if)# ip address 10.5.7.9 255.255.255.0

| Sets a primary IP address for an interface.
Step 11| ip nat outside

Example:

switch(config-if)# ip nat outside

| Connects the interface to an outside network, which is subject to NAT.

Note **** Configuration not supported on loopback interface.

Step 12| end

Example:

switch(config-if)# end

| Exits interface configuration mode and returns to privileged EXEC mode.

Enabling and Disabling no-alias Configuration
NAT devices own Inside Global (IG) and Outside Local (OL) addresses and they are responsible for responding to any ARP requests directed to these addresses. When the IG/OL address subnet matches with the local interface subnet, NAT installs an IP alias and an ARP entry, in this case the device uses local-proxy-arp to respond to ARP requests.
The no-alias feature responds to ARP requests of all the translated IPs from a given NAT pool address range if the address range is in same subnet of the outside interface.
If no-alias is enabled on an interface with NAT configuration, the outside interface will not respond to any ARP requests in its subnet. When no-alias is disabled, the ARP requests for IPs in same subnet as of outside interface are served.

Note When you downgrade to any older releases that does not support this feature, configurations with no-alias option may be deleted.

SUMMARY STEPS

1. switch# configure terminal
2. switch(config)# feature nat
3. switch(config)# show run nat
4. switch(config)# show ip nat-alias
5. switch(config)# clear ip nat-alias ip address/all

DETAILED STEPS

mode.
Step 2| switch(config)# feature nat| Enables the static NAT feature on the device.
Step 3| switch(config)# show run nat| Displays NAT configuration.
Step 4| switch(config)# show ip nat-alias| Displays the information whether or not the alias is created.

Note **** By default, alias is created. To disable the alias, you must append no-alias keyword to the command.

Step 5| switch(config)# clear ip nat-alias ip address / all| Removes entries from alias list. To remove a specific entry you must provide the IP address that you want to remove. To remove all entries, use the all keyword.

Example

This example shows the interface information:

This example shows how to configure alias:

• switch# configure terminal
• switch(config)# ip nat pool p1 7.7.7.2 7.7.7.20 prefix-length 24
• switch(config)# ip nat inside source static 1.1.1.2 8.8.8.3
• switch(config)# ip nat outside source static 2.2.2.1 7.7.7.3
• switch(config)# show ip nat-alias

Alias Information for Context: default

This example shows the output of show ip nat-alias. By default, alias is enabled.

• switch# configure terminal
• switch(config)# show ip nat-alias

Alias Information for Context: default

This example shows how to disable alias:

• switch# configure terminal
• switch(config)# ip nat pool p1 7.7.7.2 7.7.7.20 prefix-length 24 no-alias
• switch(config)# ip nat inside source static 1.1.1.2 8.8.8.3 no-alias
• switch(config)# ip nat outside source static 2.2.2.1 7.7.7.3 no-alias
• switch(config)# show ip nat-alias

Alias Information for Context: default

None of the entry got appended as alias is disabled for above CLIs.

switch(config)#
This example shows how to clear alias. Use clear ip nat-alias to remove an entry from alias list. You can remove a single entry by specifying the IP address or remove all the alias entries.

Configuration Example for Static NAT and PAT
This example shows the configuration for static NAT:

• ip nat inside source static 103.1.1.1 11.3.1.1
• ip nat inside source static 139.1.1.1 11.39.1.1
• ip nat inside source static 141.1.1.1 11.41.1.1
• ip nat inside source static 149.1.1.1 95.1.1.1
• ip nat inside source static 149.2.1.1 96.1.1.1
• ip nat outside source static 95.3.1.1 95.4.1.1
• ip nat outside source static 96.3.1.1 96.4.1.1
• ip nat outside source static 102.1.2.1 51.1.2.1
• ip nat outside source static 104.1.1.1 51.3.1.1
• ip nat outside source static 140.1.1.1 51.40.1.1

This example shows the configuration for static PAT:

• ip nat inside source static tcp 10.11.1.1 1 210.11.1.1 101
• ip nat inside source static tcp 10.11.1.1 2 210.11.1.1 201
• ip nat inside source static tcp 10.11.1.1 3 210.11.1.1 301
• ip nat inside source static tcp 10.11.1.1 4 210.11.1.1 401
• ip nat inside source static tcp 10.11.1.1 5 210.11.1.1 501
• ip nat inside source static tcp 10.11.1.1 6 210.11.1.1 601
• ip nat inside source static tcp 10.11.1.1 7 210.11.1.1 701
• ip nat inside source static tcp 10.11.1.1 8 210.11.1.1 801
• ip nat inside source static tcp 10.11.1.1 9 210.11.1.1 901
• ip nat inside source static tcp 10.11.1.1 10 210.11.1.1 1001
• ip nat inside source static tcp 10.11.1.1 11 210.11.1.1 1101
• ip nat inside source static tcp 10.11.1.1 12 210.11.1.1 1201

Example: Configuring Static Twice NAT

The following example shows how to configure the inside source and outside source static twice NAT configurations:

• Switch> enable
• Switch# configure terminal
• Switch(config)# ip nat inside source static 10.1.1.1 192.168.34.4 group 4
• Switch(config)# ip nat outside source static 209.165.201.1 10.3.2.42 group 4
• Switch(config)#  interface ethernet 1/2
• Switch(config-if)# ip address 10.2.4.1 255.255.255.0
• Switch(config-if)# ip nat inside
• switch(config-if)# exit
• switch(config)# interface ethernet 1/1
• switch(config-if)# ip address 10.5.7.9 255.255.255.0
• switch(config-if)# ip nat outside
• Switch(config-if)# end

Verifying the Static NAT Configuration

To display the static NAT configuration, perform this task:

SUMMARY STEPS

1. switch# show ip nat translations

DETAILED STEPS

for the inside global, inside local, outside local, and outside global IP addresses.

Example
This example shows how to display the static NAT configuration:

Configuring Dynamic NAT

Configuring Dynamic Translation and Translation Timeouts

SUMMARY STEPS

1. enable
2. configure terminal
3. ip access-list access-list-name
4. permit protocol source source-wildcard any
5. deny protocol source source-wildcard any
6. exit
7. ip nat inside source list access-list-name interface type number [vrf vrf-name [match-in-vrf] overload]
8. interface type number
9. ip address ip-address mask
10. ip nat inside
11. exit
12. interface type number
13. ip address ip-address mask
14. ip nat outside
15. exit
16. ip nat translation max-entries number-of-entries
17. ip nat translation timeout seconds
18. ip nat translation creation-delay seconds
19. ip nat translation icmp-timeout seconds
20. end

DETAILED STEPS

Example:

Switch> enable

| Enables privileged EXEC mode.

•  Enter your password if prompted.

Step 2| configure terminal

Example:

Switch# configure terminal

| Enters global configuration mode.
Step 3| ip access-list access-list-name

Example:

Switch(config)# ip access-list acl1

| Defines an access list and enters access-list configuration mode.
 | Command or Action| Purpose
---|---|---
Step 4| permit protocol source source-wildcard any

Example:

Switch(config-acl)# permit ip 10.111.11.0/24 any

| Sets conditions in an IP access list that permit traffic matching the conditions.
Step 5| deny protocol source source-wildcard any

Example:

Switch(config-acl)# deny udp 10.111.11.100/32 any

| Sets conditions in an IP access list that deny packets from entering a network.
Step 6| exit

Example:

Switch(config-acl)# exit

| Exits access-list configuration mode and returns to global configuration mode.
Step 7| ip nat inside source list access-list-name interface type number [ vrf vrf-name [ match-in-vrf ] overload ]

Example:

Switch(config)# ip nat inside source list acl1 interface ethernet 1/1 overload

| Establishes dynamic source translation by specifying the access list defined in Step 3.
Step 8| interface type number

Example:

Switch(config)# interface ethernet 1/4

| Configures an interface and enters interface configuration mode.
Step 9| ip address ip-address mask

Example:

Switch(config-if)# ip address 10.111.11.39 255.255.255.0

| Sets a primary IP address for the interface.
Step 10| ip nat inside

Example:

Switch(config-if)# ip nat inside

| Connects the interface to an inside network, which is subject to NAT.

Note **** Configuration not supported on loopback interface.

Step 11| exit

Example:

Switch(config-if)# exit

| Exits interface configuration mode and returns to global configuration mode.
Step 12| interface type number

Example:

Switch(config)# interface ethernet 1/1

| Configures an interface and enters interface configuration mode.
Step 13| ip address ip-address mask

Example:

Switch(config-if)# ip address 172.16.232.182 255.255.255.240

| Sets a primary IP address for an interface.
 | Command or Action| Purpose
---|---|---
Step 14| ip nat outside

Example:

Switch(config-if)# ip nat outside

| Connects the interface to an outside network.

Note **** Configuration not supported on loopback interface.

Step 15| exit

Example:

Switch(config-if)# exit

| Exits interface configuration mode and returns to global configuration mode.
Step 16| ip nat translation max-entries number-of-entries

Example:

Switch(config)# ip nat translation max-entries 300

| Specifies the maximum number of dynamic NAT translations. The number of entries can be between 1 and 1023.
Step 17| ip nat translation timeout seconds

Example:

switch(config)# ip nat translation timeout 13000

| Specifies the timeout value for dynamic NAT translations.
Step 18| ip nat translation creation-delay seconds

Example:

switch(config)# ip nat translation creation-delay 250

| Specifies the ICMP timeout value for dynamic NAT translations.

Note **** To reduce the frequency of programming the NAT entries in the hardware, NAT batches and programs the translations for one second. Frequently programming the hardware burdens the CPU but delaying the programming delays establishing sessions.

You can disable batching or reduce the

creation delay using this command. It is not recommended to set creation delay to 0.

Step 19| ip nat translation icmp-timeout seconds

Example:

switch(config)# ip nat translation icmp-timeout 100

| Specifies the ICMP timeout value for dynamic NAT translations.
Step 20| end

Example:

Switch(config)# end

| Exits global configuration mode and returns to privileged EXEC mode.

Configuring Dynamic NAT Pool

You can create a NAT pool by either defining the range of IP addresses in a single ip nat pool command or by using the ip nat pool and address commands

SUMMARY STEPS

1. switch# configure terminal
2. switch(config)# feature nat
3. switch(config)# ip nat pool pool-name [startip endip] {prefix prefix-length | netmask network-mask}
4. (Optional) switch(config-ipnat-pool)# address startip endip
5. (Optional) switch(config)# no ip nat pool pool-name

DETAILED STEPS

mode.
Step 2| switch(config)# feature nat| Enables the NAT feature on the device.
Step 3| switch(config)# ip nat pool pool-name [ startip endip ]

{ prefix prefix-length | netmask network-mask }

| Creates a NAT pool with a range of global IP addresses.

The IP addresses are filtered by using either a prefix length or a network mask.

Step 4| (Optional) switch(config-ipnat-pool)# address startip endip| Specifies the range of global IP addresses if they were not specified during creation of the pool.
Step 5| (Optional) switch(config)# no ip nat pool pool-name| Deletes the specified NAT pool.

Example

This example shows how to create a NAT pool with a prefix length:

• switch# configure terminal
• switch(config)# ip nat pool pool1 30.1.1.1 30.1.1.2 prefix-length 24
• switch(config)#

This example shows how to create a NAT pool with a network mask:

• switch# configure terminal
• switch(config)# ip nat pool pool5 20.1.1.1 20.1.1.5 netmask 255.0.255.0
• switch(config)#

This example shows how to create a NAT pool and define the range of global IP addresses using the ip nat pool and address commands:

• switch# configure terminal
• switch(config)# ip nat pool pool7 netmask 255.255.0.0
• switch(config-ipnat-pool)# address 40.1.1.1 40.1.1.5
• switch(config-ipnat-pool)#

This example shows how to delete a NAT pool:

• switch# configure terminal
• switch(config)# no ip nat pool pool4
• switch(config)#

Configuring Source Lists

You can configure a source list of IP addresses for the inside interface and the outside interface.

Before you begin
Ensure that you configure a pool before configuring the source list for the pool.

SUMMARY STEPS

1. switch# configure terminal
2. (Optional) switch# ip nat inside source list list-name pool pool-name [overload]
3. (Optional) switch# ip nat outside source list list-name pool pool-name [add-route]

DETAILED STEPS

mode.
Step 2| (Optional) switch# ip nat inside source list list-name pool

pool-name [ overload ]

| Creates a NAT inside source list with pool with or without overloading.
Step 3| (Optional) switch# ip nat outside source list list-name

pool pool-name [ add-route ]

| Creates a NAT outside source list with pool without overloading.

Example

This example shows how to create a NAT inside source list with pool without overloading:

• switch# configure terminal
• switch(config)# ip nat inside source list list1 pool pool1
• switch(config)#

This example shows how to create a NAT inside source list with pool with overloading:

• switch# configure terminal
• switch(config)# ip nat inside source list list2 pool pool2 overload
• switch(config)#

This example shows how to create a NAT outside source list with pool without overloading:

• switch# configure terminal
• switch(config)# ip nat outside source list list3 pool pool3
• switch(config)#

Configuring Dynamic Twice NAT for an Inside Source Address
For an inside source address translation, the traffic flows from the inside interface to the outside interface. You can configure dynamic twice NAT for an inside source address.

Before you begin
Ensure that you enable NAT on the switch.

SUMMARY STEPS

1. switch# configure terminal
2. switch(config)# ip nat outside source static outside-global-ip-address outside-local-ip-address | [tcp |udp] outside-global-ip-address outside-global-port outside-local-ip-address outside-local-port [group group-id] [dynamic] [add-route]
3. switch(config)# ip nat inside source list access-list-name [interface type slot/port overload | pool pool-name overload] [group group-id] [dynamic] [add-route]
4. switch(config)# ip nat pool pool-name [startip endip] {prefix prefix-length | netmask network-mask}
5. switch(config)# interface type slot/port
6. switch(config-if)# ip nat outside
7. switch(config-if)# exit
8. switch(config)# interface type slot/port
9. switch(config-if)# ip nat inside

DETAILED STEPS

mode.
Step 2| switch(config)# ip nat outside source static

outside-global-ip-address outside-local-ip-address | [ tcp | udp ] outside-global-ip-address outside-global-port outside-local-ip-address outside-local-port [ group

group-id ] [ dynamic ] [ add-route ]

| Configures static NAT to translate an outside global address to an inside local address or to translate inside local traffic to inside global traffic.

The group keyword determines the group to which a translation belongs.

Step 3| switch(config)# ip nat inside source list access-list-name [ interface type slot/port overload | pool pool-name overload ] [ group group-id ] [ dynamic ] [ add-route ]| Establishes dynamic source translation by creating a NAT inside source list with pool with or without overloading.

The group keyword determines the group to which a translation belongs.

Step 4| switch(config)# ip nat pool pool-name [ startip endip ]

{ prefix prefix-length | netmask network-mask }

| Creates a NAT pool with a range of global IP addresses.

The IP addresses are filtered by using either a prefix length or a network mask.

Step 5| switch(config)# interface type slot/port| Configures an interface and enters interface configuration mode.
Step 6| switch(config-if)# ip nat outside| Connects the interface to an outside network.
Step 7| switch(config-if)# exit| Exits interface configuration mode and returns to global configuration mode.
Step 8| switch(config)# interface type slot/port| Configures an interface and enters interface configuration mode.
 | Command or Action| Purpose
---|---|---
Step 9| switch(config-if)# ip nat inside| Connects the interface to an inside network, which is subject to NAT.

Example
This example shows how to configure dynamic twice NAT for an inside source address:

• switch# configure terminal
• Enter configuration commands, one per line. End with CNTL/Z.
• switch(config)# ip nat outside source static 2.2.2.2 4.4.4.4 group 20 dynamic switch(config)# ip nat inside source list acl_1 pool pool_1 overload group 20 dynamic
• switch(config)# ip nat pool pool_1 3.3.3.3 3.3.3.10 prefix-length 24
• switch(config)# interface Ethernet1/8
• switch(config-if)# ip nat outside
• switch(config-if)# exit
• switch(config)# interface Ethernet1/15
• switch(config-if)# ip nat inside

Configuring Dynamic Twice NAT for an Outside Source Address
For an outside source address translation, the traffic flows from the outside interface to the inside interface. You can configure dynamic twice NAT for an outside source address.

Before you begin
Ensure that you enable NAT on the switch.

SUMMARY STEPS

1. switch# configure terminal
2. switch(config)# ip nat inside source static inside-local-ip-address inside-global-ip-address | [tcp | udp] inside-local-ip-address local-port inside-global-ip-address global port [group group-id] [dynamic] [add-route]
3. switch(config)# ip nat outside source list access-list-name pool pool-name [group group-id] dynamic [add-route]
4. switch(config)# ip nat pool pool-name [startip endip] {prefix prefix-length | netmask network-mask}
5. switch(config)# interface type slot/port
6. switch(config-if)# ip nat outside
7. switch(config-if)# exit
8. switch(config)# interface type slot/port
9. switch(config-if)# ip nat inside

DETAILED STEPS

mode.
 | Command or Action| Purpose
---|---|---
Step 2| switch(config)# ip nat inside source static

inside-local-ip-address inside-global-ip-address | [ tcp |

udp ] inside-local-ip-address local-port

inside-global-ip-address global-port [ group group-id ] [ dynamic ] [ add-route ]

| Configures static NAT to translate an inside global address to an inside local address or to translate inside local traffic to inside global traffic.

The group keyword determines the group to which a translation belongs.

Step 3| switch(config)# ip nat outside source list access-list- name

pool pool-name [ group group-id ] dynamic [ add-route ]

| Establishes dynamic source translation by creating a NAT outside source list with pool with or without overloading.
Step 4| switch(config)# ip nat pool pool-name [ startip endip ]

{ prefix prefix-length | netmask network-mask }

| Creates a NAT pool with a range of global IP addresses.

The IP addresses are filtered by using either a prefix length or a network mask.

Step 5| switch(config)# interface type slot/port| Configures an interface and enters interface configuration mode.
Step 6| switch(config-if)# ip nat outside| Connects the interface to an outside network.
Step 7| switch(config-if)# exit| Exits interface configuration mode and returns to global configuration mode.
Step 8| switch(config)# interface type slot/port| Configures an interface and enters interface configuration mode.
Step 9| switch(config-if)# ip nat inside| Connects the interface to an inside network, which is subject to NAT.

Example
This example shows how to configure dynamic twice NAT for an outside source address:

• switch# configure terminal
• Enter configuration commands, one per line. End with CNTL/Z.
• switch(config)# ip nat inside source static 7.7.7.7 5.5.5.5 group 30 dynamic switch(config)# ip nat outside source list acl_1 pool pool_1 group 30 dynamic switch(config)# ip nat pool pool_2 4.4.4.4 4.4.4.10 prefix-length 24 switch(config)# interface Ethernet1/6
• switch(config-if)# ip nat outside
• switch(config-if)# exit
• switch(config)# interface Ethernet1/11
• switch(config-if)# ip nat inside

Configuring FINRST and SYN Timers
This section describes how to configure FINRST and SYN timer values. When you reload the switch, restoring or erasing the configured FINRST and/or SYN timer values depends on whether or not the TCP TCAM carved. If the TCAM is carved, the switch restores the currently configured values. If the timer values are not configured, it sets a default value of 60. If the TCAM is not carved, the switch removes any currently configured values and sets a default value as never. This is because the the TCP AWARE feature gets disabled when the TCP TCAM is not carved.

SUMMARY STEPS

1. switch# configure terminal
2. switch(config-if)# ip nat translation syn-timeout {seconds | never}
3. switch(config-if)# ip nat translation finrst-timeout {seconds | never}

DETAILED STEPS

mode.
Step 2| switch(config-if)# ip nat translation syn-timeout

{ seconds | never }

| Specifies the timeout value for TCP data packets that sends the SYN request, but do not receive a SYN-ACK reply.

The timeout value ranges from 1 to 172800 seconds. When the TCP TCAM is carved the default value is 60 seconds. When the TCP TCAM is not carved the default value is never. The never keyword deactivates SYN timer.

Note **** You cannot configure SYN timer when TCP TCAM is not carved..

Step 3| switch(config-if)# ip nat translation finrst-timeout

{ seconds | never }

| Specifies the timeout value for the flow entries when a

connection is terminated by receiving finish (FIN) or reset (RST) packets. You must use the configure the behavior

for both RST and FIN. The timeout value ranges from 1 to 172800 seconds. When the TCP TCAM is carved the default value is 60 seconds. When the TCP TCAM is not carved the default value is never. The never keyword deactivates FIN or RST timers.

Note **** You cannot configure FINRST timer when TCP TCAM is not carved..

Example
The following example that shows when TCP TCAM is carved
switch(config)# ip nat translation syn-timeout 20

The following example that shows when TCP TCAM is not carved
switch(config)# ip nat translation syn-timeout 20 Error: SYN TIMER CONFIG FAILED.TCP TCAM NOT CONFIGURED

Clearing Dynamic NAT Translations

To clear dynamic translations, perform the following task:

global-ip-address local-ip-address [ outside local-ip-address global- ip-address ] | outside local-ip-address global-ip-address ]

| Deletes all or specific dynamic NAT translations.

Example
This example shows how to clear all dynamic translations:
switch# clear ip nat translation all

This example shows how to clear dynamic translations for inside and outside addresses:
switch# clear ip nat translation inside 2.2.2.2 4.4.4.4 outside 5.5.5.5 7.7.7.7

Verifying Dynamic NAT Configuration

To display dynamic NAT configuration, perform the following tasks:

(NAT) translations.

Displays additional information for each translation table entry, including when an entry was created and used.

show run nat| Displays NAT configuration.
show ip nat max| Displays active Network Address Translation (NAT) maximum values.
show ip nat statistics| Monitor NAT statistics.

Example

This example shows how to display IP NAT Max values:
switch# show ip nat max
IP NAT Max values

Max Dyn Translations:80
Max all-host:0
No.Static:0
No.Dyn:1
No.Dyn-ICMP:1

Switch(config)#

This example shows how to display NAT Statistics:

switch# show ip nat statistics

No.Dyn-ICMP field is to display the no of icmp dynamic translations , its a subset of “No.Dyn” field.

Note Beginning with Cisco NX-OS Release 9.3(5), the No.Dyn-ICMP field is a subset of No.Dyn field and it displays the number of ICMP dynamic translations.

This example shows how to display running configuration for NAT: switch# show run nat

This example shows how to display active NAT translations:

Inside pool with overload

Example: Configuring Dynamic Translation and Translation Timeouts

The following example shows how to configure dynamic overload Network Address Translation (NAT) by specifying an access list:

• Switch> enable
• Switch# configure terminal
• Switch(config)# ip access-list acl1
• Switch(config-acl)# permit ip 10.111.11.0/24 any
• Switch(config-acl)# deny udp 10.111.11.100/32 any
• Switch(config-acl)# exit
• Switch(config)# ip nat inside source list acl1 interface ethernet 1/1 overload
• Switch(config)# interface ethernet 1/4
• Switch(config-if)# ip address 10.111.11.39 255.255.255.0
• Switch(config-if)# ip nat inside
• Switch(config-if)# exit
• Switch(config)# interface ethernet 1/1
• Switch(config-if)# ip address 172.16.232.182 255.255.255.240
• Switch(config-if)# ip nat outside
• Switch(config-if)# exit
• Switch(config)# ip nat translation max-entries 300
• Switch(config)# ip nat translation timeout 13000
• Switch(config)# end

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