CISCO Catalyst SD-WAN BFD for Routing Protocols User Guide

BFD for Routing Protocols in Cisco Catalyst SD-WAN

Catalyst SD-WAN BFD for Routing Protocols

Note
To achieve simplification and consistency, the Cisco SD-WAN solution has been rebranded as Cisco Catalyst SD-WAN. In addition, from Cisco IOS XE SD-WAN Release 17.12.1a and Cisco Catalyst SD-WAN Release 20.12.1, the following component changes are applicable: Cisco vManage to Cisco Catalyst SD-WAN Manager, Cisco vAnalytics to Cisco Catalyst SD-WAN Analytics, Cisco vBond to Cisco Catalyst SD-WAN Validator, and Cisco vSmart to Cisco Catalyst SD-WAN Controller. See the latest Release Notes for a comprehensive list of all the component brand name changes. While we transition to the new names, some inconsistencies might be present in the documentation set because of a phased approach to the user interface updates of the software product.

Table 1: Feature History

BFD for Routing Protocols in Cisco
Catalyst SD-WAN| Cisco IOS XE Catalyst SD-WAN
Release 17.3.1a
Cisco vManage Release 20.3.1| This feature extends BFD support to BGP, OSPF, and EIGRP protocols in the Cisco Catalyst SD-WAN solution. BFD provides
a consistent failure detection method to detect forwarding path failures at a uniform rate, therefore enabling faster reconvergence time.

• Information About BFD for Routing Protocols, on page 2
• Configure BFD for Routing Protocols, on page 5
• Configure BFD for Routing Protocols Using CLI, on page 10
• Monitor and Verify BFD Configuration, on page 12
• Troubleshoot Common BFD Errors, on page 13

Information About BFD for Routing Protocols

Overview of BFD
In enterprise networks, the convergence of business-critical applications onto a common IP infrastructure is becoming more common. Given how critical data is, these networks are typically constructed with a high degree of redundancy. While such redundancy is desirable, its effectiveness is dependent upon the ability of individual network devices to quickly detect failures and reroute traffic to an alternate path. The detection times in existing protocols are typically greater than one second, and sometimes much longer. For some applications, this duration is too long to be useful. This is where Bi- directional Forwarding Detection (BFD) comes in.
BFD provides rapid failure detection times between forwarding engines, while maintaining low overhead. It also provides a single, standardized method of link/device/protocol failure detection at any protocol layer and over any media, thus enabling faster reconvergence of business-critical applications.

Benefits of Configuring BFD for Routing Protocols

• Fast failure detection times for all media types, encapsulations, topologies, and routing protocols
• Faster reconvergence of applications
• Consistent method of failure detection

How BFD Works in Cisco Catalyst SD-WAN
With the introduction of this feature, the Cisco Catalyst SD-WAN solution now has two types of BFDs that are distinct features that work independently without conflict.

• BFD Support for Cisco Catalyst SD-WAN Routing Protocols (Legacy BFD): This feature is termed as legacy BFD because is already available for Cisco IOS XE and is being extended to the Cisco Catalyst SD-WAN solution starting Cisco IOS XE Catalyst SD-WAN Release 17.3.1a.
• Cisco Catalyst SD-WAN BFD: This feature is specific to overlay BFD, which is an existing feature in Cisco Catalyst SD-WAN.
  For more information on Cisco Catalyst SD-WAN BFD, see Cisco Catalyst SD-WAN BFD.

Table 2: Differences: BFD for Cisco Catalyst SD-WAN Routing Protocols Versus Cisco Catalyst SD-WAN BFD

BFD for Cisco Catalyst SD-WAN Routing Protocols| Cisco Catalyst SD-WAN BFD
---|---
• Runs on both, transport-side and service-side interfaces
• The following protocols can be registered: BGP, OSPF, and EIGRP
• BGP (transport and service side
• EIGRP (service side)
• OSPF and OSPFv3 (service side)
• Detects link failures for peers in terms of whether a peer is up or down| • Runs on a Cisco Catalyst SD-WAN tunnel to detect failures in the overlay tunnel
• Is enabled by default and cannot be disabled
• Is typically enabled for OMP
• Besides link failures, it also measures latency, loss, and other link statistics used by application-aware routing

Note
The rest of this document is specific to BFD for Routing Protocols in Cisco Catalyst SD-WAN (legacy BFD).

As represented in the image, BFD is configured for a routing protocol through Cisco SD-WAN Manager.
Cisco SD-WAN Manager then pushes this configuration to the edge router. In this example, let’s assume that OSPF is configured to receive forwarding path detection failure messages from BFD. If there’s a physical link failure, OSPF is prompted to shut down its neighbors and restore any routing information it may have advertised to or received from its remote neighbors.
Similarly, the router, Edge 1 is connected to the internet router through its transport interface. BFD is configured for BGP between the transport side of Edge 1 and the internet router. Here, BFD detects the health of the connection and reports any failures.

Supported Protocols and Interfaces

Supported Protocols
The following routing protocols in Cisco Catalyst SD-WAN can be configured to receive forwarding path detection failure messages from BFD:

• BGP
• EIGRP
• OSPF and OSPFv3

Supported Interfaces

• GigabitEthernet
• TenGigabitEthernet
• FiveGigabitEthernet
• FortyGigabitEthernet
• HundredGigabitEthernet
• SVI
• Subinterfaces

Limitations and Restrictions

The following restrictions apply to Cisco IOS XE Catalyst SD-WAN devices in controller mode.

• Only single-hop BFD is supported.
• BFD is not supported for static routes.
• To change the BFD session modes between software mode and hardware mode, you need to remove all existing BFD configuration and reconfigure it.
• BFD is only supported for BGP, EIGRP, OSPF, and OSPFv3.
• BFD for routing protocols in Cisco Catalyst SD-WAN cannot be monitored through Cisco SD-WAN Manager. Use CLI show commands for monitoring BFD for Cisco Catalyst SD-WAN routing protocols.
• Once a BFD session is established, BFD session modes (echo to no echo, and vice-versa; or software to hardware, and vice-versa) don’t update immediately after changing the BFD template parameters in Cisco SD-WAN Manager. The BFD mode change takes effect only after the session flaps at least once.

Configure BFD for Routing Protocols

Cisco SD-WAN Manager does not provide an independent template to configure BFD for routing protocols.
However, supported protocols can be registered or deregistered to received BFD packets by adding configurations using the CLI add-on template in Cisco SD-WAN Manager. Use the CLI add-on template to configure the following:

• Add a single-hop BFD template with parameters such as timer, multiplier, session mode, and so on.
• Enable the BFD template under interfaces. Only one BFD template can be added per interface.
• Enable or disable BFD for the supported routing protocols. The configuration to enable or disable BFD is different for each of the supported routing protocols: BGP, EIGRP, OSPF, and OSPFv3.

Enable BFD for Routing Protocols
Configure BFD for Service-Side BGP

1. From the Cisco SD-WAN Manager menu, choose Configuration > Templates.

2. Click Feature Templates.
   Note In Cisco vManage Release 20.7.x and earlier releases, Feature Templates is titled Feature.

3. Click Add Template.

4. Choose a device from the device list.

5. Choose the CLI Add-on Template under Other Templates.

6. Enter the CLI configuration to add a single-hop BFD template and to enable BFD for service-BGP as shown in the following example.
   bfd-template single-hop t1 interval min-tx 500 min-rx 500 multiplier 3
   ！interface GigabitEthernet1 bfd template t1 router bgp 10005 address-family ipv4 vrf 1
   neighbor 10.20.24.17 fall-over bfd
   ! address-family ipv6 vrf 1 neighbor 2001::7 fall-over bfd
   Understanding the CLI Configuration
   In this example, a single hop BFD template is created specifying the minimum and maximum interval and the multiplier. Specifying these parameters is mandatory. In addition, you have the option to also specify other BFD parameters such as echo mode (enabled by default), and BFD dampening (off by default). Once created, the BFD template is enabled under an interface (GigabitEthernet1, in this example).
   Note
   To modify a BFD template enabled on an interface, you need to remove the existing template first, modify it, and then enable it on the interface again.
   Note
   If you attach the BFD configuration to a device template that already has a BGP feature template attached, ensure that you update the BGP configuration in the CLI add-on template to include the no neighbor ip-address ebgp-multihop command. This change is required because the neighbor ip-address ebgp-multihop command is activated on the BGP feature template by default.

7. Click Save.

8. Attach Feature Template to Device Template
   Note For the configuration to take effect, the device template must have a BGP feature template attached to it.

9. Attach the device template to the device.

Configure BFD for Transport-Side BGP

1. From the Cisco SD-WAN Manager menu, choose Configuration > Templates.

2. Click Feature Templates.
   Note In Cisco vManage Release 20.7.x and earlier releases, Feature Templates is titled Feature.

3. Click Add Template.

4. Choose a device from the device list.

5. Choose the CLI Add-on Template under Other Templates.

6. Enter the CLI configuration to add a single-hop BFD template and to enable BFD for transport-BGP as shown in the following example:
   bfd-template single-hop t1
   interval min-tx 500 min-rx 500 multiplier 3
   ! interface GigabitEthernet1 bfd template t1
   ! router bgp 10005 neighbor 10.1.15.13 fall-over bfd
   ！sdwan interface GigabitEthernet1 tunnel-interface
   allow-service bfd
   allow-service bgp
   Understanding the CLI Configuration
   In this example, a single hop BFD template is created specifying the minimum and maximum interval and the multiplier. Specifying these parameters is mandatory. In addition, you have the option to also specify other BFD parameters such as echo mode (enabled by default), and BFD dampening (off by default). Once created, the BFD template is enabled under an interface (GigabitEthernet1, in this example).
   In this example, GigabitEthernet1 is also the source of the SD-WAN tunnel. Allowing service under the tunnel interface of GigabitEthernet1 ensures that BGP and BFD packets pass over the tunnel.
   Note
   To modify a BFD template enabled on an interface, you need to remove the existing template first, modify it, and then enable it on the interface again.
   Note
   If you attach the BFD configuration to a device template that already has a BGP feature template attached, ensure that you update the BGP configuration in the CLI add-on template to include the no neighbor ip-address ebgp-multihop command. This change is required because the neighbor ip-address ebgp-multihop command is activated on the BGP feature template by default.

7. Click Save.

8. Attach Feature Template to Device Template
   Note For the configuration to take effect, the device template must have a BGP feature template attached to it.

9. Attach the device template to the device.

Configure BFD for Service-Side EIGRP

1. From the Cisco SD-WAN Manager menu, choose Configuration > Templates.

2. Click Feature Templates.
   Note In Cisco vManage Release 20.7.x and earlier releases, Feature Templates is titled Feature.

3. Click Add Template.

4. Choose a device from the device list.

5. Choose the CLI Add-on Template under Other Templates.

6. Enter the CLI configuration to add a single-hop BFD template enable BFD for EIGRP as shown in the example below.
   bfd-template single-hop t1 interval min-tx 500 min-rx 500 multiplier 3
   ！interface GigabitEthernet5 bfd template t1 router eigrp myeigrp address- family ipv4 vrf 1 autonomous-system 1 af-interface GigabitEthernet5 bfd
   Understanding the CLI Configuration
   In this example, a single hop BFD template is created specifying the minimum and maximum interval and the multiplier. Specifying these is mandatory. In addition, you have the option to also specify other BFD parameters such as echo mode (enabled by default), and BFD dampening (off by default). Once created, the BFD template is enabled under an interface (GigabitEthernet5, in this example).
   Note To modify a BFD template enabled on an interface, you first need to remove the existing template, modify it, and enable it on the interface again.

7. Click Save.

8. Attach Feature Template to Device Template
   Note For the configuration to take effect, the device template must have an EIGRP feature template attached to it.

9. Attach the device template to the device.

Configure BFD for Service-Side OSPF and OSPFv3

1. From the Cisco SD-WAN Manager menu, choose Configuration > Templates.

2. Click Feature Templates.
   Note In Cisco vManage Release 20.7.x and earlier releases, Feature Templates is titled Feature.

3. Click Add Template.

4. Choose a device from the device list.

5. Choose the CLI Add-on Template under Other Templates.

6. Enter the CLI configuration to add a single-hop BFD template enable BFD for OSPF and OSPFv3 as shown in the examples below.
   OSPF
   bfd-template single-hop t1 interval min-tx 500 min-rx 500 multiplier 3
   ! interface GigabitEthernet5 bfd template t1
   ！interface GigabitEthernet1 bfd template t1
   ! router ospf 1 vrf 1 bfd all-interfaces
   !
   OSPFv3
   bfd-template single-hop t1 interval min-tx 500 min-rx 500 multiplier 3 interface GigabitEthernet5 bfd template t1 router ospfv3 1 address-family ipv4 vrf 1 bfd all-interfaces
   Understanding the CLI Configuration
   In these examples, a single hop BFD template is created specifying the minimum and maximum interval and the multiplier. Specifying these is mandatory. In addition, you have the option to also specify other BFD parameters such as echo mode (enabled by default), and BFD dampening (off by default).
   Once created, the BFD template is enabled under an interface (GigabitEthernet5, in this example).
   Note
   To modify a BFD template enabled on an interface, you first need to remove the existing template, modify it, and enable it on the interface again.

7. Click Save.

8. Attach the CLI Add-on Template with this configuration to the device template.
   Note For the configuration to take effect, the device template must have an OSPF feature template attached to it.

9. Attach the device template to the device.

Attach Feature Template to Device Template

After creating a CLI add-on template to enable BFD, attach the template to the device template for the configuration to take effect. Follow this procedure to attach the configuration to a device template. Ensure that the device template you attach the feature template to already has the relevant feature template (BGP, OSPF, EIGRP) attached to it.

1. From the Cisco SD-WAN Manager menu, choose Configuration > Templates.

2. Click Device Templates.
   Note In Cisco vManage Release 20.7.x and earlier releases, Device Templates is titled Device.

3. Click Create Template and choose From Feature Template from the drop-down options.

4. From the Device Model drop-down options, choose a device. Enter a name and description for the template.

5. Click Create.

6. Click Additional Templates.

7. In the CLI Add-on Template field, choose the CLI add-on template you configured to enable BFD for routing protocols.

8. Click Create.
   Next: Attach device template to device

Configure BFD for Routing Protocols Using CLI

To configure BFD for BGP, EIGRP, OSPF, and OSPF3 using device CLI, follow the steps in this topic.

Create BFD Template
Create a single-hop BFD template as shown in the example below.
bfd-template single-hop t1
interval min-tx 500 min-rx 500 multiplier 3
Note The CLI configuration for creating a BFD template remains the same irrespective of the protocol you configure it for.

Enable BFD for Service-Side BGP
This example shows that BGP is configured, BFD is enabled on the interface under VRF 1, and then on service-side BGP.
interface GigabitEthernet5 bfd template t1
! router bgp 10005
bgp log-neighbor-changes
distance bgp 20 200 20
! address-family ipv4 vrf 1
bgp router-id 10.20.24.15
redistribute connected
neighbor 10.20.24.17 remote-as 10007
neighbor 10.20.24.17 activate
neighbor 10.20.24.17 send-community both
neighbor 10.20.24.17 maximum-prefix 2147483647 100
neighbor 10.20.24.17 fall-over bfd
exit-address-family
!
address-family ipv6 vrf 1
bgp router-id 10.20.24.15
neighbor 2001::7 remote-as 10007
neighbor 2001::7 activate
neighbor 2001::7 send-community both
neighbor 2001::7 maximum-prefix 2147483647 100
neighbor 2001::7 fall-over bfd
exit-address-family

Enable BFD for Transport-Side BGP
interface GigabitEthernet1
bfd template t1
!
router bgp 10005
bgp router-id 10.1.15.15
bgp log-neighbor-changes
distance bgp 20 200 20
neighbor 10.1.15.13 remote-as 10003
neighbor 10.1.15.13 fall-over bfd
address-family ipv4 unicast
neighbor 10.1.15.13 remote-as 10003
neighbor 10.1.15.13 activate
neighbor 10.1.15.13 maximum-prefix 2147483647 100
neighbor 10.1.15.13 send-community both
redistribute connected
exit-address-family
!
timers bgp 60 180
sdwan
interface GigabitEthernet1
tunnel-interface
allow-service bgp
allow-service bfd

Enable BFD for EIGRP
This example shows that EIGRP is configured, BFD is enabled on the interface under VRF 1, and then on service-side EIGRP.
interface GigabitEthernet5
bfd template t1
! router eigrp myeigrp address-family ipv4 vrf 1 autonomous-system 1
af-interface GigabitEthernet5
no dampening-change
no dampening-interval
hello-interval 5
hold-time 15
split-horizon bfd
exit-af-interface !
network 10.20.24.0 0.0.0.255 topology base
redistribute connected redistribute omp exit-af-topology
! exit-address-family
!

Enable BFD for OSPFv3
This example shows that OSPFv3 is configured, BFD is enabled on the interface under VRF 1, and then on service-side EIGRP.
interface GigabitEthernet5
bfd template t1
ospfv3 1 ipv4 area 0
ospfv3 1 ipv4 dead-interval 40
ospfv3 1 ipv4 hello-interval 10
ospfv3 1 ipv4 network broadcast
ospfv3 1 ipv4 priority 1
ospfv3 1 ipv4 retransmit-interval 5
ospfv3 1 ipv6 area 0
ospfv3 1 ipv6 dead-interval 40
ospfv3 1 ipv6 hello-interval 10
ospfv3 1 ipv6 network broadcast
ospfv3 1 ipv6 priority 1
ospfv3 1 ipv6 retransmit-interval 5

router ospfv3 1
address-family ipv4 vrf 1
area 0 normal
bfd all-interfaces
router-id 10.20.24.15
distance 110
exit-address-family
!
address-family ipv6 vrf 1
area 0 normal
bfd all-interfaces
router-id 10.20.24.15
distance 110
exit-address-family
!
!
exit

Monitor and Verify BFD Configuration

This sections provides a list of commands that you can run to verify your BFD configuration.
Run the show bfd interface command to check the BFD template under an interface.
Device# show bfd interface
Interface Name: GigabitEthernet5
Interface Number: 11
Configured bfd interval using bfd template: 12383_4T1
Min Tx Interval: 50000, Min Rx Interval: 50000, Multiplier: 3

Verify BFD Configuration for BGP
Run the show bfd neighbors client bgp ipv4 command to check the status of the BFD session.
Device# show bfd neighbors client bgp ipv4

Verify BFD Configuration for EIGRP
Run the show bfd neighbors client eigrp command to check the status of the BFD session.

Verify BFD Configuration for OSPF
Run the show bfd neighbors client ospf command to check the status of the BFD session.

Troubleshoot Common BFD Errors

Check Control Connections
If you experience issues with BFD, start by checking the control connection between Cisco SD-WAN Manager and the edge router by running the show sdwan control connections command.

Issues in Pushing Device Template to Device
If you identify issues with pushing the device template to the device, collect debug logs on the edge device as shown below.
debug netconf all
request platform soft system shell
tail -f /var/log/confd/cia-netconf-trace.log
If Cisco SD-WAN Manager has successfully pushed the configuration to the device and the issue still persists, run the show sdwan running-config command to view all details related to BFD.

Issues with Transport-Side BFD
If the transport-side BFD session is down, check the packet filter data under the Cisco Catalyst SD-WAN tunnel interface to ensure that you have allowed the BFD packets to pass through on the transport side. Look for allow-service bgp and allow-service bfd in the output.
Device#show sdwan running-config | sec sdwan tunnel mode sdwan sdwan
interface GigabitEthernet1 tunnel-interface encapsulation ipsec color lte
allow-service bgp
allow-service bfd
……………

References

• Cisco Catalyst SD-WAN Routing Configuration Guide, Cisco IOS XE Catalyst SD-WAN Release 17.x - BFD for Routing Protocols in Cisco Catalyst SD-WAN [Cisco SD-WAN] - Cisco
• Cisco Catalyst SD-WAN Systems and Interfaces Configuration Guide, Cisco IOS XE Catalyst SD-WAN Release 17.x - Configure Devices [Cisco SD-WAN] - Cisco
• Cisco Catalyst SD-WAN Routing Configuration Guide, Cisco IOS XE Catalyst SD-WAN Release 17.x - Cisco Catalyst SD-WAN BFD [Cisco SD-WAN] - Cisco

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