SONICWALL SonicOS 7.1 DNS Network User Guide

SonicOS comes equipped with several features to configure Network. Basic Network information can be viewed in the Dashboard (navigate to HOME > Dashboard>System). The other Network configuration tools are group under the NETWORK option as follows.

• System – To manage the Network settings.
• Firewall – To manage the Firewall settings and to view the connections.
• VoIP – To manage the General settings and to view call status.
• DNS – To configure DNS settings, Dynamic DNS, and DNS Proxy settings.
• SD-WAN – To configure SD-WAN groups.
• IPSec VPN – To configure IPSec VPN settings.
• SSL VPN – To configure SSL VPN settings.

DNS Introduction

The Domain Name System (DNS) is a distributed, hierarchical system that provides a method for identifying hosts on the Internet using alphanumeric names called fully qualified domain names (FQDNs) instead of using difficult to remember numeric IP addresses.

The DNS tools are group under the NETWORK | DNS options allows you to configure DNS.

• Configuring DNS Settings
• Configuring Dynamic DNS
• Configuring DNS Proxy Settings

Configuring DNS Settings

NETWORK | DNS allows you to manually configure your DNS settings, if necessary.
The options in NETWORK | DNS > Settings change depending on whether you select IPv4 or IPv6 on the Settings tab.
To select the IP version:

1. Navigate to NETWORK | DNS > Settings.
2. On the Settings tab, select either the IPv4 or IPv6 option

Configuring DNS for IPv4
The NETWORK | DNS > Settings > IPv4 page has these sections:

• Specifying Which DNS Servers are Used
• Enabling Proxy of Split DNS Servers
• DNS Rebinding Attack Prevention
• DNS Rebinding and Cache Lookup

Specifying which DNS Servers are Used
Regardless of the IP version, you can specify how SonicOS selects the DNS servers.

To specify which DNS servers are used:

1. Navigate to NETWORK | DNS > Settings.

2. In the IPv4 DNS Settings, select one of the following:
   To manually specify the DNS servers:
   1. Select Specify DNS Servers Manually.
   2. Enter up to three IP addresses into the DNS Server # fields. To use the DNS Settings configured for the WAN zone, select Inherit DNS Settings Dynamically from WAN Zone. This is the default. The IP address(es) are populated into the DNS Server fields automatically.

3. Click Accept to save your changes.

Enabling Proxy of Split DNS Servers
Split DNS servers are separate domain-specific DNS servers that you can use optionally with IPv6.
To enable the proxying of split DNS servers:

1. Navigate to NETWORK | DNS > Settings.
2. Select Enable proxying of split DNS servers under to the Split DNS section. This option is selected by default.
3. Click Accept.

DNS Rebinding Attack Prevention
DNS rebinding is a DNS-based attack on code embedded in web pages. Normally requests from code embedded in web pages (JavaScript, Java, and Flash) are bound to the website they are originating from (see Same Origin Policy). A DNS rebinding attack can be used to improve the ability of JavaScript-based malware to penetrate private networks and subvert the browser’s same-origin policy.
DNS rebinding attackers register a domain that is delegated to a DNS server they control. The server is configured to respond with a very short Time to Live (TTL) parameter, which prevents the result from being cached. The first response contains the IP address of the server hosting the malicious code. Any subsequent requests contain IP addresses from private (RFC 1918) network, presumably behind a firewall, being target of the attacker. Because both are fully valid DNS responses, they authorize the sandbox script to access hosts in a private network. By iterating addresses in these short-term but still valid DNS replies, the script is able to scan the network and perform other malicious activities.

To configure DNS rebinding attack prevention:

1. Navigate to NETWORK | DNS > Settings.

2. Select Enable DNS Rebinding Attack Prevention under DNS Rebinding Attack Prevention section.
   This option is not selected by default. The two options become available.

3. From the Action drop-down menu, select an action to perform when a DNS rebinding attack is detected:
   • Log Attack
   • Log Attack & Return a Query Refused Reply
   • Log Attack & Drop DNS Reply

4.  From the Allowed Domains drop-down menu, select an allowed domain FQDN Address Object or FQDN Address Object Group containing allowed domain-names (such as *.SonicWall.com) for which locally connected/routed subnets should be considered legal responses.
   You can also create new FQDN address objects or FQDN address object groups by selecting Create new FQDN Address Object Group… or Create new FQDN Address Object….

5. Click Accept.

DNS Rebinding and Cache Lookup
This section provides settings related to the prevention of DNS rebinding attacks using FQDN address objects.
DNS Binding For FQDN
To enable DNS binding for FQDN:

1. Navigate to NETWORK | DNS > Settings.
2.  Scroll to the DNS Rebinding and Cache Lookup section.
3. Under the DNS Binding for FQDN heading, select FQDN Object Only Cache DNS Reply from Sanctioned Server. This option is not selected by default.
4. Click Accept.

Enabling DNS Host Name Lookup over TCP for FQDN

By default, DNS queries are sent over UDP. The DNS response can include a Truncated flag if the response length exceeds the maximum allowed by UDP.
When the Enable DNS host name lookup over TCP for FQDN option is:

• Enabled and the Truncated flag is set in the DNS response, SonicOS sends an additional DNS query over TCP to determine the full DNS response for multiple IP addresses.
• Disabled, DNS queries are sent over UDP, and SonicOS only processes the IP addresses in the DNS response packet, although the Truncated flag is set in the response.
  The DNS query times out after one second if no DNS response over TCP is received from the DNS server.
  This option is used to gain more IP addresses when sending DNS queries from FQDN over TCP while the Security Appliance receives DNS responses over UDP.

To enable DNS host name lookup over TCP for FQDN:

1. Navigate to NETWORK | DNS > Settings.
2. Under the DNS host name lookup over TCP for FQDN heading, select Enable DNS host name lookup over TCP for FQDN. This option is not selected by default.
3. Click Accept.

DNS Cache Lookup
With the DNS Cache Lookup feature, you can view the cached names and IP addresses from DNS resolution. To show the contents of the general DNS cache, click Lookup DNS Cache. A pop-up displays the cache contents.

What| DNS Server name:
• Forward DNS cache, the host name.
• Reverse DNS cache, a string representation of the IP address.
---|---
DNS
Name| Domain name, such as www.SonicWall.com, or IP address.
IP
Address| Resolved IP address.
TTL
(secs)| Time to Live; the TTL value from the DNS response.
flush| Clicking this flushes the server’s DNS cache entry
flush all| Clicking this flushes all DNS cache entry of all listed servers

Configuring DNS for IPv6
The NETWORK | DNS > Settings > IPv6 page has these sections:

•  Specifying Which DNS Servers are Used
• Enabling Proxy of Split DNS Servers
• Enabling DNS Host Name Lookup over TCP for FQDN

Specifying which DNS Servers are Used
Regardless of the IP version, you can specify how SonicOS selects the DNS servers.
To specify which DNS servers are used:

1. Navigate to NETWORK | DNS > Settings.

2. In the IPv6 DNS Settings, select one of the following:
   • To manually specify the DNS servers:
   1. Select Specify DNS Servers Manually.
   2. Enter up to three IP addresses into the DNS Server # fields.
   • To use the DNS Settings configured for the WAN zone, select Inherit DNS Settings Dynamically from WAN Zone. This is the default. The IP address(es) are populated into the DNS Server fields automatically.

3. Select Prefer IPv6 DNS Servers to use IPv6 servers only. This option is not selected by default.
   SonicOS DNS supports these server types:
   • DNS_SYSTEM_BEHAVIOR – the system default behavior, which depends on the setting of this option.
   • DNS_PREFER_V4_DNSSERVER – IPv4 DNS servers preferred unless there is a failure, then IPv6 DNS servers are requested.
   • DNS_PREFER_V6_DNSSERVER: – IPv6 DNS servers preferred unless there is a failure, then IPv4 DNS servers are requested.
   CAUTION : Select this option only if you have configured the IPv6 DNS server correctly.

4. Click Accept to save your changes.

Enabling Proxy of Split DNS Servers
Split DNS servers are separate domain-specific DNS servers that you can use optionally with IPv6.

To enable the proxying of split DNS servers:

1. Navigate to NETWORK | DNS > Settings.
2. Select Enable proxying of split DNS servers under to the Split DNS section. This option is selected by default.
3. Click Accept.

Enabling DNS Host Name Lookup over TCP for FQDN
By default, DNS queries are sent over UDP. The DNS response can include a Truncated flag if the response length exceeds the maximum allowed by UDP.
When the Enable DNS host name lookup over TCP for FQDN option is:

• Enabled and the Truncated flag is set in the DNS response, SonicOS sends an additional DNS query over TCP to determine the full DNS response for multiple IP addresses.
• Disabled, DNS queries are sent over UDP, and SonicOSonly processes the IP addresses in the DNS response packet, although the Truncated flag is set in the response.

The DNS query times out after one second if no DNS response over TCP is received from the DNS server.
This option is used to gain more IP addresses when sending DNS queries from FQDN over TCP while the Security Appliance receives DNS responses over UDP.
To enable DNS host name lookup over TCP for FQDN:

1. Navigate to NETWORK | DNS > Settings.
2. Select Enable DNS host name lookup over TCP for FQDN. This option is not selected by default.
3. Click Accept.

Configuring Domain-Specific DNS Servers for Split DNS

You can optionally configure separate domain-specific DNS servers.

is displayed. If you use a specific DNS server (other than system DNS server) in Add Split DNS, you cannot see the DNS server status.
Local Interface| Interface assigned to the DNS Server.
Configure| Contains Edit and Delete icons for each server.

About Split DNS

Split DNS is an enhancement that allows you to configure a set of servers and associate them to a given domain name (which can be a wildcard). When SonicOS DNS Proxy receives a query that matches the domain name, the name is transmitted to the designated DNS server.
As an example, for a topology that has two firewalls with network connectivity:

• One firewall is connected to the Internet.
• Another is a VPN tunnel connected to the corporation network.
• Default DNS queries go to the public ISP DNS Server.
• All queries to *.SonicWall.com go to the DNS server located behind the VPN tunnel.

For viewing and configuring split DNS entries, see Configuring Domain-Specific DNS Servers for Split DNS.
By adding a split DNS entry, all queries to SonicWall.com are sent to the specific server (see Configuring Domain-Specific DNS Servers for Split DNS).
Multiple DNS servers could be configured to handle queries to SonicWall.com as well.

About Per-Partition DNS Servers and Split DNS
With or without authentication partitions, it is usually necessary to use a domain’s own DNS servers to resolve the names of devices in the domain, and occasionally there can also be a need to use different external DNS servers to resolve external host names. Now, with multiple authentication partitions, this situation is exacerbated as those partitions usually require using different DNS servers to resolve the host names in the different partitions.
NOTE : Use of a domain’s own DNS servers can be required unexpectedly because LDAP referrals usually give the referred server by DNS name, even when the LDAP servers are configured by IP address.
An example where different external DNS servers to resolve external host names was required involved externalusing cloud services that could not be resolved by the internal domain’s DNS servers.

The Split DNS feature is used directly by the SonicWall network security appliance to resolve the names of devices in domains without the need to enable DNS Proxy, including for multiple unrelated domains with authentication partitioning.
DNS servers configured in Split DNS (refer to Configuring Domain-Specific DNS Servers for Split DNS) are used directly for DNS lookups of host names in internal domains as follows:

• This applies for anything that has entries in the main DNS Cache of the network security appliance:
• SMTP servers
• SYSLOG servers
• Web Proxy servers and User (internal) Proxy servers
• GMS and GMS standby
• POP servers
• RADIUS authentication and accounting servers
• LDAP servers
• SSO / Terminal Services agents and RADIUS accounting clients
• If partitioning is enabled and a partition has one domain or one tree of parent/sub-domains (AKA one AD Forest), then if Split DNS servers are configured for the partition’s top-level domain, then those are copied into the internal partition structure. Those DNS servers are then used to resolve the names of agents, servers, and clients in the partition.
• If partitioning is enabled and a partition is configured with multiple separate domains (which is allowed but is not common), then no DNS servers are copied into the partition structure, relying instead on the mechanism described below.
• If partitioning is disabled or a partition has no DNS servers set, or for resolving items not associated with a partition, the DNS servers to use are selected per-request through the API provided by Split DNS.

Adding a Split DNS Server

To add domain-specific DNS servers and associate them to a given domain name:
IMPORTANT: The maximum number of entries for Split DNS is 32. If the list is full, new entries cannot be added.’

1. Navigate to NETWORK | DNS > Settings.

2. Choose the IP version from View IP Version.

3. To enable proxying of split DNS servers, select Enable proxying of split DNS servers. This option is selected by default.

4. Under the Split DNS table, click +Add. The Add Split DNS dialog displays.
   If you selected DNS Proxy, a page for it, DNS Proxy, also displays on the Add Split DNS dialog.

5. Choose the IP version:
   • IPv4
   • IPv6
   • Both

6. In the Domain Name field, enter the domain name. The name can contain a wildcard (; for example, .SonicWall.com).

7. To configure one or more IPv4/IPv6 Split DNS Servers for this domain, enter the IP addresses in the appropriate fields:
   • IPv4/IPv6 DNS Server Primary
   • IPv4/IPv6 DNS Server Secondary
   • IPv4/IPv6 DNS Server Tertiary

8. From the Local interface drop-down menu, select an interface.

9. If you have enabled DNS Proxy:
   a. To specify a Time to Live, select Manually set TTL value in DNS reply. This option is not selected by default. If this option is not selected, the TTL value is the same as that from the DNS response; if it is set, the TTL value is the same as the setting.
   NOTE : This option applies only when Split DNS is used by DNS Proxy.
   b. Enter the maximum time for the cache entry to exist. The minimum is one second, the maximum is 9999999999999999 seconds.

10. Click Save.

TIP : The DNS servers display in the Split DNS table of both IP versions regardless of which IP version was chosen when configuring them.

Editing Split DNS Entries

To edit a Split DNS entry:

1. Navigate to NETWORK | DNS > Settings.
2. In the Split DNS table, click the Edit icon associated with entry you want to edit. The Edit Split DNS dialog displays.
3. Make the changes.
4. Click Save.

Deleting Split DNS Entries
To delete a Split DNS entry:

1. In the Split DNS table, click the Delete icon in the row associated with entry you want to delete.

To delete two or more Split DNS entries:

1. In the Split DNS table, select the check boxes of the entries to be deleted. Delete becomes available.
2. Click Delete and Refresh.

To delete all Split DNS entries:

1. Click Delete All.

Configuring Dynamic DNS

Dynamic DNS (DDNS) is a service provided by various companies and organizations that allows for dynamic changing IP addresses to automatically update DNS records without manual intervention. This service allows for network access using domain names rather than IP addresses, even when the target’s IP addresses change.

About Dynamic DNS
Dynamic DNS (DDNS) is a service provided by various companies and organizations that allows for dynamic changing IP addresses to automatically update DNS records without manual intervention. This service allows for network access using domain names rather than IP addresses, even when the target’s IP addresses change. For example, is a user has a DSL connection with a dynamically assigned IP address from the ISP, the user can use DDNS to register the IP address, and any subsequent address changes, with a DDNS service provider so that external hosts can reach it using an unchanging domain name.
Dynamic DNS implementations change from one service provider to another. There is no strict standard for the method of communication, for the types of records that can be registered, or for the types of services that can be offered. Some providers offer premium versions of their services, as well, for a fee. As such, supporting a  particular DDNS provider requires explicit interoperability with that provider’s specific implementation.
Most providers strongly prefer that DDNS records only be updated when IP address changes occur. Frequent updates, particularly when the registered IP address is unchanged, may be considered abuse by providers, and could result in your DDNS account getting locked out. Refer to the use policies posted on the provider’s pages  and abide by the guidelines. SonicWall does not provide technical support for DDNS providers; the providers themselves must be contacted.
Dynamic DNS is supported for both IPv4 and IPv6.

Supported DDNS Providers
Not all services and features from all providers are supported, and the list of supported providers is subject to change. SonicOS currently supports the services from providers listed here:

dns.org| SonicOS requires a username, password, Mail Exchanger, and Backup MX to configure DDNS from Dyndns.org.
---|---
changeip.com | A single, traditional Dynamic DNS service requiring only username, password, and domain name for SonicOS configuration.
no-ip.com | Dynamic DNS service requiring only username, password, and domain name for SonicOSconfiguration. Also supports hostname grouping.
Yi.org| Dynamic DNS service requiring only username, password, and domain name for SonicOS configuration. Requires that an RR record be created on the yi.org administrative page for dynamic updates to occur properly.
Some common additional services offered by Dynamic DNS providers include:
Wildcards| Allows for wildcard references to sub-domains. For example, if you register yourdomain.dyndns.org, your site would be reachable at
*.yourdomain.dyndyn.org, for example, server.yourdomain.dyndyn.org, www.yourdomain.dyndyn.org, ftp.yourdomain.dyndyn.org.
Mail Exchangers| Creates MX record entries for your domain so that SMTP servers can locate it through DNS and send mail.
NOTE: Inbound SMTP is frequently blocked by ISPs. Check with your provider before attempting to host a mail server.
Backup MX (offered by
dns.org, yi.org)| Allows for the specification of an alternative IP address for the MX record in the event that the primary IP address is inactive.
Groups| Allows for the grouping of hosts so that an update can be performed once at the group level, rather than multiple times for each member.
Off-Line IP Address| Allows for the specification of an alternative address for your registered host names if primary registered IP is offline.

For information on setting up DDNS Profiles, refer to Configuring Dynamic DNS.
Dynamic DNS Profiles
The Dynamic DNS Profiles table provides information about configured DDNS profiles.

View IP Version| Allows you to toggle the table between IPv4 and IPv6 DDNS profiles.
---|---
Profile Name| Name assigned to the DDNS entry during its creation. This can be any value and
is used only for identification.
Domain| Fully qualified domain name (FQDN) of the DDNS entry.
Provider| DDNS provider with whom the entry is registered.
Status| Last reported/current status of the DDNS entry:
Online
DDNS entry is administratively online. The current IP setting for this entry is shown with a timestamp.
Taken Offline Locally
DDNS entry is administratively offline. If the entry is enabled, the action configured in the Offline Settings section of the Advanced page of Add DDNS Profile is taken.
Abuse
DDNS provider has considered the type or frequency of updates to be abusive. Check with the DDNS provider’s guidelines to determine what is considered abuse.
No IP change Abuse possible. A forced update without an IP address change is considered by some DDNS providers to be abusive. Automatic updates only occur when address or state changes occur. Manual or forced updates should only be made when absolutely necessary, such as when
registered information is incorrect.
Disabled
Account has been disabled because of a configuration error or a policy violation. Check the profile’s settings and verify the DDNS account status with the provider.
Invalid Account Account information provided is not valid. Check the profile’s settings and verify the DDNS account status with the provider.
Network Error Unable to communicate with the DDNS provider due to a suspected network error. Verify that the provider is reachable and online. Try the action again later.
Provider Error DDNS provider is unable to perform the requested action at this time. Check the profile’s settings and verify the DDNS account status with the provider. Try the action again later.
Not Donator
Account
Certain functions provided from certain provider, such as offline address settings, are only available to paying or donating subscribers. Check with the provider for more details on which services may require payment or donation.
Enabled| When selected, this profile is administratively enabled, and the network security appliance takes the Online Settings action configured on the Advanced page of Add DDNS Profile. This setting can also be controlled using the Enable this DDNS Profile option of the entry’s Add DDNS Profile. Deselecting this option disable the profiles, and no communications with the DDNS provider occurs for this profile until the profile is again enabled.
Online| When selected, this profile is administratively online. The setting can also be controlled using the Use Online Settings option on the entry’s Add DDNS Profile. Deselecting this option while the profile is enabled takes the profile offline, and the network security appliance takes the Offline Settings action that is configured on the Advanced page.
Configure| Includes the Edit icon for configuring the DDNS profile settings and the Delete icon for deleting the DDNS profile entry.

Configuring Dynamic DNS Profiles
For general information on setting up DDNS Profiles, refer to Configuring Dynamic DNS.
Using any Dynamic DNS service begins with settings up an account with the DDNS service provider (or providers) of your choice. It is possible to use multiple providers simultaneously. Refer to the various providers listed in Dynamic DNS providers. The  egistration process normally involves a confirmation email from the provider, with a final acknowledgment performed by visiting a unique URL embedded in the confirmation email.After logging in to the selected provider’s page, you should visit the administrative link (typically add or manage) and create your host entries. This must be performed prior to attempting to use the dynamic DNS client on SonicOS. The NETWORK | DNS > Dynamic DNS page provides the settings for configuring your SonicWall
network security appliance to use your DDNS service.

To configure Dynamic DNS on the SonicWall Security Appliance:

1. Navigate to NETWORK | DNS > Dynamic DNS.

2. Click +Add. The Add DDNS Profile dialog displays.

3. If Enable this DDNS Profile is checked, the profile is administratively enabled, and the network security appliance takes the actions defined in the Online Settings section on the Advanced page. This option is selected by default.

4. If Use Online Settings is checked, the profile is administratively online. This option is selected by default.

5. Enter a name to assign to the DDNS entry in the Profile Name field. This can be any value used to identify the entry in the Dynamic DNS Settings table. The minimum length is one character, and the maximum length is 63 characters.

6. From Provider, select the dynamic DNS provider; these providers are described in Supported DDNS Providers. The default is dyn.com.
   IMPORTANT: You must have created a dynamic service record with the DNS provider you select.
   TIP: Not all options are available for all DNS providers. Also, the Note at the bottom of the page displays whether the DNS provider uses HTTP or HTTPS protocol along with a link to the provider’s website.

7. In the User Name field, enter the username for your DNS-provider account. The minimum length is 1 character, and the maximum length is 63 characters.

8. In the Password field, enter your DNS password. The minimum length is one character, and the maximum length is 31 characters.

9. In the Domain Name field, enter the fully qualified domain name (FQDN) of the host name you registered with the DNS provider. Make sure you provide the same host name and domain as you configured. The minimum length is one character, and the maximum length is 63 characters.

10. Optionally, to assign this DDNS profile to a specific WAN interface, select that WAN interface from Bound to. If you are configuring multiple-WAN load balancing, this option allows you to advertise a predictable IP address to the DDNS service. By default, this is set to ANY, which means the profile is free to use any of the WAN interfaces on the network security appliance.

11. If you selected dyn.com for Provider, go to Step 13.

12. When using dyn.org, select the service type that corresponds to your type of service from Service Type:
    Dynamic| Free Dynamic DNS service. This is the default.
    ---|---
    Custom| Managed primary DNS solution that provides a unified primary/secondary DNS service and a Web-based interface. Supports both dynamic and static IP addresses.
    Static| Free DNS service for static IP addresses.

13. Click Advanced.
    TIP: You can usually leave the default settings on this page.

14. The Online Settings section provides control over what address is registered with the dynamic DNS provider. Choose:
    Let the DDNS provider
    detect the IP Address| The Security Appliance allows the DNS provider to specify the IP address
    NOTE: IPv4 only. This option is selected by default.
    ---|---
    Automatically set IP Address to the Primary WAN Interface IP Address| Causes the Security Appliance to assert its WAN IP address as the registered IP address, overriding auto-detection by the dynamic DNS server. Useful if detection is not working correctly. This option is selected by default.
    NOTE: In IPv6: This option is selected by default.
    Specify IP Address manually| Allows for the IP address to be registered to be manually specified and asserted.

15. The Offline Settings section controls what IP address is registered with the dynamic DNS service provider if the dynamic DNS entry is taken off-line locally (disabled) on the network security appliance. Choose:
    Do nothing| Allows the previously registered address to remain current with the dynamic DNS provider. This option is selected by default.
    ---|---
    Use the Off-line IP address previously
    configured at Provider’s site| If your provider supports manual configuration of Off-Line Settings, you can select this option to use those settings when this profile is taken administratively offline.
    Make Host Unknown| Hides the name of the DDNS service.
    Specify IP Address manually| Allows for the IP address to be registered to be manually specified and asserted.

16. Click Add.

Editing Dynamic DNS Profiles

To edit a DDNS profile:

1. Navigate to NETWORK | DNS > Dynamic DNS.
2. In the Dynamic DNS Profiles table, click the Edit icon of the profile. The Edit DDNS Profile dialog displays.
3. Make changes. For a description of the options, follow the instructions for Configuring Dynamic DNS Profiles.
4. Click Save.

Deleting Dynamic DNS Profiles
You can delete one or all DDNS profiles.
To delete a DDNS profile:

1. Navigate to NETWORK | DNS > Dynamic DNS.
2. Click the Delete icon of the profile to be deleted. A confirmation message displays.
3. Click OK.

To delete all DDNS entries:

1. Navigate to NETWORK | DNS > Dynamic DNS.
2. Select the profiles you want to delete.
3. Click Delete All. A confirmation message displays.
4. Click OK.

Configuring DNS Proxy Settings

About DNS Proxy
An IPv4 interface can do name resolution on an IPv4 Internet, and an IPv6 interface can only do name resolution on an IPv6 Internet through DNS proxy. To allow IPv4 clients to access DNS services in a network with mixed IPv4 and IPv6 interfaces,SonicOS supports DNS proxy.
The DNS proxy feature provides a transparent mechanism that allows devices to proxy hostname resolution requests on behalf of clients. The proxy can use existing DNS cache, which is either statically configured by you or learned dynamically, to respond to the queries directly.
The proxy can redirect the DNS queries selectively to specific DNS servers, according to partial or complete domain specifications. This is useful when VPN tunnels or PPPoE virtual links provide multiple network connectivity, and it is necessary to direct some DNS queries to one network, and other queries to another network.
With DNS Proxy, LAN Subnet devices use the SonicWall network security appliance as the DNS Server and send DNS queries to the network security appliance. The network security appliance proxies the DNS queries to the real DNS Server. In this way, the network security appliance is the central management point for the network DNS traffic, providing the ability to manage the DNS queries of the network at a single point.
NOTE: To maintain security, an incoming DNS Query is proxied only after Access Rule and DPI checking. About the access rule, behavior depends on the device mode:

• On global mode devices:
• Access rules will be auto-added according to the DNS rule configurations.
• On policy mode devices:

Access rules need to be manually added after enabling DNS rules. Navigate to POLICY | Rules and Policies> DNS Rules page to enable DNS rules. For more information about DNS Rules, refer to Rules and Policies guide.

Topics:

• Supported Interfaces
• DNS Server Liveness Detection and Failover
• DNS Cache
• High Availability Stateful Synchronization of DNS Cache

Supported Interfaces
The DNS proxy feature is supported on:

• Physical interfaces
• VLAN interfaces
• VLAN trunk interfaces

The zone for each interface should only be:

• LAN
• DMZ
• WLAN

DNS Server Liveness Detection and Failover

When multiple DNS servers are configured, to determine the “best” server, SonicOS considers these factors:

• DNS server priority
• DNS server status (up, down, unknown)
• Time duration after failover

DNS Cache

In DNS Proxy, a DNS cache memory saves the most commonly used domains and host addresses, and when it receives the DNS query that match the domain in DNS cache, the firewall directly responds to clients by using the cache records, without processing DNS query and reply proxy.
There are two kinds of DNS Cache:

does the deep inspection on the URI and records the valid response to the caches.

When a DNS query matches an existing cache entry, the SonicOS DNS Proxy responds directly with the cached URI. This usually decreases the network traffic and, therefore, improves overall network performance.

Static DNS Cache Size
Static DNS cache entry size is always 256 regardless of platform. The static DNS cache is never be deleted unless it is done manually.
Dynamic DNS Cache Size
Dynamic DNS cache size depends on the platform. Some examples are shown here:

SM 9400
SM 9600| 4096
SM 9200| 2048
NSA 4600
NSA 5600
NSA 6600| 2048
NSA 2600
NSA 3600| 1024
TZ600| 512
TZ300/TZ300W
TZ400/TZ400W
TZ500/TZ500W| 512

If the maximum DNS cache size has been reached when the network security appliance attempts to add an entry to it, the network security appliance will:

1. Delete the DNS cache entry with the earliest expire time.
2. Add the new DNS cache entry.

High Availability Stateful Synchronization of DNS Cache

DNS proxy supports stateful synchronization of DNS cache. When the DNS cache is added, deleted, or updated dynamically, it synchronizes to the idle firewall.
DHCP Server
Configure DNS Proxy on the POLICY | Rules and Policies> DNS Rules page.Navigate to NETWORK System> DHCP Server, you have to manually configure the interface IP as DNS server in DHCP Server Lease Scope tab. Click Add Dynamic.

In the Dynamic Range Configuration dialog, enable Specify manually option and the DNS server IP is added manually into the DNS/WINS page. For more information about configuring the DHCP server, refer to Configuring DNS Settings.

Enabling Log Settings
Several events logs are related to DNS Proxy and need to be configured. For more information refer to SonicOS
7.1 Device log Guide.

Monitoring Packets
The process of DNS Proxy is monitored with MONITOR > Tools & Monitors > Packet Monitor. For information refer to SonicOS 7.1 Monitoring Guide.

Configuring DNS Proxy Settings

Configuring DNS Proxy Settings

To configure DNS Proxy:

1. Navigate to POLICY | Rules and Policies> DNS Rules page to configure DNS Proxy. For more information about DNS Rules, refer to Rules and Policies guide.

2. From the Adding DNS Policy option, to use UDP only or UDP and TCP. Choose the following Service from the Source/Service tab:
   • DNS (Name Service)
   • DNS (Name Service) TCP
   • DNS (Name Service) UDP

3. For DNS over UDP requests only, select Enforce DNS Proxy for All DNS Requests. This option is not selected by default

4. For DNS over UDP requests only, select Enable DNS Proxy Cache. This option is not selected by default.

5. Click Accept.
   To configure Split DNS servers, refer to Configuring Domain-Specific DNS Servers for Split DNS.

Deleting Static DNS Cache Entries

To delete a static DNS cache entry:

1. Navigate to NETWORK | DNS > DNS Proxy.
2. Click the Static DNS Proxy Cache Entries tab.
3. Select Static DNS Cache entry that you want to delete.
4. Click the Delete icon associated with the entry.

To delete two or more static DNS cache entries:

1. Navigate to NETWORK | DNS > DNS Proxy.
2. Click the Static DNS Proxy Cache Entries tab.
3. Select the checkboxes of the entries to be deleted. Delete becomes available.
4. Click Delete or the Delete icon in the Configure column.

To delete all static DNS cache entries:

1. Navigate to NETWORK | DNS > DNS Proxy.
2. Click the Static DNS Proxy Cache Entries tab.
3. Click the top checkbox next to the Domain Name column. All entries are selected.
4. Click Delete.

Viewing DNS Proxy Cache Objects

• Expires in n minutes x seconds (Dynamic DNS)
• Expired (Dynamic DNS)
• Permanent (Static DNS)
Flush| Flush icon for each entry.

Dynamic DNS cache is added automatically during the DNS Proxy process; static DNS cache is added when you configure it. Dynamic DNS cache has a TTL value and can be flushed. Static DNS cache must be deleted (refer to Deleting Static DNS Cache Entries).

Flushing Dynamic DNS Cache Entries

To flush a dynamic DNS cache entry:

1. Navigate to NETWORK | DNS > DNS Proxy.
2. Click the Static DNS Proxy Cache Entries tab.
3. Select the entry you want to flush.
4. Click the Flush icon associated with the entry.

To flush two or more dynamic DNS cache entries:

1. Navigate to NETWORK | DNS > DNS Proxy.
2. Click the Static DNS Proxy Cache Entries tab.
3. Select the checkboxes of the entries to be deleted. Flush becomes available.
4. Click Flush.

To flush all dynamic DNS cache entries:

1. Navigate to NETWORK | DNS > DNS Proxy.
2. Click the Static DNS Proxy Cache Entries tab.
3. Click Flush All.

SonicWall Support

Technical support is available to customers who have purchased SonicWall products with a valid maintenance contract.
The Support Portal provides self-help tools you can use to solve problems quickly and independently, 24 hours a day, 365 days a year. To access the Support Portal, go to https://www.sonicwall.com/support.

The Support Portal enables you to:

• View knowledge base articles and technical documentation
• View and participate in the Community forum discussions at https://community.sonicwall.com/technology-and-support.
• View video tutorials
• Access https://mysonicwall.com
• Learn about SonicWall Professional Services at https://sonicwall.com/pes.
• Review SonicWall Support services and warranty information
• Register for training and certification
• Request technical support or customer service
  To contact SonicWall Support, visit https://www.sonicwall.com/support /contact-support.

About This Document

SonicOS DNS Administration Guide
Updated – December 2023
Software Version – 7.1
232-005873-00 Rev A
Copyright © 2023 SonicWall Inc. All rights reserved.
The information in this document is provided in connection with SonicWall and/or its affiliates’ products. No license, express or implied, by estoppel or otherwise, to any intellectual property right is granted by this document or in connection with the sale of products.
EXCEPT AS SET FORTH IN THE TERMS AND CONDITIONS AS SPECIFIED IN THE LICENSE AGREEMENT FOR THIS PRODUCT, SONICWALL AND/OR ITS AFFILIATES ASSUME NO LIABILITY WHATSOEVER AND DISCLAIMS ANY EXPRESS, IMPLIED OR STATUTORY WARRANTY RELATING TO ITS PRODUCTS INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT. IN NO EVENT  SHALL SONICWALL AND/OR ITS AFFILIATES BE LIABLE FOR ANY DIRECT, INDIRECT, CONSEQUENTIAL, PUNITIVE, SPECIAL OR INCIDENTAL DAMAGES (INCLUDING, WITHOUT LIMITATION, DAMAGES FOR LOSS OF PROFITS, BUSINESS INTERRUPTION OR LOSS OF INFORMATION) ARISING OUT OF THE USE OR INABILITY TO USE THIS DOCUMENT, EVEN IF SONICWALL AND/OR ITS AFFILIATES HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SonicWall and/or its affiliates make no representations or warranties with respect to the accuracy or completeness of the contents of this document and reserves the right to make changes to specifications and product descriptions at any time without notice. and/or its affiliates do not make any commitment to update the information contained in this document.
For more information, visit https://www.sonicwall.com/legal.

End User Product Agreement
To view the SonicWall End User Product Agreement, go to: https://www.sonicwall.com/legal/end-user-product-agreements/.
Open Source Code
SonicWall Inc. is able to provide a machine-readable copy of open source code with restrictive licenses such as GPL, LGPL, AGPL when applicable per license requirements. To obtain a complete machine-readable copy, send your written requests, along with
certified check or money order in the amount of USD 25.00 payable to “SonicWall Inc.”, to:
General Public License Source Code Request
Attn: Jennifer Anderson
1033 McCarthy Blvd
Milpitas, CA 95035

SonicOS 7.1 DNS Administration Guide
SonicWall Support

Documents / Resources

| SONICWALL SonicOS 7.1 DNS Network [pdf] User Guide
SonicOS 7.1 DNS Network, SonicOS 7.1, DNS Network, Network
---|---

References

• changeip.com
• dns.org
• My Dyn Account
• Free Dynamic DNS - Managed DNS - Managed Email - Domain Registration - No-IP
• SonicWall.com
• DNS, Dynamic DNS, VPS and Web Hosting Provider - ChangeIP
• dns.org/
• Free Dynamic DNS - Managed DNS - Managed Email - Domain Registration - No-IP
• SonicWall.com
• SonicWall Community | Technology and Support
• MySonicWall
• sonicwall.com/pes
• MySonicWall
• sonicwall.com/legal
• sonicwall.com/legal/end-user-product-agreements/
• sonicwall.com/support
• sonicwall.com/support/contact-support
• sonicwall.com/support/technical-documentation/
• sonicwall.com/support/technical-documentation/?language=English&category=Firewalls&resources=Administration%20Guide&version=7.1
• sonicwall.com/support/technical-documentation/?language=English&category=Firewalls&resources=Getting%20Started%20Guide
• sonicwall.com/support/technical-documentation/?q=sonicos%20api&language=English
• sonicwall.com/support/technical-documentation/docs/sonicos-7-0-0-1-device_log/Content/introduction.htm/
• sonicwall.com/support/technical-documentation/docs/sonicos-7-0-0-1-tools_and_monitors/Content/z-Front-Matter/tools-and-monitors.htm/
• sonicwall.com/support/technical-documentation/sonicos-7-1-api
• sonicwall.com/support/technical-documentation/sonicos-7-1-monitor

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