Configuring Default DNS Servers

The device provides default DNS server addresses for IPv4 and IPv6 networks. Each IP address scheme (IPv4 and IPv6) has a primary and a secondary default DNS server. The default IP addresses of these default DNS servers are shown in the following table:

IP Addressing Scheme

Default Primary DNS Server

Default Secondary DNS Server

IPv4

8.8.8.8

8.8.4.4

IPv6

2001:4860:4860::8888

2001:4860:4860::8844

The default DNS servers ensure that applications (for example, Automatic Update feature or pinging a destination) which may need DNS lookups, run seamlessly if you haven't configured any DNS servers in the Internal DNS table and IP Interfaces table. In other words, the device uses the default DNS server as the last resort.

When the device needs to query a DNS server, it selects the DNS server according to the following priority:

■ IPv4 DNS Server:
a. The device queries the DNS server that's configured in the IP Interfaces table for the associated IP Interface (see Configuring IP Network Interfaces).
b. If no DNS server is configured for the associated IP Interface, the device queries the DNS server that's configured for the default IPv4 OAMP IP Interface ("O+M+C").
c. If no DNS server is configured for the default OAMP IP Interface, the device queries the default IPv4 DNS servers (described in this section).
■ IPv6 DNS Server:
a. The device queries the DNS server that's configured in the IP Interfaces table for the associated IP Interface (see Configuring IP Network Interfaces).
b. If no DNS server is configured for the associated IP Interface, the device queries the DNS server that's configured for the default IPv6 OAMP IP Interface ("O+M+C_6").
c. If no DNS server is configured for the default IPv6 OAMP IP Interface, the device queries the DNS server that's configured for the default IPv4 OAMP IP Interface ("O+M+C").
d. If no DNS server is configured for the default IPv4 OAMP IP Interface, the device queries the default IPv6 DNS servers (described in this section).
e. If there are no default IPv6 DNS servers, the device queries the default IPv4 DNS servers (described in this section).

The device uses the default DNS servers only for specific applications such as the SBC Configuration Wizard, CLI ping command, and the Automatic Update feature. The device doesn't use the default DNS servers for call routing.

You can modify the IP addresses of the default DNS servers, as described below.

➢ To modify default DNS server addresses:
1. Open the DNS Settings page (Setup menu > IP Network tab > DNS folder > DNS Settings).

2. For IPv4 DNS servers:
a. In the 'Default Primary DNS Server IP' field, configure the IPv4 address of the default primary DNS server.
b. In the 'Default Secondary DNS Server IP' field, configure the IPv4 address of the default secondary DNS server.
3. For IPv6 DNS servers:
a. In the 'Default Primary DNS Server IPv6' field, configure the IPv6 address of the default primary DNS server.
b. In the 'Default Secondary DNS Server IPv6' field, configure the IPv6 address of the default secondary DNS server.
4. Click Apply.