It is possible to specify a non-standard port number for the DNS server in the command-line interface (by default, the Domain Name System uses the standard TCP/UDP port number of 53).
Command syntax:
ip name-server {address[:port]} [{domain} [on {interface}]]
For example, let's change the port number for the DNS server from 53 to 1253:
(config)> ip name-server 77.88.8.88:1253
(config)> system configuration save