If you need to send syslog messages to a remote server that is not listening on the standard ports, you can specify the port on the input string for syslog server in the CLI or GUI.

From the GUI, navigate to Auditing-->Destinations-->Syslog, then enter IPV4 address followed by a colon ':', for IPV6, enter the IPV6 address with surrounding brackets, then followed by a colon ':', then the custom port number after the colon ':'.

Example from the GUI:

Example from the CLI:

cd /settings/auditing/destinations/syslog

set ipv4_remote_server=yes ipv4_address=192.168.10.50:3491

set ipv6_remote_server=yes ipv6_address=[1fff:0:a88:85a3::ac1f]:3491