The Administration Interface will not start the SNMP master agent on ports other than 161. However, you can manually start the master agent on another port using the following steps
Edit /server_root/plugins/snmp/magt/CONFIG to specify the desired port.
Run the start script as follows:
./start -shell /server_root/plugins/snmp/magt/magt
The master agent will then start on the desired port. However, the user interface will be able to detect that the master agent is running.