On the agent side, you only enable the relevant proxy items in the configuration.
For the port forward, you only forward the NetXMS Agent port, i.e. 4700 TCP.
If you are using zoning, you'd set the default SNMP proxy for the zone to that proxy agent and any SNMP polling for nodes in the zone will automatically happen via the Proxy. Otherwise you probably have to set the SNMP proxy on each node individually.
For the port forward, you only forward the NetXMS Agent port, i.e. 4700 TCP.
If you are using zoning, you'd set the default SNMP proxy for the zone to that proxy agent and any SNMP polling for nodes in the zone will automatically happen via the Proxy. Otherwise you probably have to set the SNMP proxy on each node individually.

