This AP has only the one ethernet connector.
Strange, the WRT54GC has a 4-port LAN switch built in...?
If you have a WAP only (e.g. WAP54G), then it will have a single uplink ethernet port to connect to another ethernet network switch. However, this is a Layer 2 connection only, and as such it knows nothing about layer 3 protocols such as TCP/IP where ports are defined.
Perhaps we are talking at cross-purposes here?
SD