Do you mean with THIS module, or even on any module I will try to add ?
Any module: LAN, PPP, Wifi… As I know is .NETMF limit that at same time you can use only one network interface, so you must disconnect one and connect another… If you will write own network drivers, TCP library(sockets) then you can use multiply interfaces.
Yes there is GetAllNetworkInterfaces() but it as I remember allways return one interface.
For example you can’t use at same time:
So Im prety shure you can’t use at same time LAN1&LAN2 except if you will build own “network drivers and TCP stack”. As GUS mentoined you have option to use some networking chip which have TCP/IP stack build into it and this will solve you problems but give you some other limits(like limited sockets)…