WAN interface card(WIC) slots
Two fixed WIC slots are present in 2600 series router except 2691. It has contained 3 WIC slots.
Network Module Expansion Slot( NM) slot
The purpose of this slot for installing the Network module either WAN or LAN
These are build in integrated LAN controllers in Motherboard. There are three types such as Ehternet, Fast Ethernet and Token ring