When matching physical interfaces on a router to what we see in the CLI it is important to understand the Cisco slot naming convention. Cisco will number slots,sub slots, and ports right to left, then bottom to top.
Convention is Slot#/Port# or Slot#/Subslot#/Port#
Review available interfaces from the CLI by issuing the command:
show ip interfaces
Built-in interfaces belong to Slot 0. For example, the 2811 router has two built in Fast Ethernet ports. From the CLI they are identified as Fa0/0 and Fa0/1
Say I plug in a serial module WIC-2T into subslot 0. From the CLI they are identified as S0/0/0 and S0/0/1. This shows the WIC-2T module belongs to slot 0, subslot 0, and we have two interfaces available at ports 0 and 1.
To illustrate another slot, slot 1; I plug a network module extension (NME) known as NM-1FE2W. This has one Fast Ethernet interface and provides two additional subslot spots for wide interface card (WIC) modules above. In my following illustration you can see I have added another WIC-2T to the NM-1FE2W.
As a result I now have two more serial interfaces that are identified in the CLI as S1/0/0 and S1/0/1.
At last I will populate subslot1 of the previously installed NM-1FE2W with a 4 port switch interface card, the HWIC-4ESW. From the CLI you’ll observe 4 new interfaces, Fa1/1/0, Fa1/1/1, Fa1/1/2, and Fa1/1/3.
After adding the NME and all WICs you have access to the following interfaces:
Router>show ip interface FastEthernet0/0 is administratively down, line protocol is down (disabled) Internet protocol processing disabled FastEthernet0/1 is administratively down, line protocol is down (disabled) Internet protocol processing disabled Serial0/0/0 is administratively down, line protocol is down (disabled) Internet protocol processing disabled Serial0/0/1 is administratively down, line protocol is down (disabled) Internet protocol processing disabled FastEthernet1/0 is administratively down, line protocol is down (disabled) Internet protocol processing disabled Serial1/0/0 is administratively down, line protocol is down (disabled) Internet protocol processing disabled Serial1/0/1 is administratively down, line protocol is down (disabled) Internet protocol processing disabled FastEthernet1/1/0 is up, line protocol is down Internet protocol processing disabled FastEthernet1/1/1 is up, line protocol is down Internet protocol processing disabled FastEthernet1/1/2 is up, line protocol is down Internet protocol processing disabled FastEthernet1/1/3 is up, line protocol is down Internet protocol processing disabled Vlan1 is administratively down, line protocol is down Internet protocol processing disabled
Below is a screen shot of what my Cisco 2811 router looks like in Packet Tracer.
