Cisco Interfaces In Use

Jan 2024

Introduction

A really useful task to perform when looking at remote systems is to see what interfaces on a Cisco Switch are in use (as in connected).

Interface Status

Lets look at how to see what interfaces we are using: sh interfaces status This has to be performed from the top level, same part of the Cisco menu you would do sh vlan br for instance.

sh interfaces status
Port Name Status Vlan Duplex Speed Type
Gi0/1 connected 2 a-full a-1000 10/100/1000BaseTX
Gi0/2 notconnect 2 auto auto 10/100/1000BaseTX
Gi0/3 notconnect 2 auto auto 10/100/1000BaseTX
Gi0/4 notconnect 2 auto auto 10/100/1000BaseTX
Gi0/5 connected 2 a-full a-1000 10/100/1000BaseTX
Gi0/6 connected 2 a-full a-1000 10/100/1000BaseTX
Gi0/7 connected 2 a-full a-1000 10/100/1000BaseTX
Gi0/8 connected 2 a-full a-1000 10/100/1000BaseTX
Gi0/9 notconnect 2 auto auto 10/100/1000BaseTX
Gi0/10 notconnect 2 auto auto 10/100/1000BaseTX
Gi0/11 notconnect 2 auto auto 10/100/1000BaseTX
Gi0/12 notconnect 2 auto auto 10/100/1000BaseTX
Gi0/13 notconnect 2 auto auto 10/100/1000BaseTX
Gi0/14 notconnect 2 auto auto 10/100/1000BaseTX
Gi0/15 notconnect 2 auto auto 10/100/1000BaseTX
Gi0/16 notconnect 2 auto auto 10/100/1000BaseTX
Gi0/17 notconnect 2 auto auto 10/100/1000BaseTX
Gi0/18 notconnect 2 auto auto 10/100/1000BaseTX
Gi0/19 notconnect 2 auto auto 10/100/1000BaseTX
Gi0/20 notconnect 2 auto auto 10/100/1000BaseTX
Gi0/21 notconnect 2 auto auto 10/100/1000BaseTX
Gi0/22 notconnect 2 auto auto 10/100/1000BaseTX
Gi0/23 notconnect 2 auto auto 10/100/1000BaseTX
Gi0/24 notconnect 2 auto auto 10/100/1000BaseTX
Gi0/25 notconnect 2 auto auto 10/100/1000BaseTX
Gi0/26 notconnect 2 auto auto 10/100/1000BaseTX
Gi0/27 notconnect 2 auto auto 10/100/1000BaseTX
Gi0/28 notconnect 2 auto auto 10/100/1000BaseTX
Gi0/29 notconnect 2 auto auto 10/100/1000BaseTX
Gi0/30 notconnect 2 auto auto 10/100/1000BaseTX
Gi0/31 notconnect 2 auto auto 10/100/1000BaseTX
Gi0/32 notconnect 2 auto auto 10/100/1000BaseTX
Gi0/33 connected 3 a-full a-1000 10/100/1000BaseTX
Gi0/34 connected 3 a-full a-1000 10/100/1000BaseTX
Gi0/35 notconnect 3 auto auto 10/100/1000BaseTX
Gi0/36 notconnect 3 auto auto 10/100/1000BaseTX
Gi0/37 notconnect 3 auto auto 10/100/1000BaseTX
Gi0/38 notconnect 3 auto auto 10/100/1000BaseTX
Gi0/39 notconnect 3 auto auto 10/100/1000BaseTX
Gi0/40 notconnect 3 auto auto 10/100/1000BaseTX
Gi0/41 notconnect 3 auto auto 10/100/1000BaseTX
Gi0/42 notconnect 3 auto auto 10/100/1000BaseTX
Gi0/43 notconnect 3 auto auto 10/100/1000BaseTX
Gi0/44 notconnect 3 auto auto 10/100/1000BaseTX
Gi0/45 connected 1 a-full a-1000 10/100/1000BaseTX
Gi0/46 connected 1 a-full a-1000 10/100/1000BaseTX
Gi0/47 notconnect 1 auto auto Not Present
Gi0/48 notconnect 1 auto auto Not Present

In the above example above we can see that there are 9 interfaces in use, and we can see the following information for each interface:

Port Name Status Vlan Duplex Speed Type
Gi0/1 connected 2 a-full a-1000 10/100/1000BaseTX

The following is what each field means:

Port - This is the interface number on the switch
Name - This only shows if any names have been assigned, generally they are not.
Status - Connected.
VLAN - What VLAN the interfaces is currently in.
DUPLEX - a-full (automatic-full)
SPEED - a-1000 (auto 1000)
TYPE - 10/100/1000BaseTX (this interface supports 10Mb/s / 100Mbs and 1GBs)

Show the Mac Address Table

We can use the following to show what MAC Addresses are present on each interface. If you have an interface that is connected to another switch then you will see all MAC addresses from that switch interface.

sh mac address-table
Vlan Mac Address Type Ports
---- ----------- -------- -----
All 0100.0ccc.cccc STATIC CPU
All 0100.0ccc.cccd STATIC CPU
All 0180.c200.0000 STATIC CPU
All 0180.c200.0001 STATIC CPU
All 0180.c200.0002 STATIC CPU
All 0180.c200.0003 STATIC CPU
All 0180.c200.0004 STATIC CPU
All 0180.c200.0005 STATIC CPU
All 0180.c200.0006 STATIC CPU
All 0180.c200.0007 STATIC CPU
All 0180.c200.0008 STATIC CPU
All 0180.c200.0009 STATIC CPU
All 0180.c200.000a STATIC CPU
All 0180.c200.000b STATIC CPU
All 0180.c200.000c STATIC CPU
All 0180.c200.000d STATIC CPU
All 0180.c200.000e STATIC CPU
All 0180.c200.000f STATIC CPU
All 0180.c200.0010 STATIC CPU
All ffff.ffff.ffff STATIC CPU
2 0025.b4bc.2901 DYNAMIC Gi0/1
2 74fe.4857.6d4a DYNAMIC Gi0/7
2 74fe.4857.72a5 DYNAMIC Gi0/8
2 a4bf.0169.b7af DYNAMIC Gi0/5
2 a4bf.016a.d0eb DYNAMIC Gi0/6
3 74fe.4857.6d4c DYNAMIC Gi0/33
3 74fe.4857.72a7 DYNAMIC Gi0/34
1 74fe.4828.799d DYNAMIC Gi0/45
1 74fe.4828.c136 DYNAMIC Gi0/45
1 9418.8266.b82c DYNAMIC Gi0/45
1 9418.8266.b82d DYNAMIC Gi0/45
1 a4bf.0169.b7ad DYNAMIC Gi0/45
1 a4bf.016a.d0e9 DYNAMIC Gi0/45

I want to look at this specific interface:

Vlan Mac Address Type Ports
2 a4bf.0169.b7af DYNAMIC Gi0/5