show interface history command

Today I want to show a command that was introduced with IOS 15.1T. Using this command will upgrade your troubleshooting capabilities as you can (finally) look back and have some decent historical data on the interface level.

My home lab uses old equipment that is not supported by this IOS version but fortunately enough I had access to a lab router (2800 series) that was loaded with this latest and greatest version.

So here are few notes on the show interface history command:
To begin with, this command allow you to collect utilization history and show it in a (Cisco kind of) graphical representation. If you’re familiar with the show processes cpu history command you know what I’m talking about. Another similarity to the cpu command is the options: last 60 seconds, last 60 minutes and last 72 hours but since it’s an interface command, you get 2 graphs per time frame: Input and Output
The data that you get can be packets per second (pps) or bit per second (bps), both are useful when you try to get some better understanding of what’s going on with your interface.

Check this example (followed by explanation):

Lab65R2# show interface gigabitethernet 1/1 history 60min

3689548755356314774665664876546

10
9    *
8   **  *                  *
7   *#  #*        **       #*
6  *##  ##    #   ## #* ** ##*  *
5  #### #### *#   ## ##### ###* *
4  ######### ##  *#############**
3 ############## ###############*
2 ############## ################
1 ###############################
0….5….1….1….2….2….3….3….4….4….5….5….6
.          0    5   0   5    0    5   0    5   0   5    0

3333333333333333333333333333331
Mlcst 556555555565555555555565535555700000000000000000000000000000
22322111111     121221211211
57149774766867 133175814422022
iDrop 425727636317619265454496840996600000000000000000000000000000
GigabitEthernet1/1 input rate(mbits/sec)  (last 60 minutes)
* = maximum   # = average

As you can see, it’s not so pretty but it does offer some useful troubleshooting information.
I show here one example of Input history for 60 minutes time frame. You can see the number of multicast (Mlcst) packets and drops, both show per minute data. To get the total number you’ll have to work a bit and add up all the numbers, one by one. You can also see the rate per minute in the graph with average (#) and max (*)  points marked.

To summarize, this is not one of those commands that you’ll use on a daily basis but when time comes and you have a problem, it will come handy and might shed some light on traditionally dark corners.