Tabular display of interface MTUs

When I started exploring the details of MTU handling in Cisco IOS, I quickly got tired of analyzing various long printouts to extract the MTU sizes, so I wrote a Tcl script that display hardware, IP and MPLS MTUs in a tabular format. To install it on your router:

1. Download it from my web site and copy it to your router's flash or NVRAM.
2. Define an alias, for example alias exec mtu tclsh flash:displayMTU.tcl.

The script recognizes two parameters: the ip parameter displays only the interfaces that have IP configured and the mpls parameter displays only the MPLS-enabled interfaces.

Here is a sample printout from one of my lab routers:

R2#mtu
Interface            Hardware     IP   MPLS
=========================================================
FastEthernet0/0          1500          1600
FastEthernet0/1          1500
Serial1/0                1500   1500
Serial1/1                1380   1380   1430
Serial1/2                1500   1500
Serial1/3                1500
Loopback0                1514   1514
Tunnel0                  1514   1476   1476

R2#mtu mpls
Interface            Hardware     IP   MPLS
=========================================================
FastEthernet0/0          1500          1600
Serial1/1                1380   1380   1430
Tunnel0                  1514   1476   1476

You can find more Tclsh-related information in the Tclsh on Cisco IOS tutorial. Sample Tclsh scripts are available in the Tclsh script library. If you need expert help in planning, developing or deploying Tclsh scripts in your network, contact the author.