Verifying current network MTU sizes

mtu

Hello Network Engineers,

I've been tasked with identifying weather or not my current network has (egress / ingress) MTUs greater than 1400.

My question is, what is the best method of capturing/depicting the network's current MTU sizes and where should I preform this capture/monitor?

This is my first question on the site. I look forward to working with all of you.

v/r

Errdisabled

Best Answer

You can test path MTU discovery across a live network with a tool like tracepath (part of the Linux IPutils package) or mturoute (Windows only). Here's a sample of tracepath output from the lab pictured above, with the MTU of F0/1 reduced to 1400 bytes using the ip mtu command:

Host$ tracepath -n 192.168.1.2
 1:  192.168.0.2       0.097ms pmtu 1500
 1:  192.168.0.1       0.535ms 
 1:  192.168.0.1       0.355ms 
 2:  192.168.0.1       0.430ms pmtu 1400
 2:  192.168.1.2       0.763ms reached
    Resume: pmtu 1400 hops 2 back 254
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