Input MIB Giant Incrementing

[philclemens1835]

We are having the "input MIB giant" counter increasing on every interface I've looked at recently, and we have matching MTU's on each side.  I came across this while troubleshooting a customer L2VPN recently, and we spent quite a few cycles chasing the MTU settings due to seeing this counter incrementing on the 9K.

Looking inside our network, I see it on our hundred gig links as well, and there are no issues on those links, layer 1 or otherwise.

Is this counter to be ignored, and instead simply rely on the "input error giant" counter?

What does the "input MIB giant" actually mean?

[pigallo · Accepted solution]

Hello,

Input MIB giants are those well formed frames (thus not errored frames) which are bigger than 1518 bytes.

Input error giant instead are those well formed and valid frames that are dropped because they are larger than the configured MRU. The latter indeed is strictly MTU related as indicates an MTU violation. The former has its importance too and it should not be ignored.

Regards