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Interesting!

Semi-related problem I dealt with recently: Google Cloud seems to choose a different magic number of 1460 for their VPCs default MTU, which is annoying if you don't know because its different than the default of everything else (such as docker) will cause random packet drops if you do a standard install of those tools.

Took me a few hours to figure this out.

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I recall working on a customer host that I was ssh'd into. If I did an operation that displayed a bunch of text, the session would freeze up. It wouldn't freeze if I only did a bit of text at at time though. On a whim, I tried lowering the MTU, set it to something like 1000 and it worked without freezing on me. Was able to raise it to 1460 (I believe) and still work, but anything beyond that I would get the session lockups on more than a few sceens of data.

Later I researched it, and they were blocking all of ICMP which not only killed ping, but messed with mtu path discovery. Found some information about it on a Cloudflare blog: https://blog.cloudflare.com/path-mtu-discovery-in-practice

They must be encapsulating traffic on the backend.

There is almost certainly so much network virtualization going on your head would spin.

In the world of ethernet jumbo frames, you'd imagine they could encapsulate the traffic yet still support sensible MTU's...

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