PVE Firewall and MTU little trap

bofh

Well-Known Member
Nov 7, 2017
137
17
58
45
I just stumbled across a little nasty trap.

When not setting the firewall check mark in the Network adapter, MTU doesnt seem to be set or taken from the Bridge by default.
However, the Moment you activate the firewall Check mark MTU will be forced set to 1500


This can be a very nasty trap for those of us running smaller MTUs for various reasons. one would be SDN with some QinQ or similar.

Best thing is simply always enter 1 as MTU in a network card where you activate the firewall checkmark. then the Bridge MTU will be used.


and i was wondering why that dam firewall is blocking even tough i deactivated it in the vm option lol....
 

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