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General • Re: Bridge and VLAN Interface on bridge MTU problem : MTU needs to be L2MTU - 1 ??

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We should be able to put the same MTU as the L2MTU.
Generally setting MTU to a random value is wrong. Generally all devices in same IP subnet (which talk to each other without gateway) should have the same MTU set and unless one knows (much better) industry standard value of 1500 is safe to stick to.

And L2MTU has to be larger than MTU as L2 frame has to hold entire L3 packet (sized up to MTU; L2 equipment don't fragment packets, they drop oversized ones) and its own overhead (for ethernet that's 18 bytes + optional 4 byte VLAN tag). Generally it's safe to have L2MTU much larger than this, but then Tx buffers have to be allocated larger (and less of them fit into available RAM).

So the actual bug here is that ROS allows you to set MTU larger than 1600-18=1582 bytes.

Statistics: Posted by mkx — Sat Feb 17, 2024 9:26 pm



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