--On 10 July 2015 11:06 -0700 John-Mark Gurney <j...@funkthat.com> wrote:

Try bumping the MTU on the root em's by 4 (1504) before creating the
lagg...

I had thought of that - but didn't want to try it (on the basis that out of all the other example config's I've seen - no one else has to, and it will break the lagg MTU).

Anyway I tried it, by:

- Bump the MTU on the em interfaces before creating the lagg to 1504

- The lagg created, inherits this 1504 MTU

That breaks the untagged IP on lagg0 - i.e. I end up with:

"
lagg0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1504

options=4019b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM,TSO4,VLAN_HWTSO>
       ether 68:05:ca:08:1d:3b
       inet x.x.x.x netmask 0xffffff00 broadcast y.y.y.y
"

That MTU of 1504 is going to break lagg0 for untagged traffic :(


- However, the VLAN's setup on the lagg still default to 1496 MTU (despite the underlying interface lagg0 being MTU 1504)

If I 'manually' bump the MTU on the individual lagg0.x VLAN interfaces - they will go to 1500, but traffic is still 'broken'.

I can't 'reduce' the bad MTU on lagg0 either - i.e. 'ifconfig lagg0 mtu 1500' (to try to put it back to 1500) fails with an ioctl error.

So sadly, I'm still stuck :(

Something is lopping 4 bytes off the MTU when it shouldn't need to. None of the example configs I could find were from 10.1-R (or with exactly the same cards) - but obviously this is just bread & butter lagg/VLAN stuff, so it should work?


-Karl
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