VLAN MTU problem in 4.9 ?

[Stephane Raimbault]

Anything specific you want me to do while I'm doing the tcpdump?

I looked at the man page for the vlan after you mentioned it... I'm not sure 
if it applies or not... my MTU is set to 1500 by the system for the 
interfaces and vlan's.  I'm pretty sure when I was running 4.9-RC2 it was as 
well but I'm not 100% sure.

Thanks,
Stephane.


>From: Michael Sierchio <kudzu at tenebras.com>
>To: Stephane Raimbault <segr at hotmail.com>
>CC: net at freebsd.org
>Subject: Re: VLAN MTU problem in 4.9 ?
>Date: Fri, 26 Dec 2003 15:15:03 -0800
>
>Stephane Raimbault wrote:
>
>>So it seems that when I specify a ping of greater then 1468 the pings stop 
>>responding to the vlan interface on the freebsd router?
>>
>>I also did a tcpdump while doing these pings from the freebsd router and 
>>it doesn't see any packets when specifying a ping of 1469, but it sees the 
>>ping with pkt size specified to 1468.
>>
>>Any thoughts on this problem that I'm having?  Any other data I can 
>>provider perhaps?
>
>DF?  Size of tagged frames?  Recall that "packet size" perhaps not
>what you think, also.
>
>Have you read the vlan man page, specifically:
>
>      Note: Unless marked as having native support for vlan, the above 
>drivers
>      don't inform the vlan driver about their long frame handling 
>capability.
>      Just increase the MTU of a vlan interface if it appears to be lower 
>than
>      1500 bytes after attaching to a parent known to support long frames.
>
>But you invite speculation -- a raw tcpdump (-nqvv or so) would
>be nice.
>
>

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