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 From:  "Aaron Cherman" <aaronc at morad dot ab dot ca>
 Cc:  <m0n0wall at lists dot m0n0 dot ch>
 Subject:  Re: [m0n0wall] MTU Trouble in FreeBSD 6
 Date:  Sun, 24 Dec 2006 13:44:01 -0700
> On 22.12.06 09:17 -0700, Aaron Cherman wrote:
>
>> kernel: em0: discard oversize frame (ether type 8100 flags 3 len
>> 1518 > max 1418)
>
> I'd try to do without setting any specific MTU (FreeBSD will take the
> extra 4 bytes for the VLAN tag into account automatically) and
> finding the real cause for your MTU problems with VLAN-tagged frames
> - e.g. switches or NICs that don't handle them properly (usually not
> an issue with Intel NICs) - your MTU setting most likely only makes
> things worse. Explicitly setting an MTU below 1500 and/or using MSS
> clamping should only ever be necessary for people who use PPPoE or
> some sort of IP-based tunnel (e.g. GRE) to access the Internet.

An update on this.  I changed my config to remove the MTU settings manually 
entered and did some testing.  All seemed fine and I decided to go live with 
the new config on Friday night.  I rebooted with the newly built CF card 
(1.3b1 and new config) and all is running great.  All VLANs are acting 
normally and no issue to note.  It appears to me that FreeBSD 6 handles the 
VLAN tags a little better.  Yippee!!  Both cascaded m0n0s are running 1.3b1 
now - we'll see if another lock-up occurs any time soon.....

Thanks to Chris and Manuel for the help getting me going.  Much appreciated 
guys.

Merry Christmas...


Aaron