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Date:      Sat, 02 Aug 2003 01:38:21 -0700
From:      Terry Lambert <tlambert2@mindspring.com>
To:        Boris Kovalenko <boris@tagnet.ru>
Cc:        freebsd-current@freebsd.org
Subject:   Re: bge & vlan stranges
Message-ID:  <3F2B787D.D1C4BCAC@mindspring.com>
References:  <3F2A2B17.4020700@tagnet.ru>

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Boris Kovalenko wrote:
>   I have Compaq DL360G2 with Broadcom BCM5701 Gigabit Ethernet and
> FreeBSD 5.1R installed. There are no problems if I use bge as usual
> network card, but when I try to use 802.1Q vlans, I can't receive (only
> receive, sending is ok) packets more then 1456 bytes! What is the
> problem? BGE driver, VLAN driver or my network configuration?

The encapsulation information is subtracted from your available
MTU, so that is correct.

Some cards have a bogus feature that lets you send longer frames
than the normal MTU, but you can't rely on this feature being
interoperable between card vendors, or being supported on all
cards.

I suppose you want to do this because you are trunking a channel
that goes to a border device, and for some reason you have disabled
receipt of all ICMP, instead of only abusable ICMP, and thus you
have broken end-to-end path MTU discovery.

It would be best if you were to simply fix your ICMP.

-- Terry



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