On 10/08/2011 09:24 AM, Eric Dumazet wrote:
> Le samedi 08 octobre 2011 à 14:08 +0400, Michael Tokarev a écrit :
>> > Yesterday I tried to use 802.1Q VLAN tagging with an (oldish)
>> > e100-driven network card, identified by lspci like this:
>> > 
>> >  00:12.0 Ethernet controller: Intel Corporation 82557/8/9/0/1 Ethernet Pro 100 (rev 02)
>> > 
>> > Just to discover that it does not quite work: packets of
>> > size 1497+ bytes gets lost.
>> > 
>> > This appears to be a classical problems in this case -
>> > something forgot to allocate extra 4 bytes for the
>> > packets.
>> > 
>> > There's at least one bugreport from 2008 (!) about this
>> > very issue: http://bugs.centos.org/view.php?id=2719
>> > which is still open.
>> > 
>> > The kernel I tried this on was 2.6.32, I checked git log
>> > for drivers/net/e100.c - there was no changes up to
>> > current version which may be related to this issue.
>> > 
>> > The question: is this a driver problem or hardware? If
>> > it's the driver, can it be fixed? And if it's hardware,
>> > can the driver notify the user somehow - like, by refusing
>> > to enable VLAN (sub)devices maybe?
>> > 
>> > Yesterday it was actually a bit more complicated for me,
>> > since the card in question was used to connect to our
>> > ISP, and they use fixed MAC address per port, so I had
>> > to find another NIC which is a) able to work with VLAN
>> > tags properly, and b) is able to change its mac address.
>> > Lucky I had a VIA RhineIII which does both :)
>> > 
> Since you have two cards (and probably two machines), maybe you could
> try to track if the problem is a bad transmit or a bad receive ?
>
> tcpdump on both machines, and ping -s 2000 from both sides...
>
> e100 driver seems VLAN enabled at a first glance.
Eric is correct, that e100 does support VLANs.

In addition to Eric's suggestion, can you also provide all the output of
lspci -vvv for the network card?