[VLAN] NAT over vlan problem

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> On Wed, Aug 03, 2005 at 06:39:43PM -0400, Jamie ffolliott wrote:
> > All vlan interfaces and eth0 have mtu set to 1480, to deal with
> > oversize ethernet frames from 802.1q's extra 4byte header.
>
> I believe this is the problem.
>
> Try leaving the MTU at 1500 and using the e100 driver, not eepro100.

Yes, that took care of it!

> The e100 driver takes care of the oversized packet problem so no MTU
> compensation is neccessary.

excellent, thanks for the help.

> The fact that small packets come through properly also indicate that
> the problem is MTU related, since the http packets will have the
> maximum allowed size.

I thought mtu related, but local network access simply wouldn't work with
the eepro100 driver and an mtu of 1500, it needed 1496 or less I believe.
Setting back to 1500 worked fine with the e100 driver, and now SNAT also
works.

> Admittedly, when adjusting the MTU down there should be no problem,
> but unless you make the same adjustment on _all_ interfaces on that
> layer 2 network I guess Linux will be unhappy when large packets
> (over 1480 bytes, but under 1500 bytes which is the MTU at the
> sender) arrive, just like when the driver/NIC do not handle this
> properly for packets > 1500 bytes.
>
>
> //Peter
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