Re: another pre-2.0.31 problem

Gestor de Sistemes (
Tue, 10 Jun 1997 11:16:04 +0200 (MET DST)

On 10 Jun, wrote:
> Rogier Wolff <> writes:
>>Nono. This is not a "you can fix it by doing this", but a "because
>>it goes away when I do this, the bug must be THERE".
>>You possibly found the conditions to trigger this bug: masquerading
>>with different MTUs on the different channels. The networking-experts
>>should have a look at trying to reproduce this, and fixing it....
> Exactly. I've caught the PPP driver doing something silly along these
> lines, and I'll be looking over the ISDN stuff as soon as I get enough
> free time. Hopefully within the week. I'd already been suspicious of
> something going wrong in that code, and this pretty much confirms it.

Iīve lived with this bug for the last year with all kernel versions and
ipppd releases.

When the MTUs are different (eth and ippp), 2 things can happen:
-the kernel hangs completely when someone dials in
-not everything is reachable from the masqueraded hosts:
* some web images donīt go through the gateway
* cannot pop mimed mail from an external host

And the last one Iīve discovered is when you choose 1500 as the MTU for
all the interfaces. After a few bytes socket tranmissions stop
completely. For instance listing an FTP directory and starting MC. The
ISDN connection remains, but I have to kill the hang apps.

My final workaround has been setting an MTU of 576. Till now everything
seems to work ok, but I still havenīt tested it enough to be 100% sure.

If you nedd further testing Iīll be pleased to help in anything I can.

Thank you
Pau Aliagas
Ready Soft