Re: another pre-2.0.31 problem

Clive Messer (
Tue, 10 Jun 1997 21:47:03 +0100 (BST)

On Tue, 10 Jun 1997, Gestor de Sistemes wrote:

> >>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.

Just to add my 2p....

I used to have this problem. I started out with a masq box 'servicing'
12 clients (predominantly NT4.0) using a dial-up modem for our internet
connection. I had to change MTU on ppp0 to 1500 to match that of the
ethernet interface to resolve this issue. Since then I have added a Teles
16.3 card with ippp0 set to MTU 1500 and have not seen the problem.
Interestingly, I dial in from home to the 'old' modem with MTU/MRU=576 and
I dont see the problem. Perhaps I am just lucky?

> 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.

Well, it works great for me with MTU=1500. I dont see any of the problems
you describe above.

> 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.

Well, my setup is well tested. Although our ISDN link is dial-on-demand it
spends most of the working day online. Current uptime = 30 days and I have
seen none of the problems described whilst masquerading 12 hosts via
ethernet and one over the 28k8 dial-up. ippp0 mtu=1500, eth0 mtu=1500, and
ppp0 mtu=576.


C Messer
<>     |   "I pressed her thigh and death smiled."
<>   |    Jim Morrison.