Subject: Re: Setting SLIP MTU? Using a particular PPP interface?
To: Mason Loring Bliss <>
From: Bill Studenmund <>
List: current-users
Date: 10/06/1997 12:11:52
On Mon, 6 Oct 1997, Mason Loring Bliss wrote:

> 1) Is it possible to set a custom MTU for a SLIP connection without
> recompiling anything? (I don't have the sources for SLIP... Well, I have
> some random SLIP package sources that came with the Red Book, but I'd like
> to stick with NetBSD-standard stuff this time. I'll snag the sources if I
> have to, but I'd like to have the MTU be something other than hardwired
> into the source!) Using the ifconfig "mtu foo" option doesn't work with our
> SLIP, and there doesn't seem to be an appropriate slattach argument.

The mtu setting should work. The problem is that SLIP has a hard upper
limit on packet size. See sys/net/if_sl.c to learn more.

> 2) If I can't manage to get SLIP to use a larger MTU, is there any way I
> can specify that pppd use the ppp1 interface? A perusal of the pppd man
> page didn't enlighten me. What I want is to use ppp0 for my outside
> connection, and ppp1 for my local connection.

Why does it matter which pppd is which? Isn't all the ipnat stuff address

Take care,