Subject: Setting SLIP MTU? Using a particular PPP interface?
To: Current Users <current-users@NetBSD.ORG>
From: Mason Loring Bliss <>
List: current-users
Date: 10/06/1997 09:34:34
Hi, all.

It was just suggested to me that the "need to frag" errors I'm getting
while trying to get some random packets from the outside world (over PPP)
to an IP-NAT-mapped Macintosh (over SLIP) are probably happening because
the MTU between my NetBSD box and my Mac is too small. Sure enough, the MTU
for my SLIP connection is 296.

So, I have two questions:

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.

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.

Thanks in advance for the help!

        Mason Loring Bliss    /\   /()\   awake ? sleep() : dream();
<barbaric>YAWP!</barbaric>  /    \  Squeak to me of love!