From: Marek Michalkiewicz <[email protected]>
To: Debian Bug Tracking System <[email protected]>
Subject: Bug#85426: default route uses wrong interface with the same IP address

Package: ppp
Version: 2.4.0f-1
Severity: wishlist

The pppd "defaultroute" option, when the ppp0 interface comes up, seems
to do the equivalent of "route add default gw $ip_address", and I think
it should do the equivalent of "route add default dev ppp0" instead.

In most normal cases this shouldn't matter (because each interface has
its own unique IP address), but specifying the interface by name (not
by its IP address) may be preferable if there is more than one interface
with the same IP address.

I have a dummy0 interface with the same IP address as that of ppp0.
This makes it possible to connect to the box from the internal LAN
using its normal hostname (even if ppp0 is down at the moment), and
to run named (possibly started before ppp0 comes up) as non-root.

Using the "defaultroute" option causes pppd to set up the default route
via dummy0 (first device found with matching IP address), not ppp0.
I've worked around this by disabling the pppd defaultroute option and
creating a small shell script called /etc/ppp/ip-up.d/000defaultroute
(run before 00ipmasq) with the following contents:

#! /bin/sh
set -e
/sbin/route add default dev $PPP_IFACE

This gets the default route right (no corresponding ip-down script is
necessary - when ppp0 goes down, the route is removed automatically).
Please consider at least documenting this workaround, as I think it
may be useful to someone.

Thanks,
Marek

-- System Information
Debian Release: testing/unstable
Architecture: i386
Kernel: Linux alf 2.2.19pre7 #1 Sat Jan 27 15:26:41 CET 2001 i586

Versions of packages ppp depends on:
ii libc6 2.2.1-1 GNU C Library: Shared libraries an
ii libpam-modules 0.72-12 Pluggable Authentication Modules f
ii libpam0g 0.72-12 Pluggable Authentication Modules l
ii netbase 4.05 Basic TCP/IP networking system
ii sysvinit 2.78-4 System-V like init.