Subject: Re: path MTU vs. default route
To: None <>
From: None <>
List: tech-net
Date: 09/27/1999 19:26:09
>I have a machine on a network which is served by two routers, one of which
>is the default route at any given time.  The router selection happens via
>gated and ICMP router discovery protocols.
>The problem is, if I enable PMTU as well, routes to the then-current
>router are added explicitly:
>Destination        Gateway            Flags     Refs     Use    Mtu  Interface
>default       UG         45  2355519      -  fxp0
>     UGHD        3     2119   1450  fxp0
>What I'd like to see is:
>    default            UGHD        3     2119   1450  fxp0
>so when the router changes, the connetion won't get screwed.

	(Assuming your trouble is that cloned route remains installed even when
	default route is changed, not path MTU size issue)

	FreeBSD seems to have kernel code to remove any cloned route, when
	clone parent (default route in this case) gets removed.  This will
	use an extra bit or two in rt_flags.  So, every time the default
	router is changed, cloned route will be removed.
	I'm not sure if this is the way to go or not.