Subject: Re: mrouted and gif tunnels
To: None <thorpej@zembu.com>
From: None <itojun@iijlab.net>
List: tech-net
Date: 09/01/2000 15:30:39
>fxp2: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
>        address: 00:d0:b7:88:11:31
>        media: Ethernet autoselect (100baseTX full-duplex)
>        status: active
>        inet 10.0.0.254 netmask 0xffffff00 broadcast 10.0.0.255
>
>gif0: flags=8011<UP,POINTOPOINT,MULTICAST> mtu 1280
>        tunnel inet xx.xx.xx.xx --> xx.xx.xx.xx
>        inet 10.0.0.254 -> 10.0.2.254 netmask 0xffffff00
>
>gif1: flags=8011<UP,POINTOPOINT,MULTICAST> mtu 1280
>        tunnel inet xx.xx.xx.xx --> xx.xx.xx.xx
>        inet 10.0.0.254 -> 10.0.1.254 netmask 0xffffff00
>
>..etc.
>
>Now, when firing up mrouted, I get:
>
>Aug 31 09:53:23 zzz mrouted[1388]: mrouted version 3.8
>Aug 31 09:53:23 zzz mrouted[1388]: warning - ignoring fxp2, same subnet as fxp2
>Aug 31 09:53:23 zzz mrouted[1388]: warning - ignoring gif0, same subnet as fxp2
>Aug 31 09:53:23 zzz mrouted[1388]: warning - ignoring gif1, same subnet as fxp2
>Aug 31 09:53:23 zzz mrouted[1388]: can't forward: only one enabled vif

	another reason for this is, that "netmask" on p2p interface is not
	very meaningful.  we can have couple of interpretation about it,
	and there's no single consensus on it, I believe....

	BSD kernel and gated interpretation: p2p interfaces are /32 (or /128),
		netmask does not really matter
	cisco (and zebra) interpretation: use netmask on p2p interface 
		(but then the question is what if the destionation address
		is outside of the configured prefix?)

	does it help if you set netmask on p2p (gif) to /32?

itojun