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List:       freebsd-net
Subject:    Re: ipv6/gif/cisco syslog noise
From:       JINMEI Tatuya / =?ISO-2022-JP?B?GyRCP0BMQEMjOkgbKEI=?= <jinmei () isl ! rdc ! toshiba ! c
Date:       2001-09-25 4:48:21
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Hi,

Thanks for the quick response.

>>>>> On Fri, 21 Sep 2001 11:10:30 -0400, 
>>>>> Joe Abley <jabley@automagic.org> said:

> In this case, on the cisco router which terminates the tunnel, defining
> the tunnel interface with a 126-bit netmask causes a /126 prefix to be
> distributed in the IGP, and this provides reachability information for
> both ends of the tunnel to other routers in the network.

> If the cisco interface had been numbered with a 128-bit netmask, a
> /128 prefix would have been distributed which would have provided
> reachability information for the cisco tunnel interface, but not the
> FreeBSD gif interface. Hence traffic sourced from the FreeBSD box using
> that gif interface address as a source address would not get replies
> routed correctly.

Hmm, then, you might want to try the following configuration:

ifconfig gif0 inet6 2001:438:1fff:ffff:8::32 prefixlen 126

that is, using a prefix length smaller than 128 *without* specifying
the destination address.  I'm not sure if this works well for FreeBSD
4.3, but it surely does at least for FreeBSD 4.4.

Actually, The KAME/BSD kernel does not treat p2p interfaces
differently from (NB)MA interfaces in terms of IPv6 addressing.  In
other words, it should be compatible with commercial routers such as
Cisco and Juniper.

> The reason for allocating four addresses (a 126-bit prefix) to the
> point-to-point link stems from similar practice in IPv4, I think (it
> wasn't my decision; it's current policy in AS6461).

I'd use /64 instead of /126, since there is no reason to save address
space in IPv6, but it is of course up to the site's decision.

					JINMEI, Tatuya
					Communication Platform Lab.
					Corporate R&D Center, Toshiba Corp.
					jinmei@isl.rdc.toshiba.co.jp

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