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Re: IPv6 next hop routing by static host routes

To: Jürgen Nagler <juergen.nagler@xxxxxxxxxxxxxxxxxx>
Subject: Re: IPv6 next hop routing by static host routes
From: Pekka Savola <pekkas@xxxxxxxxxx>
Date: Mon, 29 Oct 2001 19:05:38 +0200 (EET)
Cc: <netdev@xxxxxxxxxxx>
In-reply-to: <3BDD2001.CFA880EB@xxxxxxxxxxxxxxxxxx>
Sender: owner-netdev@xxxxxxxxxxx
On Mon, 29 Oct 2001, [iso-8859-15] Jürgen Nagler wrote:
> This showed to things:
> 
> 1. the intermediate host is only forwarding if
> /proc/sys/net/ipv6/conf/all/forwarding is set to 1. It isn't enough
> setting .../conf/eth1/forwarding to 1 (with eth1 being the used
> interface for forwarding). You must start setting .../all/forwarding to
> 1, after that it's safe to set 0 for all unused interfaces but vice
> versa setting .../all/forwarding to 0 and setting the only used
> interface to 1 doesn't work. Why not?

Current design is such that all/forwarding is a general setting for 
enabling the forwarding itself, eth0/forwarding etc. just enable 
certain IPv6 features of forwarding (like responding to router 
solicitations).  Please see Documentation/networking/ip-sysctl.txt.
 
> 2. after the first ping6 Echo request/reply pair (node_left pinged
> node_right) the intermediate node sends a redirect for every
> request/reply back to the source saying it should send it the direct
> way. The source ignores the redirect (not sending a new direct packet or
> changing his behavior the next time) and the intermediate node is
> nevertheless forwarding the packet. Is this correct?

When configuring routes:

node_left:
ifconfig eth1 add fec0::202:2dff:fe02:6f3
route -A inet6 add fec0::202:2dff:fe0d:b94a dev eth1
route -A inet6 add fec0::202:2dff:fe05:400c gw fec0::202:2dff:fe0d:b94a
                                               ^^^^

please try using fe80 instead; next-hops should be link-local addresses.


The behaviour you're seeing (that is, not accepting the redirects), could 
be caused by the fact that redirects are sent from the link-local address 
but the next-hop is site-local; these are compared when receiving the 
redirect and they don't match.

Actually one should not accept non - link-local nexthop's (there is a 
comment about that in route.c), and this could be one issue big issue 
caused by that.

-- 
Pekka Savola                 "Tell me of difficulties surmounted,
Netcore Oy                   not those you stumble over and fall"
Systems. Networks. Security.  -- Robert Jordan: A Crown of Swords





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