Automatic source routing

[Ole Troan]

Emmanuel,

>>> The problem is really annoying if you want to use autoconfiguration
>>> in a multihoming scenario without the need for an external daemon.
>>> But maybe i missed a sysctl flag or something like that.
>> 
>> Maybe, maybe not. What system are you using to manage your networking - for example, are you on a recent desktop distro using NetworkManager, which behaves badly in this case?
> 
> I'd say "of course" not. ;) Nothing which could have an effect on the network stack. This is a development system (running on debian wheezy) with only base tools.
> 
> The goal is to have a platform which acts has a multihomed router (with forwarding enabled) but automatically configures its addresses and default routers from RAs (accept_ra set to 2). For this test, the forwarding were disabled in order to limit potential side effects. I also tested with different kernels, it seams the linux kernel always behave like this...
> 
> 
>> 
>>> 
>>> Do you confirm the problem ? Does someone knows any automatic (i mean
>>> in-kernel) solution to source route packets through the right
>>> interface ?
>> 
>> What does your ipv6 routing table look like? ("ip -6 route")
> 
> root at debian:~# ip -6 r
> fd01::/64 dev eth1  proto kernel  metric 256  expires 80554sec
> fd02::/64 dev eth2  proto kernel  metric 256  expires 80557sec
> fd08:2::/64 dev eth3  proto kernel  metric 256 
> fe80::/64 dev eth0  proto kernel  metric 256 
> fe80::/64 dev eth1  proto kernel  metric 256 
> fe80::/64 dev eth2  proto kernel  metric 256 
> fe80::/64 dev eth3  proto kernel  metric 256 
> default via fe80::5054:ff:fe00:132 dev eth1  proto ra  metric 1024  expires 25sec
> default via fe80::5054:ff:fe00:142 dev eth2  proto ra  metric 1024  expires 23sec
> 
> As you can see there are the two default routes, received both from the router on eth1 and eth2, and no alternative rule or routing table.

you need source address dependent routing (e.g. http://tools.ietf.org/html/draft-troan-homenet-sadr-01)
I think the latest kernel has SADR working. enable CONFIG_IPV6_SUBTREES.

cheers,
Ole

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