Gateway on routed network problem (aka: Received route with strange next-hop)

Baptiste Jonglez bjonglez at illyse.org
Thu Sep 4 09:06:13 CEST 2014


If you add the routes with iproute2 on Linux, use the "onlink" flag:

  http://marc.info/?l=bird-users&m=139809577125938&w=2


On Thu, Sep 04, 2014 at 02:16:58AM +0200, Alexander Demenshin wrote:
> Hi,
> 
> I've a static protocol which has routes like:
> 
>   route 10.0.0.0/24 via "uplink";
>   route 192.168.0.0/24 via 10.0.0.1;
> 
> Obviously, this does not work in Bird, though this is perfectly valid and
> accepted by the Linux kernel (as long as "uplink" is up).
> 
> When adding this route manually (ip route), I see in the log file messages
> like:
> 
>   KRT: Received route 192.168.0.0/24 with strange next-hop 10.0.0.1
> 
> I've found why this is so (from
> http://permalink.gmane.org/gmane.network.bird.user/2042):
> 
> "BIRD generally assumes tha that gateway of routes is a direct neighbor
> according to IP addresses on interfaces, not according to routing tables."
> 
> Well, now the question - *why* Bird assumes so and how to remove this
> assumption?
> 
> In my situation, "uplink" is actually ethernet, not any kind of PtP
> interface, and I really want to avoid adding local IP which is in gateway's
> network (in some cases this is simply impossible due to tiny transfer
> networks and multiple gateways).
> 
> Is there any easy fix for this? I feel that only few lines could be changed
> to allow this, but I don't know the code well (yet).
> 
> Thank you!
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