IPV6 connectivity issue

[Alexander Zubkov]

Hi,

I would check first that address used to ping from the outside is really
the same that is configured in prefsrc. I.e. no typos, etc. You could also
use tcpdump to check what IPs are actually in use.

Regards,
Alexander

On Mon, Jan 6, 2025 at 11:17 PM Julien Sansonnens via Bird-users <
bird-users at network.cz> wrote:

> Dear all,
>
> I'm experincing a nasty problem with IPV6 for some time. I'm certainly
> missing something obvious, don't blame me, I'm still learning :)
>
> I'm using bird 2.0.12 under debian 12 as a router. This router (VPS) has a
> working IPV6 connectivity via the VPS provider.
>
> I own an ipv6 prefix in the form 2a06:xxxxxxxxxx/44
> This prefix is correctly exported to the rest of the world, so my network
> is reachable from the outside. I've assigned a /128 address from this range
> to the lo interface, and when I ping from outside, it works.
>
> I now want my router to use the IPs of my own prefix, rather than those
> belonging to my VPS provider. to do this, I set the “krt_prefsrc” parameter
> in bird.
>
> Now here is the issue:
>
> - If bird isn't running, I can ping IPV6 nodes outside my network. Fine.
> The source address belongs to the VPS provider prefix
> - When I run bird using my own IP as source, pinging TO the outside no
> longer works. But pinging FROM the outside still works.
>
> I receive a full IPV6 table from my upstream and the routes are correct.
> So it's (probably ?) not a routing problem. Everything is routed to the
> ipv6 gateway (my BGP neighbor)
>
> The ping also produces no error messages. I just have to cancel it with
> CTRL-C, and it shows 100% lost packets.
>
> I don't know where the packets get lost. I have no firewall configured.
> Could the problem be that my source IP address (which comes from my own
> prefix) is not in the same network as the IPV6 gateway (which comes from
> the VPS provider)?
>
> Thanks for your help
>
> Julien
>
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