What causes unreachable OSPF neighbor?

[ico]

Hello,

I only want to say I managed to make it work.

I am using OSPF with type nonbroadcast and each "legal" neighbor is 
stated in neighbor list.

In this setup new neighbor started to "work" when I added it to majority 
of neighbors. Previously I tested it with 3 neighbors and those "old 
neighborhood" probably voted my new peer out (sorry for not-so-precise 
terms). When I got majority, everyting started to work as expected.

ico

On 19. 2. 2021 2:27, ico wrote:
> Hello,
> 
> I have 10 routers talking OSPF on a switch on network 10.10.4.0/24. Now 
> I want to add 11th and am unable to make it work. I see the new router 
> in neighbors, also other neighbors on the new router. The new router 
> doesn't get any routes from others, because others see it as unreachable 
> (10.10.4.45 is the new router, 10.10.4.48 is one of old working routers):
> 
>    bird> show ospf topology all
>    ...
>    router 10.10.4.45
>      unreachable
>      network 10.10.4.0/24 metric 10
> 
>    router 10.10.4.48
>      distance 10
>      network 10.8.253.0/26 metric 50
>      network 10.10.4.0/24 metric 10
>    ...
> 
> On the new router - all old routers are unreachable:
> 
>    bird> show ospf topology all
>    ...
>    router 10.10.4.45
>      distance 0
>      network 10.10.4.0/24 metric 10
> 
>    router 10.10.4.48
>      unreachable
>      network 10.8.253.0/26 metric 50
>      network 10.10.4.0/24 metric 10
>    ...
> 
> The normal traffic (ping, ssh) works of course, IP configuration is 
> currently at minimum (single interface, IP 10.10.4.45/24). OS is Linux 
> 5.10, bird 2.0.7.
> 
> Thanks for any help with this.
> 
> ico