Re: OSPF NSSA

21 Jan 2023

      W dniu 2023-01-21 01:01, Ondrej Zajicek napisał(a):
...
On Thu, Jan 19, 2023 at 11:45:01PM +0100, Konrad Kręciwilk via 
Bird-users wrote:
...
Hello Team,
Hello
...
but when on the switch remove e.g. vlan4001 to R3 (broken L2 
connectivity),
R1 still see via vlan4001 (all dead times have expired - configured 
bfd).
So even if OSPF neighbor is down/removed, the E1 route is directed to 
the
vlan4001 iface?
...
When I set ifconfig vlan4001 down on R3 the announcement disappears, 
R1 and
R2 to do not see 10.7.100.0/24. if in this state (vlan4001 - broken
connectivity, R3: vlan4001 state down), I restart bird process the 
situation
is getting better - R2 see 10.7.100.254 via vlan4011 and R1 see 
10.7.100.254
via vlan1000 (area0).
If I change export filter to none and add interface vlan91 as stub 
(which has 10.7.100.254) as below:

protocol ospf CORE_OSPF {
         tick 1;
         ipv4 {
                 import all;
                 export none;
         };
         area 0.0.0.1 {
                 nssa;
                 interface "vlan4001" {
                         cost 100;
                         type ptp;
                         bfd yes;
                 };
                 interface "vlan4011" {
                         cost 100;
                         type ptp;
                         bfd yes;
                 };
                 #vlan91 with 10.7.100.254/24
                 interface "vlan91" { stub; };
         };
};

everything works well while stimulating an L2 connection interruption.

I did outputs for you when I had configured translation from NSSA-LSA to 
Ext-LSA:
normale - every vlans works
broken - broken L2 connectivity (vlan4001) from R1 to R3

As you can see show ospf state from R1 has extrenal 10.7.100.0/24 via 
212.127.92.29 (which is local link via vlan4001) which is interrupted 
(L2).
Its look like R3 does not update database (via) when neighbor is lost 
(vlan4001)

area 0.0.0.0

	router 212.127.92.1
		distance 2
		router 212.127.92.2 metric 2
		stubnet 212.127.92.0/30 metric 2
		xnetwork 212.127.92.28/30 metric 110
		xnetwork 212.127.92.128/30 metric 10
		external 10.7.100.0/24 metric 20 via 212.127.92.29

when I do on R3

ifconfig vlan4001 down
ifconfig vlan91 down
ifconfig vlan91 up

database is refreshed and show ospf state looks:

area 0.0.0.0

	router 212.127.92.1
		distance 2
		router 212.127.92.2 metric 2
		stubnet 212.127.92.0/30 metric 2
		xnetwork 212.127.92.128/30 metric 10
		external 10.7.100.0/24 metric 20 via 212.127.92.129 -> it is vlan4011 
from R2 to R3

and 10.7.100.0/24 from R1 is visable via R2 vlan1000 and then via 
vlan4011.

I forget did outputs when I was doing down/up on interfaces.
I you need, I will do.

Regards,
Konrad Kręciwilk
...
That might be a bug in translation from NSSA-LSA to Ext-LSA.
Could you try if some regular prefix on R3 (e.g. stub network on 
another
iface, not external route exported to OSPF) behave correctly, or behave
similarly to the 10.7.100.0/24 prefix?
Could you send 'show ospf state' 'show ospf neighbors' and 'show route'
on R1 / R2 / R3 for each of these steps (initial, after vlan4001 
removal,
after ifconfig, after restart R3)?