Hoi, As a quick followup why I'm asking about versions -- on a Bird2.0.7, I do see the delete-before-insert: root@chgtg0:~# ip -6 monitor route | grep 2001:678:d78::6 # Raise OSPFv3 cost to prefer tf-0-0 *Deleted* 2001:678:d78::6 via fe80::21b:21ff:febd:c718 dev xe0-3.3102.20 proto bird metric 32 pref medium 2001:678:d78::6 via fe80::6eb3:11ff:fe20:e0c4 dev tf0-0 proto bird metric 32 pref medium # Lower OSPFv3 cost to prefer xe0-3.3102.20 again *Deleted* 2001:678:d78::6 via fe80::6eb3:11ff:fe20:e0c4 dev tf0-0 proto bird metric 32 pref medium 2001:678:d78::6 via fe80::21b:21ff:febd:c718 dev xe0-3.3102.20 proto bird metric 32 pref medium groet, Pim On Sat, May 20, 2023 at 10:51 PM Pim van Pelt <pim@ipng.nl> wrote:
Hoi folks,
At Coloclue AS8283, we upgraded from Bird1.6.8 to Bird2.0.12 this week. We use two separate processes, one for IPv4 and one for IPv6 - and 2.0.7 in Debian is missing the ability to select 'accept ipv4' and 'accept ipv6' in BFD, so we installed backports and version 2.0.12).
I am wondering if Bird2 later than 2.0.7 perhaps has an optimization when swapping routes? I would expect a swap to be "delete + add" but I am seeing only "add with new nexthop" appear in Netlink.
Considering the following topology with link names and OSPFv3 costs associated:
dcg-1 bond0.130 ---- bond0.130 eun-2
| 2000 |
enp1s0f3 enp1s0f2
| |
| 10 10 |
| |
enp1s0f3 enp1s0f3
| 1000 |
dcg-2 eno2.3469 ---- eno2.3469 eun-3
If I restart the OSPFv3 protocol, I see that the topology settles in the expected way. What I observed with bird 2.0.12 is that there is a deletion of the currently selected route followed by one addition, when the shortest path reveales (dcg1 - dcg2 - eun3 - eun2, ospf_metric1 is 1020, this is fine):
root@dcg-1:~# birdc -s /run/bird/bird6.ctl restart ospf1
root@dcg-1:~# ip -6 monitor route | grep 2a02:898:0:300::3
Deleted 2a02:898:0:300::3 via fe80::669d:99ff:feb1:31af dev bond0.130 proto bird metric 32 pref medium
2a02:898:0:300::3 via fe80::669d:99ff:feb1:3910 dev enp1s0f3 proto bird metric 32 pref medium
Now I lower the cost of the dcg-1 -- eun-2 link from 2000 to 100, so that it becomes preferred (cost ospf_metric is 120):
root@dcg-1:~# birdc -s /run/bird/bird6.ctl reconfigure ospf1
root@dcg-1:~# ip -6 monitor route | grep 2a02:898:0:300::3
*[[ HERE ]]*
2a02:898:0:300::3 via fe80::669d:99ff:feb1:31af dev bond0.130 proto bird metric 32 pref medium
I would expect this new addition of the installed route on bond0.130 to be *preceded by a deletion* of the previous route from enp1s0f3, but this is not the case (marked in red with [[ HERE ]]).
To anyone's knowledge: *Has this behavior changed between 2.0.7 and 2.0.12 ?*
groet, Pim -- Pim van Pelt <pim@ipng.nl> PBVP1-RIPE - http://www.ipng.nl/
-- Pim van Pelt <pim@ipng.nl> PBVP1-RIPE - http://www.ipng.nl/