RIP and directly connected routes

olivier a oatech7402 at gmail.com
Fri Mar 20 09:05:28 CET 2015


[ due to my misunderstanding of mailing lists, the end of the discussion
went offline. I copy here for other people / traceback ]

Hi, Olivier!

On 2015-03-10 14:46, olivier a wrote:
 I retried with 2 routers inline :

192.168.4.0/24---[R1]---192.168.1.0/24-[BIRD]----192.168.5.0/24

Shouldn't 192.168.1.0/24 be not announced or announced with metric
infinity on the 192.168.1.0/24 network ?

No :-) The network 192.168.1.0/24 is directly connected network to the
[BIRD] router and it knows this route from the bird.conf configuration
('proto static' or 'proto direct'). Split-horizon rule is applied in update
message only for routes that are sending to the router from which the
[BIRD] router was this routes learned.

BIRD routing table :
 -------------------------------------------------------------------
 $ ip -4 route show
 default via 192.168.1.1 dev eth0  proto static
 192.168.1.0/24 [2] dev eth0  proto kernel  scope link  src
192.168.1.240  metric 1
 192.168.4.0/24 [3] via 192.168.1.230 dev eth0  proto bird
 192.168.5.0/24 [4] dev eth1  proto kernel  scope link  src

192.168.5.1  metric 1
 -------------------------------------------------------------------

BIRD announces on the 192.168.5.0/24 network :

0.0.0.0  Metric 1
 192.168.1.0 Metric 1
 192.168.4.0 Metric 2
 192.168.5.0 Metric 1

BIRD announces on the 192.168.1.0/24 network :

0.0.0.0  Metric 1
 192.168.1.0 Metric 1
 192.168.4.0 Metric 16

Here (192.168.4.0 Metric 16) we see a split-horizon usage. Becouse we are
sending a update to 192.168.1.0/24 network from which we learned about the
network 192.168.4.0.

 192.168.5.0 Metric 1

Okay? :-)

Yours Truly,
Pavel
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