iBGP - Simple static route exchange

[Ondrej Zajicek]

On Thu, Feb 23, 2017 at 04:42:50PM +0100, Cedric Lemarchand wrote:
> Yes, I am not sure to understand how plays theses options (and if I need it) in the bgp protocol and it they are related to my problem :
> 


> gateway recursive : means that if host2 advertise "route 192.168.2.0/24
> via 10.10.2.1;” to host1, host1 does a lookup in the kernel routing table
> and set the nexthop for 192.168.2.0/24 via the same IP as for host2 ?

Mainly yes, but:

1) Not lookup in the kernel routing table, but in the BIRD table. By
default the same table as used by BGP protocol, but could be configured
to different one by 'igp table' option.

2) It is not lookup for host2, but lookup for bgp_next_hop attribute, as
specified by host2, which is usually value of 'via'.

> next hop self : means that every route advertised by host2 will be routed to it self while keeping the “gateway recursive” logic ?

That means host2 always announces own IP address as bgp_next_hop instead
of one from 'via'.

> The output of show route all :

There are two issues:

1) both hosts announce all routes (not only 192.168.xx but also 10.10.xx).

2) routes from kernel1 protocol has lower preference (10), so routes
from BGP are preferred and you get circular lookups for 10.0.1.1, 10.10.2.1

You could change preference of kernel protocol to say 200 and you
could filter out unwanted routes in BGP export filter.

-- 
Elen sila lumenn' omentielvo

Ondrej 'Santiago' Zajicek (email: santiago at crfreenet.org)
OpenPGP encrypted e-mails preferred (KeyID 0x11DEADC3, wwwkeys.pgp.net)
"To err is human -- to blame it on a computer is even more so."
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 181 bytes
Desc: Digital signature
URL: <http://trubka.network.cz/pipermail/bird-users/attachments/20170223/026e25fd/attachment.asc>