Hi folks, can you clarify few questions I have? Please see attached diagram with detailed IP addressing and config.
a) Don't I need to use
router bgp 213
neighbor 18.104.22.168 update-source loopback0
neighbor 22.214.171.124 ebgp-multihop
for all bgp statements since I am establishing
eBGP session? I included 'update-source and ebgp-multihop' commands
and everything works fine too, but I do not
understand how it works even without it?
b) You see that bgp sessions are being established using serial interface IPs. It
could be a better practice if loopback interfaces
were used for bgp sessions, right?
c) Can you explain again why I need to add
"ip route 126.96.36.199 255.255.192.0 Null0" to make my internal router get routes to Primary and
ebgp multihop command is for non directly connected ebgp peer.
Gw router1(bgp)(AS 200)---->Switch(As200)--->router2 bgp(AS 300)
in the above setup while you configure ebgp session b/w router1 to router 2 , if u miss to configure ebgp multihop command , your bgp state will never come to established.
for the directly connected ebgp peer if u use update source as loopback and if u use ebgp multihop command , router will assume that loopback of remote router is in 2 hop.
hi guys, correct me if i am wrong
a) No you don't. In fact generally speaking you use the physical interface addresses with EBGP and loopback addresses with IBGP.
So it will work fine with both physical and loopback addresses as you have discovered.
b) See a).
c) For an EBGP router to advertise a network using the "network" statement there must be a match in the IGP routing table for that route. So you have
network 188.8.131.52 mask 255.255.192.0
there must be a match in the routing table "sh ip route" for the router to advertise this to other EBGP peers.
As you had to add a static route to your config -
ip route 184.108.40.206 255.255.192.0 Null0
it's safe to assume that this route was not in the routing table originally and so it was not adervtised out until you added the static route.