Hi,
I just started learning BGP protocol today, i have some confusion, when we using loopback interface to connect other ebgp using different AS, we have to mention three commands to get neighbor up using non-directly connected interface, the two which i highlighted below is mandatory, i try remvoe this cmd no neighbor 2.2.2.2 update-source lo 0, but the neighbor won't down, its still show BGP state = Established
. (R1 and R2 already advertise loop interface via RIP v2), please explain why and how this neighbor up and even i remove no update source cmd.
R1<---->R2
S111#sh run | sec bgp
router bgp 111
no synchronization
bgp log-neighbor-changes
neighbor 2.2.2.2 remote-as 222
neighbor 2.2.2.2 ebgp-multihop 2
no auto-summary
AS222#sh run | sec bgp
router bgp 222
no synchronization
bgp log-neighbor-changes
neighbor 1.1.1.1 remote-as 111
neighbor 1.1.1.1 ebgp-multihop 2
no auto-summary
AS111#sh ip bgp summ
BGP router identifier 192.168.2.1, local AS number 111
BGP table version is 1, main routing table version 1
Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
2.2.2.2 4 222 32 33 1 0 0 00:30:15 0
AS111#sh ip bgp neighbors
BGP neighbor is 2.2.2.2, remote AS 222, external link
BGP version 4, remote router ID 192.168.1.2
BGP state = Established, up for 00:30:24
Last read 00:00:12, last write 00:00:11, hold time is 180, keepalive interval is 60 seconds
Neighbor capabilities:
Route refresh: advertised and received(new)
New ASN Capability: advertised and received
Address family IPv4 Unicast: advertised and received
Message statistics:
InQ depth is 0
OutQ depth is 0
