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show ip bgp sum - IBGP still active

Posted on 2016-08-04
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Last Modified: 2016-08-06
Router 1

router bgp 65555
 no synchronization
 bgp log-neighbor-changes
 network 10.12.24.0 mask 255.255.252.0
 network 10.12.24.18 mask 255.255.255.255
 network 172.30.201.14 mask 255.255.255.255
 network 172.30.204.52 mask 255.255.255.252
 neighbor 10.12.24.19 remote-as 65555
 neighbor 10.12.24.19 description IBGP Peer
 neighbor 172.30.204.54 remote-as 1863
 neighbor 172.30.204.54 description ATT
 no auto-summary


Router 2
router bgp 65555
 no synchronization
 bgp log-neighbor-changes
 network 10.12.24.0 mask 255.255.252.0
 network 10.12.24.19 mask 255.255.255.255
 network 172.19.100.14 mask 255.255.255.255
 network 172.19.101.52 mask 255.255.255.252
 neighbor 10.12.24.18 remote-as 65555
 neighbor 10.12.24.18 description IBGP Peer
 neighbor 172.19.101.54 remote-as 1632
 neighbor 172.19.101.54 description VERIZON
 no auto-summary


Router 1
Neighbor        V    AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
10.12.24.19     4 65555 0       0        0    0    0 never    Active

Router 2
Neighbor        V    AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
10.12.24.18     4 65555 0       0        0    0    0 never    Active


I can reach both .18 and .19 from both sides.  Why is this still stuck in active?  iBGP peering was on a different G0/0 interface, but then I created a new one  (neighbor 10.12.24.18 remote-as 65555 and  neighbor 10.12.24.19 remote-as 65555) on a G0/1.  Do I need to do a clear ip bgp so it can reform the iBGP relationship?
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Question by:PeraHoman
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LVL 29

Expert Comment

by:Predrag Jovic
ID: 41743719
Strange ASN number (typically ASN < 65535). :)
Your devices did not sent any messages that is obviously problem (not trying to establish bgp session).
Try to debug if it is lab, I guess your tcp session has problem, something like
BGP: 10.12.24.19 open active, local address 10.12.24.18
BGP: 10.12.24.19 open failed: Connection refused by remote host, open active delayed 31024ms (35000ms max, 28% jitter)
Until TCP session is not OK devices will not send message to try to create bgp session.
You can try to clear bgp session.
In GNS3 typically you need to stop devices and start it again.
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Author Comment

by:PeraHoman
ID: 41744306
I changed the numbers.  The issue was that I peered it to the loopback of each router. I changed to peering to be on the physical interface. Why doesn't it work when I peer to the loopback?  Do I need to add the update source command?
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Accepted Solution

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Predrag Jovic earned 500 total points
ID: 41744332
For peering with loopback you need to use loopback as source, by default interface closest to destination is chosen.
neighbor 10.12.24.18 update-source lo0
 
For iBGP if you use loopback you need to change next hop to router that is sending packets (for iBGP it is not changed by default).
neighbor 10.12.24.18 next-hop-self
Route to destination must be known (static or dynamic). Did you create routes to loopback interfaces?

For EBGP you need to permit multihop (TTL by default is 1 - it is loop prevention mechanism).
neighbor 172.19.101.54 update-source lo0
neighbor 172.19.101.54 ebgp-multihop X
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Author Comment

by:PeraHoman
ID: 41744335
Routes to the Lo0 interfaces are on the routing table on both routers.  I didn't add next-hop or update-source lo0, that's probably why?
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LVL 29

Expert Comment

by:Predrag Jovic
ID: 41744356
By default next hop is not changed while it is propagated in IBGP, in this specific case I would have to check :) , since it is internal network, but for external networks it is a must.
If you are peering with loopbacks you must specify it, otherwise it will not work, wrong address will be used for peering and it is wrong neighbor... link will not be established.
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