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Bgp neighborship question

CATYO
Level 1
Level 1

Hi.

one question.

why  bgp neighborship doesn"t establish when no dynamic routing protocol is enabled?

 

there four router.

A--------B-------C-------D

they all can ping. 

No dynamic routing

static routing only enabled.

 

Configured bgp as 100 with A and D but bgp neighborshi didn"t establish.

am i missing something??

 

11 Replies 11

Jon Marshall
Hall of Fame
Hall of Fame

As long as the IP address of the peer is reachable it should be able to establish a peering.

If this was EBGP you may need to add extra configuration because it expects a direct connection but it is IBGP because A and D are in the same AS so it shouldn't matter.

Can you provide more details ?

Jon

It was ibgp. Config was like 

//A//

router bgp 10

nei 1.1.34.4(D address) remote-as 10

//D//

router bgp 10

nei 1.1.12.1(A address) remote-as 10

 

they can ping each other. But state, stUck in active

Should work as long as they all have routes to each other and it sounds like they do.

Did you try debugging BGP to see what is actually happening ?

Jon

From A side :

R1#ping 1.1.34.4

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 1.1.34.4, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 80/127/164 ms

R1#show ip route


     1.0.0.0/24 is subnetted, 1 subnets
C       1.1.12.0 is directly connected, FastEthernet0/0
S*   0.0.0.0/0 [1/0] via 1.1.12.2
R1#ping 1.1.34.4

 

R1#sh ip bgp summary
BGP router identifier 1.1.12.1, local AS number 10
BGP table version is 1, main routing table version 1

Neighbor        V    AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
1.1.34.4        4    10       0       0        0    0    0 never    Active
 

 

=======================================================

From D side :

R4#sh ip bgp summary
BGP router identifier 1.1.34.4, local AS number 10
BGP table version is 1, main routing table version 1

Neighbor        V    AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
1.1.12.1        4    10       0       0        0    0    0 never    Active
R4#

 

there's no special log. i tested in my GNS3 and i can open 179 both side by using telnet

weird thing is that when i enabled ospf for all of this topology, BGP neighborship was established.  that's why i asked this question. 

/////////////////////////////////////

router ospf 1

net 0.0.0.0 0.0.0.0 a 0

////////////////////////////////////

If you send me your configurations I can lab it up for you and see if I get the same issue.

What might be worth testing first though is to take a copy of all the routing tables then remove the statics and enable OSPF and compare.

It might show you if some routes are actually missing.

Jon

I tested and found out something. 

removed OSPF

A and D, they have default route like 0.0.0.0 0.0.0.0

so i added static route in A /* ip route 1.1.34.4 255.255.255.255 */

after that, BGP established. what's the issue ?? why can't run with default route? is this only GNS3 problem?

 

Well you learn something new every day :-)

Just did a quick search and apparently BGP will not use a default route when trying to establish a peering.

More specifically the BGP peer that initiates the connection cannot use a default route whereas the peer that receives the request can use a default route to reply to the sender.

Didn't know that, or if I did I have forgotten it.

Jon

Thank you : ) you save me : )

Hello

I didn't know that either - I guess I have read about it and not digested that little nugget of information

cheer Jon

res
Paul


Please rate and mark as an accepted solution if you have found any of the information provided useful.
This then could assist others on these forums to find a valuable answer and broadens the community’s global network.

Kind Regards
Paul

Hello

does an extended ping work and if versa?

ping 1.1.34.4 source 1.1.12.1  

also do do you have any acls denying tcp port 179

 

laastly if the peer isnt directly connected you need to use update source command

 

Res

paul

 

 


Please rate and mark as an accepted solution if you have found any of the information provided useful.
This then could assist others on these forums to find a valuable answer and broadens the community’s global network.

Kind Regards
Paul

they can ping with source command and there's no ACL

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