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iBGP network problem, anyone know the solution ?

R1---------------------------------R2-----------------------------------------R3---------------------------------------R4

10.10.10.1 /8 -- 10.10.10.2 /8 -- 172.172.172.2 /16 -- 172.172.172.3 /16 --192.168.1.3 /24 -- 192.168.1.4 /24

R1 in AS 100

R2,R3,R4 in AS 200

R2 and R4 already setup as non-direct neighbor

R1

router bgp 100

nei 10.10.10.2 remote-as 200

net 10.0.0.0

no auto-summary

R2

router bgp 200

no sync

nei 10.10.10.1 remote-as 100

nei 172.172.172.3 remote-as 200

nei 192.168.1.4 remote-as 200

net 10.0.0.0

net 172.172.0.0

no auto-summary

R3

router bgp 200

no sync

nei 172.172.172.2 remote-as 200

nei 192.168.1.4 remote-as 200

net 172.172.0.0

net 192.168.1.0

no auto-summary

R4

router bgp 200

no sync

nei 172.172.172.2 remote-as 200

nei 192.168.1.3 remote-as 200

net 192.168.1.0

no auto-summary

the question is:

routes in R1 show up in R4's BGP table, but why not in R4's routing table ?

but hey...sometime the R1's route appear in R4's routing table

and if we observe the bgp table sometime the route shows as best(>)

and then the best status gone

R4#h ip bgp

BGP table version is 29, local router ID is 192.168.1.4

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal

Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path

*>i10.0.0.0 172.172.172.2 0 100 0 i

*>i172.172.0.0 172.172.172.2 0 100 0 i

* i 192.168.1.3 0 100 0 i

* i192.168.1.0 192.168.1.3 0 100 0 i

*> 0.0.0.0 0 32768 i

R4#sh ip ro

Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP

D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP

i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2

ia - IS-IS inter area, * - candidate default, U - per-user static route

o - ODR, P - periodic downloaded static route

Gateway of last resort is not set

B 172.172.0.0/16 [200/0] via 172.172.172.2, 00:00:56

B 10.0.0.0/8 [200/0] via 172.172.172.2, 00:00:56

C 192.168.1.0/24 is directly connected, Serial0/0

R4#sh ip bgp

BGP table version is 31, local router ID is 192.168.1.4

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal

Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path

* i10.0.0.0 172.172.172.2 0 100 0 i

* i172.172.0.0 172.172.172.2 0 100 0 i

*>i 192.168.1.3 0 100 0 i

* i192.168.1.0 192.168.1.3 0 100 0 i

*> 0.0.0.0 0 32768 i

R4#sh ip ro

Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP

D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP

i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2

ia - IS-IS inter area, * - candidate default, U - per-user static route

o - ODR, P - periodic downloaded static route

Gateway of last resort is not set

B 172.172.0.0/16 [200/0] via 192.168.1.3, 00:00:16

C 192.168.1.0/24 is directly connected, Serial0/0

R4#

is this the normal behaviour ?

3 REPLIES

Re: iBGP network problem, anyone know the solution ?

BGP uses TCP

BGP based on IGP protocols such as EIGRP, OSPF, IS-IS

It's a good practice to use loopback interfaces for iBGP peering.

New Member

Re: iBGP network problem, anyone know the solution ?

thank you, i'll try your suggestion i see what's the result,

but i still want to know the technical reasoning behind this issue.

rgds

Re: iBGP network problem, anyone know the solution ?

Every bgp prefix have next-hop attribute.

For iBGP next-hop attribute must be know from IGP, not from iBGP.

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