Why i'm unable to ping from ebgp router to ibgp end router?

[Anastk]

I have a small setup in my GNS3 where I am trying to understand some basic iBGP and eBGP concepts.

Please refer to the diagram

R1 >>>

router bgp 100
no synchronization
bgp log-neighbor-changes
network 10.0.0.0 mask 255.255.255.0
neighbor 10.1.1.2 remote-as 200
no auto-summary
router bgp 200
no synchronization
bgp log-neighbor-changes
network 10.0.0.0 mask 255.255.255.0
network 192.168.1.0 mask 255.255.255.252
neighbor 10.1.1.1 remote-as 100
neighbor 192.168.1.2 remote-as 200
no auto-summary

===========================
R2>>>
router ospf 1
router-id 2.2.2.2
log-adjacency-changes
network 2.2.2.0 0.0.0.255 area 0
network 10.1.1.0 0.0.0.255 area 0
network 192.168.1.0 0.0.0.255 area 0
router bgp 200
no synchronization
bgp log-neighbor-changes
network 192.168.1.0 mask 255.255.255.252
network 192.168.2.0 mask 255.255.255.252
neighbor 192.168.1.1 remote-as 200
neighbor 192.168.1.1 route-reflector-client
neighbor 192.168.2.2 remote-as 200
neighbor 192.168.2.2 route-reflector-client
no auto-summary
===========================

R3>>>
router bgp 200
no synchronization
bgp log-neighbor-changes
network 192.168.1.0 mask 255.255.255.252
network 192.168.2.0 mask 255.255.255.252
neighbor 192.168.1.1 remote-as 200
neighbor 192.168.1.1 route-reflector-client
neighbor 192.168.2.2 remote-as 200
neighbor 192.168.2.2 route-reflector-client
no auto-summary

router ospf 1
router-id 3.3.3.3
log-adjacency-changes
network 3.3.3.0 0.0.0.255 area 0
network 192.168.1.0 0.0.0.255 area 0
network 192.168.2.0 0.0.0.255 area 0

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

R4 >>>

router bgp 200
no synchronization
bgp log-neighbor-changes
network 192.0.0.0
neighbor 192.168.2.1 remote-as 200
no auto-summary

router ospf 1
router-id 4.4.4.4
log-adjacency-changes
network 4.4.4.0 0.0.0.255 area 0
network 192.168.2.0 0.0.0.255 area 0

[balaji.bandi]

Why i'm unable to ping from ebgp router ibgp end router? 

what is the source IP address and what is the destination IP address ?

do you see that IP in the routing table ?( where you initiating ping ?)

also, explain with more description what config belongs to what Router ?

[Anastk]

Hi @balaji.bandi 
I have modified the body of my message, Can you have a look now?

i was trying to ping from R1 10.1.1.1 to R4 ipaddress 192.168.2.2 but unsuccessful

Also i tried with bgp redistribute-internal command on R2 ,still no luck

[balaji.bandi]

Thank you for the information, Hope you have resolved the issue with other suggestions. Good stuff.!!

[Georg Pauwen]

Hello,

it is difficult to figure out which configuration belongs to which router. Post the configs with the router names.

Either way, which IP addresses are you trying to ping, and from where (source/destination) ?

Typically, in order to reach iBGP neighbors, you would need the 'bgp redistribute-internal' command (on the R2 router in your case)...

[Anastk]

Hi @Georg Pauwen 
I have modified the body of my message, Can you have a look now?

i was trying to ping from R1 10.1.1.1 to R4 ipaddress 192.168.2.2 but unsuccessful

Also i tried with bgp redistribute-internal command on R2 ,still no luck

[Georg Pauwen · Accepted solution]

Hello,

thanks for the clarification. On R2, add the line marked in bold:

R2>>>
router ospf 1
router-id 2.2.2.2
log-adjacency-changes
network 2.2.2.0 0.0.0.255 area 0
network 10.1.1.0 0.0.0.255 area 0
network 192.168.1.0 0.0.0.255 area 0
router bgp 200
no synchronization
bgp log-neighbor-changes
--> redistribute ospf 1 match internal external 1 external 2
network 192.168.1.0 mask 255.255.255.252
network 192.168.2.0 mask 255.255.255.252
neighbor 192.168.1.1 remote-as 200
neighbor 192.168.1.1 route-reflector-client
neighbor 192.168.2.2 remote-as 200
neighbor 192.168.2.2 route-reflector-client
no auto-summary

[Anastk]

Hi @Georg Pauwen ,

Thank you very much for the above solution/command and it worked!!!

Now i'm able to ping from router 1(Ebgp) to router 4(Ibgp)

Is it possible for you to explain what caused the issue and how this command made it worked?

Do we use this command in real networking environment?

[Georg Pauwen · Accepted solution]

Hello,

basically what this command does is enable BGP to reach all routes that are known to OSPF. Redistribution of routing protocols is often used in 'real' networks...

[Giuseppe Larosa]

Hello @Anastk ,

from the configuration that you have posted in your initial post ( after you have modified it) we can say that communication between 10.1.1.1 and 192.168.2.2 should happen because R2 can advertise prefix 192.168.2.0/30 to R1

R2>>>
router ospf 1
router-id 2.2.2.2
log-adjacency-changes
network 2.2.2.0 0.0.0.255 area 0
network 10.1.1.0 0.0.0.255 area 0
network 192.168.1.0 0.0.0.255 area 0
router bgp 200
no synchronization
bgp log-neighbor-changes
network 192.168.1.0 mask 255.255.255.252
>>>>network 192.168.2.0 mask 255.255.255.252
neighbor 192.168.1.1 remote-as 200
>>>> neighbor 192.168.1.1 route-reflector-client
neighbor 192.168.2.2 remote-as 200
>>> neighbor 192.168.2.2 route-reflector-client
no auto-summary
===========================

Being netwotk 10.1.1.0 in OSPF area 0 you don't need to use next-hop self on R2 towards R3 and R4.

R2 acts as Route Reflector Server for R3 and R4 so no issues for iBGP split horizion rule that was my first guess.

In addition R2 has in router BGP a network command for prefix 192.168.2.0/30

Check on R1:

show ip route 192.168.2.0

the source IP address used by R1 10.1.1.1 should be known on R4 via OSPF

check

on R4:

show ip route 10.1.1.0

A different matter is when R1 uses its internal LAN address as source (10.0.0.0/24)

you should see an OSPF O route in area 0 with cost 3 for 10.1.1.0

In my opinion being R2 a Route Reflector Server there is no need to redistribute BGP in OSPF or OSPF into BGP. bvecause all three routers are speaking botrh OSPF and BGP ( r2,R3,R4)

Post the relevant show commands asked above.

Hope to  help

Giuseppe