BGP route inaccessible

[KiranMalla]

Hi Team, 

I have configured the routers in attached format. I could not able to access the internal networks of R4 router from R1. I could the see the routes advertised in the router but not able to ping.

RTR#1:

Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
10.10.1.2 4 600 103 99 9 0 0 01:34:52 4
192.168.1.2 4 500 100 100 9 0 0 01:34:51 6

Network Next Hop Metric LocPrf Weight Path
*> 172.21.41.0/24 0.0.0.0 0 32768 i
*> 172.21.42.0/24 0.0.0.0 0 32768 i
* i172.21.43.0/24 10.10.2.2 0 100 0 600 i
*> 10.10.1.2 0 0 600 i
* i172.21.44.0/24 10.10.2.2 0 100 0 600 i
*> 10.10.1.2 0 0 600 i
*>i172.21.45.0/24 192.168.1.2 0 100 0 i
*>i172.21.46.0/24 192.168.1.2 0 100 0 i
* i172.21.47.0/24 10.10.2.2 0 100 0 600 i
*> 10.10.1.2 0 600 i
* i172.21.48.0/24 10.10.2.2 0 100 0 600 i
*> 10.10.1.2 0 600 i

Please help me on how to access the networks 172.21.47.0/24 & 172.21.48.0/24 from R1. 

[Georg Pauwen]

Hello,

are you announcing both networks on R4 ? Post the full running config of R4...

[balaji.bandi]

Can you post BGP config also

show ip bgp 

output from all routers ?

[Harold Ritter]

Hi @KiranMalla ,

The issue is that R1 does not know how to reach

next hop 10.10.2.2

On R2, You need to configure

next-hop-self 

towards R1.

router bgp 500

neighbor 192.168.1.1 next-hop-self

Regards,

[KiranMalla]

Hi All, Thanks for your time and replies. Here are the details request. @Harold Ritter I have tried the option but still no luck. I am not sure this is correct design, I have designed for learning and found this issue. R1 is not directly connected to R4 and there is no neighbor-ship to R4. Let me know if any outputs required. 

[Harold Ritter]

Hi @KiranMalla ,

Next-hop-self

is actually not needed towards R4 as it is an ebgp session. My bad.

Regards,

[KiranMalla]

Hi @Harold Ritter , I have issued the command and still not working. 

ASR-JS-02#sh run | sec bgp
router bgp 500
no synchronization
bgp log-neighbor-changes
network 172.21.45.0 mask 255.255.255.0
network 172.21.46.0 mask 255.255.255.0
neighbor 10.10.2.2 remote-as 600
neighbor 10.10.2.2 next-hop-self
neighbor 192.168.1.1 remote-as 500
neighbor 192.168.1.1 next-hop-self
no auto-summary
ASR-JS-02#

[Harold Ritter]

Hi @KiranMalla ,

Can you please let us know exactly what is not working.

Regards,

[KiranMalla]

Hi @Harold Ritter , I am on R1 and trying to ping the loopback interface's configured on R4 i.e., 172.21.47.1 & 172.21.48.1. 

ASR-JS-01#sh ip bgp 172.21.47.1
BGP routing table entry for 172.21.47.0/24, version 11
Paths: (2 available, best #1, table Default-IP-Routing-Table)
Advertised to update-groups:
1
600
10.10.1.2 from 10.10.1.2 (172.21.44.1)
Origin IGP, localpref 100, valid, external, best
600
192.168.1.2 from 192.168.1.2 (172.21.46.1)
Origin IGP, metric 0, localpref 100, valid, internal
ASR-JS-01#
ASR-JS-01#ping 172.21.47.1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.21.47.1, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)
ASR-JS-01#

[Harold Ritter · Accepted solution]

Hi @KiranMalla ,

R4 only knows about R1 loopback interface IP addresses. You nered to souce the ping from 172.21.41.1 or 172.21.42.1 for it to work.

Ping 172.21.47.1 source 172.21.41.1

Regards,

[MHM Cisco World]

Freind you must use

source

in your ping command 

The

source

must be know from the router you ping 

[KiranMalla]

Thank you so much @Harold Ritter  for the clarification. I am able to ping now with the

source

command. Thanks for your time on helping me to understand. 

[Harold Ritter]

You are very welcome @KiranMalla 

[KiranMalla]

Hi @Harold Ritter , One more design I come up. I have deleted the eBGP between R2 & R4 now. and added the next-hop self on R2 to towards R1 and on R4 towards R3. Now I cant ping the networks in R4 from R1 using source. Any idea why it is not able to ping. 

[Harold Ritter · Accepted solution]

Hi @KiranMalla ,

You need to check routes received via iBGP to make sure they are not considered "inaccessible". Since R3 advertises routes received from R1 to R4, you need to have next-hop-self configured there too. 

Regards,