iBGP connectivity

[NBenat]

Hello,

I have a three-router topology with all iBGP sessions in the Established state. A PC (10.1.1.100) is attached to R1's G0/0. The 

link between R1 and R2 is also up. Pings from R2 and R3 to 10.1.1.1 (R1 G0/0) are successful but pings from R2 and R3 to the PC are unsuccessful. Any idea why? Thanks in advance.

[MHM Cisco World]

first there is split horizon loop prevent in iBGP 
so R1 must advertise the prefix into R2 and R3 BUT the

next-hop 

is R1, 
R3 never advertise the prefix to R2 even if R2-R1 is link is down, 
what you need is 

run ospf

between the three routers, and then

redistribute BGP into OSPF 

this solve your issue.

[NBenat]

Hi,

Thank you for the reply.
If you take a look at R3's BGP table, you will see that 10.1.1.0 has an
entry for 10.1.1.0 with a best past next hop on R1. I may be mistaken but
doesn't this mean that 10.1.1.0 was advertised to R3? I also stated that
the link between R1 and R2 is up but I forgot to mention that I have full
mesh iBGP configured on these three routers. The PC is also configured with
its default gateway to R1.

[MHM Cisco World · Accepted solution]

ok instead of ping use traceroute, let see when the ICMP is stop from there we will start troubleshooting. 

[NBenat]

I did it before but here are the screenshots. They show and thank you for
your suggestions, that R1 is where it stops. That gave me the idea to try a

redistribute connected

on R1 but that didn't help.

[MHM Cisco World]

in R1 is stop, 
then as @Harold Ritter suggest, 
if you emulate router to be as PC then you need 

ip defualt-gateway 
no ip routing 

[NBenat]

It looks like you both are correct; it doesn't seem to be a BGP problem
after all. I am trying another simulation with the default gateway
command I was using until now for Alpine Desktops on CML. I know that at
some point it was working.

[MHM Cisco World]

usually I use emulate router to be PC, 
and this give me some advance like debug and show L2 counter. 
anyway 
glad your issue is solved. 

[Harold Ritter · Accepted solution]

Hi @NBenat ,

It looks like you might be missing a default gateway setting on the PC. It should be set to 10.1.1.1.

Regards,

[NBenat]

Hello Harold,

Thank you for your reply. The gateway was set and pings fine to the router.

[Harold Ritter]

Hi @NBenat ,

Since R3 could ping R1 (10.1.1.1), but not the PC (10.1.1.100), it looked like the PC might not have a default gateway. What is the PC? Is it possible that it has a host based FW and that is does not allow the ping from R3?

Regards,