The natural tendency of routing protocols to prefer a more specific route

[samics]

Hi everyone,

in eBGP protocol i have simulate several router when which them present an AS ,

R1....R8 , 

method of prefer a more specific route has been applied and made in R6 20.20.20.0 255.255.255.0 prefix and in R7 20.20.20.128 255.255.255.128 , and when the R1 need to reach the 20.20.20.20/24 server , it still reach R6 Destination Although i put a more specific and longest prefix in R7 with 20.20.20.128 255.255.255.128

help me please.

[balaji.bandi]

Quick Glance 20.20.20.20/24 not part of the subnet right 20.20.20.128 255.255.255.128 ?

Correct me if iam wrong, also good to post show ip bgp route from both R6 and R7 to understand.

[samics]

Only a misspelling occurred , I mean 20.20.20.132 /24 server

thank you

[balaji.bandi]

Can you post the information as requested in the last post ?

[Giuseppe Larosa]

Hello samics,

most specific route should be preferred but only if it is a valid route

post from R1

show ip route 20.20.20.132

and

show ip bgp 20.20.20.0

show ip bgp 20.20.20.128

Either the most specific route is missing for iBGP split horizon rule or if you are using eBGP only the route may have a BGP next-hop that is not validated on R1 in this case this would explain why the most specific route is not considered.

Hope to help

Giuseppe