basic question bgp/static

[ahmedsid432135621]

hi guys,. a very basic question, i just need some insight in to what is happening here. 10.128.192.1/18 is known to R2 via a static route and bgp is advertising this network on R2. my problem is with the last picture. why is R3 not showing it as a route when i do show ip route 10.128.192.0. it only shows the /24 by default unless i specify /18 although it is learning both as can be seen.

[Georg Pauwen]

Hello,

not really sure what you are asking. Are you trying to display all routes that match the specified prefix ?

Try:

show ip route 10.128.192/0 255.255.192.0 longer-prefixes

[MHM Cisco World]

both is easy since there is Lo in R2 and you config redistribute connected, so it advertise the Lo and static route. 
why /18 because the BGP not advertise prefix if it not same as appear in routing table.

[ahmedsid432135621]

what i mean is, i cant understand the logic behind the display. why doesnt it display both networks, is it because of the longest prefix match? the 18 network is advertised by R2 specifically configured.

[MHM Cisco World]

But i see both in one photo you share.

One is lo and other of static route.

Lo with /24

Static route /18

[Georg Pauwen]

Hello,

do you have the full configs of all three routers so we can lab this up ?

[Harold Ritter · Accepted solution]

Hi @ahmedsid432135621 ,

This is normal behavior in IOS. When you do a

"show ip route <prefix>" 

it will show you only the most specific prefix, as you do not specify a prefix length. If you want to see all prefixes, you need to do

"show ip route 10.128.192.0 255.255.192.0 longer-prefixes" or "show ip route 10.128.0.0 255.255.0.0 longer-prefixes",

as suggested by @Georg Pauwen . This command will show all the received prefixes matching the "prefix/prefix length" specified and the more specific prefixes.

Regards,

[MHM Cisco World]

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