bgp rib

[s4sandyad]

i am learning advance bgp : having query

Bgp stores its database in adj-rib-in, local rib (bgp table) and adj-rib-out...

1. but is there any command to show the output of it separately... how can i come to know what is in adj-rib-in or rib-out table ??

2. what is the meaning of sh ip bgp rib-failure command then ??

3. show ip bgp nei advertised routes is equal to adj-rib-out ??

similarly show ip bgp nei recevid routes is equal to adj-rib-in ?

Please help me ...

[Nikhil Kapoor]

Hello s4sandyad, 

Your understanding is correct. Please find below answer to your queries it may help. 

BGP RIB-In stores BGP routing information received from different peers. The stored information is used as an input to BGP decision process. In other words this is the information received from peers before applying any attribute modifications or route filtering to them.

The Adj-RIBs-out: This one stores the routing information that was selected by the local BGP router to advertise to its peers through BGP update messages. Do not forget;  BGP only advertises best routes if they are allowed by local outbound policies.

- what is the meaning of sh ip bgp rib-failure command then ??

When BGP tries to install the bestpath prefix into Routing Information Base (RIB) (for example, the IP Routing table), RIB might reject the BGP route due to any of these reasons:

Route with better administrative distance already present in IGP. For example, if a static route already exists in IP Routing table.

Memory failure.

The number of routes in VPN routing/forwarding (VRF) exceeds the route-limit configured under the VRF instance.

- show ip bgp nei advertised routes is equal to adj-rib-out ??

Yes

- show ip bgp nei recevid routes is equal to adj-rib-in ?

Yes

HTH

Nikhil 

[s4sandyad]

Nikhil Thanks...

means..Router receives updates...these unprocessed routes are stored in adj-rib-in....then it apply incoming policies on it...after process these are stored in local rib table i.e bgp table...is it right??

menas "show ip bgp nei received routes" shows unprocessed routes which r in rib-in or filtered routes which are in local rib.... ???

similarly what about advertised routes???

Please clear me...

[Nikhil Kapoor]

Hello s4sandyad 

- Router receives updates...these unprocessed routes are stored in adj-rib-in....then it apply incoming policies on it...after process these are stored in local rib table i.e bgp table...is it right??

Yes you are correct. 

- Show ip bgp nei received routes" shows unprocessed routes which r in rib-in. In other words this is the information received from peers before applying any attribute modifications or route filtering to them.
The Local RIB The local routing information base stores the resulted information from processing the RIBs-In database’s information. These are the routes that are used locally after applying BGP policies and decision process.

- Similarly what about advertised routes?

his one stores the routing information that was selected by the local BGP router to advertise to its peers through BGP update messages. Do not forget;  BGP only advertises best routes if they are allowed by local outbound policies.

HTH,
Nikhil 

[s4sandyad]

Hi Nikhil...

nice explanation ...thnx..

unlike show ip bgp nei received routes; Show ip bgp nei advertised routes: shows filtered routes after applying outgoing policy... is it ??

[Nikhil Kapoor]

Hi s4sandyad, 

unlike show ip bgp nei received routes; Show ip bgp nei advertised routes: shows filtered routes after applying outgoing policy... is it ??

Yes

HTH,

Nikhil 

[milan.kulik]

Hi, I'd not 100% say "... after applying outgoing policy." here. If you use an outgoing route-map setting BGP attributes like MED or AS prepending, e.g., those attributes are not shown modified by the "sh ip bgp nei advertised" command. Best regards, Milan