BGP network-peer priority

[angelidata]

Hello,

After looking for some days, We have no more ideas how to get following behaviour, so, if someone could help us, we would be really gratefully.

Our scenario is:

 - We have two peers (peerA and peerB)

 - We have two networks (/24) (networkA and networkB)

 - We have BGP sessions with both peers. 

 - peerA has priority against peerB for a specific guest (all traffic are being served by peerA, doesn't matter if it is from networkA or networkB)

How could configure our cisco to be able to do:

   - peerB has more priority when guests visit networkB 

   - peerA has more priority when guests visit networkA

So, we cannot apply    #neighbor X.X.X.X weight    rule because it would affect also networkA and networkB.

We read about local-preferences, weights, metrics,... but it affects all our networks, and only modify priority of external prefixs. Also, peerA and peerB have to announce all networks, networkA and networkB, for redundancy.

How could we configure it? Which is the best way?

Thank you,

[Collin Clark]

If I understand your question correctly, then local-pref will work. When I have two peers, I setup peerA to have preference when accessing peerA networks and preference peerB when accessing peerB networks. If the network is not on peerA or peerB directly, then go out peerA and use peerB as a backup.

Hope it helps.

[angelidata]

Hello Collin,

Maybe I didn't explain it correctly.

My scenario is:

                  GUEST

            /                       \

          /                           \

         |                             |

     peerA                     peerB

         |                              |

           \                           /

              \                      /

                MY ROUTER

In my router I have 2 networks, networkA and networkB

For example a hosting service, if I have a webA on networkA and webB on networkB. 

By default, if GUEST visit webA, data of webA will be sent by best peer (for example peerA), and if GUEST visit webB, data will be sent by peerA again (because it is my best bgp peer for this guest)

What I try to configure is that;

 - if GUEST visit webA, data will be sent by peerA

 - if GUEST visit webB, data will be sent by peerB 

So, same GUEST would receive data of different peer.

If I use local-pref, it means that diferent GUESTS will receive data for diferent peer, but the same guest always will receive data by same peer. Am I wrong? If I am wrong, could you link me an example?

Regards,

[Collin Clark]

You can AS pre-pend networkA to peerB and AS pre-pend networkB on peerA. 

[angelidata]

Hello,

If I am not wrong, prepend only affect traffic in. What we want to decide is traffic out of our router. 

Regards,