Exchange Point Lab Exercise 1

Configuring peering with an Upstream and Configuring Local Peering

 

  1. Remove OSPF from your router and do shutdown on your serial links. We will only be using the Ethernet links for this exercise.

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  2. Confirm that you are not longer receiving OSPF routes by doing a show ip route

    3. We will now set up eBGP between all of the routers in the classroom and an upstream router Each table will be its own AS. For example, Table A is AS 1. Table B is AS 2, etc.

     

  3. Figure out your AS number.

    4. AS:

     

    Verify your addressing scheme.

     

  4. We will set up peering sessions according the map. Decide which IP addresses you are going to use for your Point-to-Point Ethernet links with your upstream neighbor.

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  5. Configure BGP on your router to announce your network.

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  6. Set up a peering session with the upstream router.

    7.  

    Router(config)#router bgp 1 //use your AS number

    Router(config-router)#neighbor 133.27.162.112 remote-as 2

    // use the IP address and AS number of your neighbor

    Router(config-router)#neighbor 133.27.162.112 description My-Peer-with-AS2

    Router(config-router)#neighbor 133.27.162.112 update-source loopback0

    Router(config-router)#neighbor 133.27.162.112 prefix-list my-routes out

    Router(config-router)#neighbor 133.27.162.112 prefix-list my-peer in

     

  7. Define the prefix-lists that you will need. This specifies which routes you will send out and which routes you will accept.

    8. Router(config)#ip prefix-list my-routes seq 5 permit 133.27.162.30/29

    Router(config)#ip prefix-list my-routes seq 50 deny 0.0.0.0/0 le 32

    Router(config)#

    Router(config)#ip prefix-list my-peer seq 5 permit 133.27.162.112/29

    Router(config)#ip prefix-list my-peer seq 50 deny 0.0.0.0/0 le 32

    Notice that you will have to confirm with your neighbor as to what routes they are planning

    to send you. In the case above, the neighbor is sending 133.27.162.112/29. Double check

    that you set your "my-routes" outbound filter to contain the network you wish to announce.

    The entries with sequence number 50 are used to deny default routes.

     

     

  8. Check to see if the peering session is up:

    9. Router#show ip bgp sum

    BGP router identifier 133.27.167.252, local AS number 1

    BGP table version is 3, main routing table version 3

    Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd

    133.27.162.112 4 2 0 0 0 0 0 never Idle

     

     

  9. Check to see if you are sending routes to your neighbor? Why or why not?

    10. Router#sh ip bgp neighbor x.x.x.x advertised-routes

     

  10. Check to see if you are receiving routes from your upstream. You should accept "full" routes or default from your upstream.

    11. Router#show ip bgp

    What routes are you receiving?

    Other commands to monitor BGP:

    Router#sh ip route

    Router#sh ip bgp

    Router#sh ip bgp neighbor

    Router#sh ip bgp neighbor x.x.x.x received-routes [*]

    [*] Only works if "soft-reconfiguration inbound" has been configured for this peer

     

  11. Traceroute to all of the other networks in the classroom. Notice the path that they take.

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  12. Set up an exchange point for all of the classroom peers. J Find a hub to use to connect everyone to a shared medium. Use 213.172.133.16/28 as the exchange point address space.

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  13. Gather the necessary information from all of your peers:

    14. AS number of neighbor Prefixes they will be announcing Ip address for peering

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  14. Negotiate peering sessions with all your neighbors (local ISPs). Set these eBGP peering sessions up. Be sure to configure your filters correctly! Only accept customer routes from your peers. Only announce your routes (don’t provide transit!) to your peers.

    15. Note:

    Often, in a BGP speaker, many neighbors are configured with the same update policies (that is, the same outbound route maps, distribute lists, filter lists, update source, and so on). Neighbors with the same update policies can be grouped into peer groups to simplify configuration and, more importantly, to make updating more efficient. When you have many peers, this approach is highly recommended.

    We can use this to simplify our outbound configuration for our peers. We should be announcing just our prefix to our Exchange Point peers:

    For example:

    router bgp 100
 neighbor XP-peers peer-group
 neighbor XP-peers filter-list 99 out
 neighbor XP-peers 
 
 neighbor 171.69.232.90 remote-as 200
 neighbor 171.69.232.90 peer-group XP-peers
 neighbor 171.69.232.90 filter-list 400 in

 neighbor 171.69.232.100 remote-as 300
 neighbor 171.69.232.100 peer-group XP-peers
 neighbor 171.69.232.100 filter-list 401 in

 neighbor 171.69.232.110 remote-as 400
 neighbor 171.69.232.110 peer-group XP-peers
 neighbor 171.69.232.110 filter-list 402 in

     

    Our Inbound prefix lists will vary for each peer as we will only be accepting only our peers’ prefix from each.

     

     

  15. Use a hold-down route for your aggregate for stability

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  16. Traceroute to all of the networks in the class now. What path do you take? Do you see the improvement?