Internet Exchange Point Lab Exercise
Configuring BGP Peering with an Upstream and Configuring Local BGP Peering across IXP


1. Remove the entire old configuration from your router with the exception of the interface configurations and user access permissions. We will be using one Serial and two Ethernet links for this exercise.


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

Connect your router's serial port to the upstream router according to the diagram.

We will now set up eBGP between all of the routers in the classroom and the corresponding upstream router.   Each table is its own AS.  For example, Table A is AS 1100.  Table B is AS 2100, etc.  


3. Figure out your AS number.

AS: 


Verify your addressing scheme.

4. We will set up peering sessions according the map.     Contact your upstream provider for the IP addresses you are going to use for your Point-to-Point link.


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


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


Router(config)#router bgp 1100				//use your AS number
Router(config-router)#neighbor 84.201.36.65 remote-as 1
				// use the IP address and AS number of your neighbor

Router(config-router)#neighbor 84.201.36.65 description My-Peer-with-AS1
Router(config-router)#neighbor 84.201.36.65 update-source loopback0
Router(config-router)#neighbor 84.201.36.65 prefix-list my-routes out
Router(config-router)#neighbor 84.201.36.65 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.

Router(config)#ip prefix-list my-routes seq 5 permit 80.201.64.128/28
Router(config)#ip prefix-list my-routes seq 10 deny 0.0.0.0/0 le 32
Router(config)#
Router(config)#ip prefix-list my-upstream seq 5 deny 10.0.0.0/8 le 32
Router(config)#ip prefix-list my-upstream seq 10 deny 127.0.0.0/8 le 32
Router(config)#ip prefix-list my-upstream seq 15 deny 172.16.0.0/12 le 32
Router(config)#ip prefix-list my-upstream seq 20 deny 192.0.2.0/24 le 32
Router(config)#ip prefix-list my-upstream seq 25 deny 192.168.0.0/16 le 32
Router(config)#ip prefix-list my-upstream seq 50 permit 0.0.0.0/0 le 32

	Notice that you will have to confirm with your upstream as to what routes they are planning 
	to send you.  In the case above, the neighbor is sending everything.   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:

Router#show ip bgp sum
BGP router identifier 80.201.64.21, local AS number 100
BGP table version is 3, main routing table version 3

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

84.201.64.65   4   1      0     0      3    0    0    never    Idle  



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

 
   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


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






11.  Set up an exchange point for all of the classroom peers.  :)    Find a switch to use to connect everyone to a shared medium.   Use 84.201.60.0/28 as the exchange point address space.





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

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


























13. 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.

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 description Exchange Point Peers
 ..
 neighbor 84.201.60.3 remote-as 2100
 neighbor 84.201.60.3 peer-group XP-peers
 neighbor 84.201.60.3 filter-list 43 in

 neighbor 80.201.60.5 remote-as 3100
 neighbor 84.201.60.5 peer-group XP-peers
 neighbor 84.201.60.5 filter-list 45 in

 neighbor 84.201.60.7 remote-as 400
 neighbor 84.201.60.7 peer-group XP-peers
 neighbor 84.201.60.7 filter-list 47 in
 ..
ip as-path access-list 99 permit ^$
etc

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



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


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





Configuring BGP Peering with a Route Server at an IXP


16. Remove the BGP configuration used for peers at the IXP from your router with the exception of the configurations for upstream provider. (For those who are privileged to connect...)

17. Flush your BGP sessions by doing a clear ip bgp *

18. Confirm that you are not longer receiving  BGP prefixes from the IX by doing a show ip route.

19. Set up your peering session with the Route Server:

Router BGP 65523
 neighbor 84.201.60.13 remote-as 65523
 neighbor 84.201.36.65 update-source loopback0
 neighbor 84.201.36.65 prefix-list my-routes out
 neighbor 84.201.36.65 prefix-list my-peer in

20. Check how many prefixes the Route Server is sending you using sh ip bgp sum
21. Traceroute to all of the networks in the class now. Did it take the same path as previously? Do you see the reduction in complexity of adding peers to the exchange?

Real Life Internet Exchange Point Scenario
22. Reconfigure the Class Network as indicated in the diagram.
23. Implement the necessary point to point IP addresses for links within your network from your IP address space.
24. As peering sessions with the route reflector and upstream providers come up, what do you notice?