Exchange Point Lab Exercise
Configuring peering with an Upstream and Configuring Local Peering across IXP
Connect your routerís 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 100. Table B is AS 1100, etc.
Verify your addressing scheme.
Router(config)#router bgp 100 //use your AS number
Router(config-router)#neighbor 184.108.40.206 remote-as 1
// use the IP address and AS number of your neighbor
Router(config-router)#neighbor 220.127.116.11 description My-Peer-with-AS1
Router(config-router)#neighbor 18.104.22.168 update-source loopback0
Router(config-router)#neighbor 22.214.171.124 prefix-list my-routes out
Router(config-router)#neighbor 126.96.36.199 prefix-list my-peer in
Router(config)#ip prefix-list my-routes seq 5 permit 188.8.131.52/28
Router(config)#ip prefix-list my-routes seq 10 deny 0.0.0.0/0 le 32
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.
Router#show ip bgp sum
BGP router identifier 184.108.40.206, 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
220.127.116.11 4 1 0 0 3 0 0 never Idle
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
AS number of neighbor Prefixes they will be announcing Ip address for peering
----------------------------- ---------------------------------------- ---------------------------
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:
router bgp 100 neighbor XP-peers peer-group neighbor XP-peers filter-list 99 out neighbor XP-peers description Exchange Point Peers .. neighbor 18.104.22.168 remote-as 200 neighbor 22.214.171.124 peer-group XP-peers neighbor 126.96.36.199 filter-list 43 in neighbor 188.8.131.52 remote-as 300 neighbor 184.108.40.206 peer-group XP-peers neighbor 220.127.116.11 filter-list 45 in neighbor 18.104.22.168 remote-as 400 neighbor 22.214.171.124 peer-group XP-peers neighbor 126.96.36.199 filter-list 47 in
ip as-path access-list 99 permit ^$
Our Inbound prefix lists will vary for each peer as we will only be accepting only our peersí prefix from each.