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Peering & IXP Lab (Part 2: Private Peering)

The purpose of this part of the lab is to set up private peering between adjacent autonomous systems. In our case, AS101 will private peer with AS102, AS103 with AS104, and AS105 with AS106. We will use what we have learned so far to ensure that the adjacent ASNs only hear the routes they are meant to hear - a true private peering.

Lab Topology

The lab topology has been enhanced according to the diagram below. We simply add in the peering links mentioned in the preamble.

Adding Private Peering

Each group should now configure the private peering links as shown in the diagram.

Agree on which addresses should be used for the point to point links. Typically one group will contribute the IPv4 /30 and IPv6 /127 on the link.

interface GigabitEthernet 2/0
 description Link to Group 2 Peering Router
 ip address
 ipv6 address 2001:DB8:10:12::/127

Once the interfaces have been configured make sure that the links can be pinged on both IPv4 and IPv6 endpoints.

Configuring IS-IS

Do not configure IS-IS towards your private peer! They are not part of your autonomous system.

Configuring eBGP

We now configure eBGP with the private peer. Don’t forget to filter what you hear from the private peer, and what you send to them. You should only accept their address blocks from them (they may send you more by mistake!), and you should only send prefixes you originated!

Here is a configuration example for AS103 - note that we are reusing some configuration we have set up earlier:

ip prefix-list AS103-block permit
ipv6 prefix-list AS103-v6block permit 2001:DB8:30::/48
ip prefix-list AS104-block permit
ipv6 prefix-list AS104-v6block permit 2001:DB8:40::/48
router bgp 103
 address-family ipv4
  neighbor remote-as 104
  neighbor description eBGP with AS104
  neighbor password cisco
  neighbor prefix-list AS103-block out
  neighbor prefix-list AS104-block in
 address-family ipv6
  neighbor 2001:DB8:30:12::1 remote-as 104
  neighbor 2001:DB8:30:12::1 description eBGP with AS104
  neighbor 2001:DB8:30:12::1 password cisco
  neighbor 2001:DB8:30:12::1 prefix-list AS103-v6block out
  neighbor 2001:DB8:30:12::1 prefix-list AS104-v6block in

Once this has been configured, you should now see your private peer originated routes coming from them, and you should be able to see your aggregate being sent to your private peer. The commands to see what you are receiving are:

show ip bgp neigh routes
show bgp ipv6 uni neigh 2001:DB8:30:12::1 routes

and to show what you are sending:

show ip bgp neigh advertised-routes
show bgp ipv6 uni neigh 2001:DB8:30:12::1 advertised-routes


Check on the Border, Core, Access and Peering Routers for what you now see in the BGP table.

What is the best path to your private peer? What does trace route tell you?

Hopefully you will see that the best path to your private peer will be via the private peering link. And the routes to the rest of the class will be via your upstream provider’s default route. If this is not the case, you will need to start doing some troubleshooting!

2016/pacnog19-routing/peering-ixp-part2.txt · Last modified: 2016/11/30 23:01 by philip