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BGP in depth lab 6 of 14

Confederations and their attribute rules

Kestrel Fibre has bought Wharfe Telecom, and the two networks must look like one AS from outside without a flag-day iBGP redesign. Build a confederation across IOS and EOS, then prove which attributes survive a sub-AS boundary, how the AS path changes shape, and what one missing line does.

Run this lab

It needs Lite: its 6 nodes are set to 6 vCPU and 4,608 MB in total. That fits the free demo too.

In your workspace: Shared, then BGP in depth guided labs, then 06 - Confederations and their attribute rules

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Level
Advanced
Time
About 80 minutes
Nodes need
6 vCPU, 4,608 MB
Smallest plan
Lite

The scenario

Kestrel Fibre (AS 64500) has bought Wharfe Telecom. Customers and peers must keep seeing one AS, 64500, but the two engineering teams want to keep running their own iBGP domains. Your manager has picked a confederation: each team keeps a private sub-AS, and the routers between them speak a special form of eBGP.

ItemValue
Confederation identifier (what the world sees)64500
Sub-AS 65001 (Kestrel)R1, R2
Sub-AS 65002 (Wharfe)R3, EOS1
E1, AS 64510Sends 198.51.100.0/25 (prefix A, with MED 77) and 198.51.100.128/25 (prefix B)
E2, AS 64520Sends 192.0.2.0/24 (prefix C), and hears A and B from E1 too
DeviceInterfaceAddressConnects to
R1Loopback010.255.0.1/32
R1Loopback1203.0.113.1/25
R1Gi0/010.0.12.1/30R2 Gi0/0
R1Gi0/1172.16.15.1/30E1 Gi0/0
R2Loopback010.255.0.2/32
R2Gi0/010.0.12.2/30R1 Gi0/0
R2Gi0/110.0.23.1/30R3 Gi0/0
R3Loopback010.255.0.3/32
R3Gi0/010.0.23.2/30R2 Gi0/1
R3Gi0/110.0.34.1/30EOS1 Ethernet1
EOS1Ethernet110.0.34.2/30R3 Gi0/1
EOS1Ethernet2172.16.46.1/30E2 Gi0/0
EOS1Loopback010.255.0.4/32
EOS1Loopback1203.0.113.129/25
E1Loopback010.255.0.5/32
E1Loopback1198.51.100.1/25
E1Loopback2198.51.100.129/25
E1Gi0/0172.16.15.2/30R1 Gi0/1
E1Gi0/1172.16.56.1/30E2 Gi0/1
E2Loopback010.255.0.6/32
E2Loopback1192.0.2.1/24
E2Gi0/0172.16.46.2/30EOS1 Ethernet2
E2Gi0/1172.16.56.2/30E1 Gi0/1

What you’ll practise

  • Explain what a confederation is and how it differs from route reflection
  • Configure sub-ASes, the confederation identifier and confederation peers on IOS and EOS
  • Read AS_CONFED_SEQUENCE in an AS path and say why it doesn't count towards path length
  • Prove that LOCAL_PREF, MED and NEXT_HOP cross a sub-AS boundary unchanged
  • Prove that outside peers see only the confederation identifier
  • Explain what breaks when bgp confederation peers is missing

The tasks

  1. Why a confederation, and what it is
  2. Build sub-AS 65001
  3. Build sub-AS 65002 on IOS and EOS
  4. Join the sub-ASes
  5. Prove the attribute rules
  6. Prove what outsiders see
  7. The path that doesn't count
  8. Break it on purpose
  9. Prove the data path

The Lab Tasks pane has the scenario, these tasks, the checks to run, hints and the full solution.

Topology and devices

The network as it opens in EVE-NG, drawn from the lab’s own canvas, and the image each node runs.

Topology of Confederations and their attribute rules6 nodes, 6 links. Every link is listed as text below the diagram.R1R2R3EOS1E1E2Gi0/0Gi0/0Gi0/1Gi0/0Gi0/1Ethernet1Gi0/1Gi0/0Ethernet2Gi0/0Gi0/1Gi0/1
6 nodes, with the interface names each link uses. On a narrow screen, scroll the diagram sideways.
Every link, as text
  • R1 Gi0/0 to R2 Gi0/0
  • R2 Gi0/1 to R3 Gi0/0
  • R3 Gi0/1 to EOS1 Ethernet1
  • R1 Gi0/1 to E1 Gi0/0
  • EOS1 Ethernet2 to E2 Gi0/0
  • E1 Gi0/1 to E2 Gi0/1
Nodes in Confederations and their attribute rules, with the image each runs and the vCPU and RAM it’s set to
NodeDeviceImage in Add NodeSet to
R1Cisco IOSvvios-adventerprisek9-m.spa.159-3.m91 vCPU, 512 MB
R2Cisco IOSvvios-adventerprisek9-m.spa.159-3.m91 vCPU, 512 MB
R3Cisco IOSvvios-adventerprisek9-m.spa.159-3.m91 vCPU, 512 MB
EOS1Arista vEOSveos-4.33.1.1F1 vCPU, 2,048 MB
E1Cisco IOSvvios-adventerprisek9-m.spa.159-3.m91 vCPU, 512 MB
E2Cisco IOSvvios-adventerprisek9-m.spa.159-3.m91 vCPU, 512 MB

How to open this lab

  1. Sign in to your workspace at lab.cloudlabbox.com.

  2. In File Manager, open Shared, then the folder BGP in depth guided labs.

  3. Open 06 - Confederations and their attribute rules and start its nodes, then open Lab Tasks for the scenario and the steps.

The lab is read-only. You can start the nodes and configure the devices, but changes to the topology can’t be saved. To change it, rebuild it in your own folder.

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CloudLabBox is independent of Arista Networks, Cisco, Juniper Networks and MikroTik. The lab follows exam topics and isn’t vendor training material; vendor names identify the exams and the images in the workspace.