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BGP in depth lab 4 of 14

BGP communities of every size

Kestrel Fibre lets customers steer their own routes with communities. Build the menu end to end: standard communities that set local preference, the well-known no-export and no-advertise, extended route-target tags, and large communities for a customer with a 4-byte AS number, which pass straight through routers that can't read them.

Run this lab

It needs Lite: its 5 nodes are set to 5 vCPU and 3,840 MB in total. That fits the free demo too.

In your workspace: Shared, then BGP in depth guided labs, then 04 - BGP communities of every size

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Level
Advanced
Time
About 90 minutes
Nodes need
5 vCPU, 3,840 MB
Smallest plan
Lite

The scenario

Kestrel Fibre publishes a community menu, so that customers can steer their own routes without raising a ticket. You're bringing the menu to life.

CommunityMeaning
64500:120Kestrel, set local preference 120
64500:80Kestrel, set local preference 80
no-exportWell known: keep inside this AS
no-advertiseWell known: don't pass to any peer
RT 64500:20Extended: Kestrel marks portal routes with this tag
4200000020:100:1Large: set by the 4-byte AS customer, and read by the first router that understands it
PrefixOwnerTag
203.0.113.0/25EOS164500:120
203.0.113.128/25EOS164500:80
198.18.10.0/24EOS1no-export
198.18.20.0/24EOS1no-advertise
192.0.2.0/24CHR14200000020:100:1
198.51.100.0/24UP
DeviceInterfaceAddressConnects to
R1Loopback010.255.0.1/32
R1Gi0/0172.16.1.1/30EOS1 Ethernet1
R1Gi0/110.0.12.1/30R2 Gi0/0
R2Loopback010.255.0.2/32
R2Gi0/010.0.12.2/30R1 Gi0/1
R2Gi0/1172.16.2.1/30UP Gi0/0
R2Gi0/2172.16.3.1/30CHR1 ether1
EOS1Ethernet1172.16.1.2/30R1 Gi0/0
EOS1Loopback010.255.0.10/32
EOS1Loopback1203.0.113.1/25
EOS1Loopback2203.0.113.129/25
EOS1Loopback3198.18.10.1/24
EOS1Loopback4198.18.20.1/24
UPLoopback010.255.0.9/32
UPLoopback1198.51.100.1/24
UPGi0/0172.16.2.2/30R2 Gi0/1
CHR1ether1172.16.3.2/30R2 Gi0/2
CHR1lan192.0.2.1/24

What you’ll practise

  • Explain the format and purpose of standard, extended and large communities
  • Turn on sending per neighbour and per community type where a vendor needs it
  • Act on a community with a community list and a route map
  • Show exactly how no-export and no-advertise limit a route
  • Remove internal communities before routes leave the AS
  • Explain why a 4-byte AS needs large communities, and prove an optional transitive attribute crosses a router that doesn't understand it

The tasks

  1. What a community is
  2. Make communities readable and send them
  3. Act on the community
  4. no-export and no-advertise
  5. Clean up on the way out
  6. Extended communities
  7. Large communities and a 4-byte AS

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 BGP communities of every size5 nodes, 4 links. Every link is listed as text below the diagram.R1R2EOS1UPCHR1Ethernet1Gi0/0Gi0/1Gi0/0Gi0/2ether1Gi0/1Gi0/0
5 nodes, with the interface names each link uses. On a narrow screen, scroll the diagram sideways.
Every link, as text
  • EOS1 Ethernet1 to R1 Gi0/0
  • R1 Gi0/1 to R2 Gi0/0
  • R2 Gi0/1 to UP Gi0/0
  • R2 Gi0/2 to CHR1 ether1
Nodes in BGP communities of every size, 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
EOS1Arista vEOSveos-4.33.1.1F1 vCPU, 2,048 MB
UPCisco IOSvvios-adventerprisek9-m.spa.159-3.m91 vCPU, 512 MB
CHR1MikroTik RouterOSmikrotik-7.14.21 vCPU, 256 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 04 - BGP communities of every size 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.