CloudLabBox
Try the free demo

Arista EOS lab 7 of 20

eBGP leaf-spine underlay with ECMP and BFD

Build the routed underlay of a two-spine, two-leaf fabric the way Arista designs recommend: one private AS per leaf, a shared spine AS, peer groups, dynamic BGP peering on the spines, route-map-controlled advertisements, four-way ECMP, BFD and jumbo MTU.

Run this lab

It needs Standard: its 6 nodes are set to 6 vCPU and 9,216 MB in total.

In your workspace: Shared, then Arista EOS guided labs, then 07 - eBGP leaf-spine underlay with ECMP and BFD

Run it on Standard from £5 a day

The free demo can’t run it: it has 6 vCPU and 8 GB, and this lab’s nodes need 6 vCPU and 9,216 MB together. Every lab plan includes every guided lab.

Level
Intermediate
Time
About 80 minutes
Nodes need
6 vCPU, 9,216 MB
Smallest plan
Standard

The scenario

Northwind's first production pod is cabled: two spines, two leaves, every leaf connected to every spine with a routed /31 (addresses are already configured). The design standard says eBGP everywhere: the spines share AS 65000 and each leaf gets its own private AS, so a leaf never learns a route back through itself and every path is visible in the AS path. Your job is to build that underlay, prove both spines are used at once, and make failures heal in well under a second.

DeviceLoopback0 (router ID)ASFabric links
spine110.255.0.165000Et1 10.1.1.0/31 → leaf1 · Et2 10.1.1.2/31 → leaf2
spine210.255.0.265000Et1 10.1.2.0/31 → leaf1 · Et2 10.1.2.2/31 → leaf2
leaf110.255.0.1165001Et1 10.1.1.1 → spine1 · Et2 10.1.2.1 → spine2 · Vlan10 10.10.10.1/24
leaf210.255.0.1265002Et1 10.1.1.3 → spine1 · Et2 10.1.2.3 → spine2 · Vlan20 10.20.20.1/24
h1 / h2––10.10.10.11/24 via .1 / 10.20.20.11/24 via .1

What you’ll practise

  • Explain the eBGP underlay AS design (spines share an AS, each leaf has its own)
  • Configure BGP with peer groups on leaves and dynamic listen ranges with a peer filter on spines
  • Advertise only loopbacks and host subnets with a prefix-list and route-map
  • Enable ECMP and verify equal-cost paths through both spines
  • Speed up failure detection with BFD and test a spine link failure
  • Set jumbo MTU on fabric links and explain why VXLAN needs it

The tasks

  1. Prepare the links: jumbo MTU
  2. BGP on the leaves with a peer group
  3. Dynamic peering on the spines
  4. Advertise exactly what the fabric needs
  5. Verify ECMP and end-to-end reachability
  6. Fast failure detection with BFD

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 eBGP leaf-spine underlay with ECMP and BFD6 nodes, 6 links. Every link is listed as text below the diagram.spine1spine2leaf1leaf2h1h2Ethernet3eth0Ethernet3eth0Ethernet1Ethernet1Ethernet2Ethernet2Ethernet2Ethernet1Ethernet1Ethernet2
6 nodes, with the interface names each link uses.
Every link, as text
  • spine1 Ethernet1 to leaf1 Ethernet1
  • spine1 Ethernet2 to leaf2 Ethernet1
  • spine2 Ethernet1 to leaf1 Ethernet2
  • spine2 Ethernet2 to leaf2 Ethernet2
  • leaf1 Ethernet3 to h1 eth0
  • leaf2 Ethernet3 to h2 eth0
Nodes in eBGP leaf-spine underlay with ECMP and BFD, with the image each runs and the vCPU and RAM it’s set to
NodeDeviceImage in Add NodeSet to
spine1Arista vEOSveos-4.33.1.1F1 vCPU, 2,048 MB
spine2Arista vEOSveos-4.33.1.1F1 vCPU, 2,048 MB
leaf1Arista vEOSveos-4.33.1.1F1 vCPU, 2,048 MB
leaf2Arista vEOSveos-4.33.1.1F1 vCPU, 2,048 MB
h1Alpine Linuxclbalpinebase-alpine-base-3-20-31 vCPU, 512 MB
h2Alpine Linuxclbalpinebase-alpine-base-3-20-31 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 Arista EOS guided labs.

  3. Open 07 - eBGP leaf-spine underlay with ECMP and BFD 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.

More Arista EOS labs

All Arista EOS labs

Related labs in other courses

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