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MikroTik MTCINE lab 2 of 12

iBGP over loopbacks with next-hop-self and eBGP multihop

Fernvale adds a second upstream at a second edge router. Build an iBGP full mesh between loopbacks over OSPF, fix the classic next-hop problem with next-hop-self, and peer with the new upstream over two parallel links using eBGP multihop between loopbacks.

Run this lab

It needs Lite: its 5 nodes are set to 5 vCPU and 1,280 MB in total. That fits the free demo too.

In your workspace: Shared, then MikroTik MTCINE RouterOS v7 guided labs, then 02 - iBGP over loopbacks with next-hop-self and eBGP multihop

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Level
Intermediate
Time
About 75 minutes
Nodes need
5 vCPU, 1,280 MB
Smallest plan
Lite

The scenario

Fernvale has grown: EDGE1 peers with Northgate (AS 64510, done in lab 1), the new EDGE2 connects to a second upstream, Eastbridge Carrier (AS 64511), over two parallel 1G links, and CORE in the middle hosts Fernvale's servers on 198.51.100.0/25. OSPF already carries the three loopbacks. BGP does not yet run inside Fernvale, so CORE knows nothing about the Internet, and Eastbridge is waiting for EDGE2's session.

RouterLoopbackLinks
EDGE110.255.255.1ether1 203.0.113.2/30 (Northgate) · ether2 10.0.12.1/30
CORE10.255.255.2ether1 10.0.12.2/30 · ether2 10.0.23.1/30 · lan 198.51.100.1/25
EDGE210.255.255.3ether1 10.0.23.2/30 · ether2 192.0.2.2/30 · ether3 192.0.2.6/30 (Eastbridge)
EASTBRIDGE192.0.2.254ether1 192.0.2.1/30 · ether2 192.0.2.5/30 · Internet 198.18.2.0/24

What you’ll practise

  • Explain why iBGP needs a full mesh (or route reflection) and why it peers between loopbacks
  • Build iBGP connections with local.address and an IGP that carries the loopbacks
  • Recognise an unusable iBGP next hop and fix it with nexthop-choice=force-self
  • Peer eBGP between loopbacks across parallel links with multihop and ECMP static routes

The tasks

  1. Check the starting point
  2. Build the iBGP full mesh between loopbacks
  3. Find and fix the next-hop problem
  4. Peer with Eastbridge over two links with eBGP multihop
  5. Prove it end to end

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 iBGP over loopbacks with next-hop-self and eBGP multihop5 nodes, 5 links. Every link is listed as text below the diagram.NORTHGATEEDGE1COREEDGE2EASTBRIDGEether1ether1ether2ether1ether3ether2ether2ether1ether2ether1
5 nodes, with the interface names each link uses. On a narrow screen, scroll the diagram sideways.
Every link, as text
  • NORTHGATE ether1 to EDGE1 ether1
  • EDGE1 ether2 to CORE ether1
  • CORE ether2 to EDGE2 ether1
  • EDGE2 ether2 to EASTBRIDGE ether1
  • EDGE2 ether3 to EASTBRIDGE ether2
Nodes in iBGP over loopbacks with next-hop-self and eBGP multihop, with the image each runs and the vCPU and RAM it’s set to
NodeDeviceImage in Add NodeSet to
NORTHGATEMikroTik RouterOSmikrotik-7.14.21 vCPU, 256 MB
EDGE1MikroTik RouterOSmikrotik-7.14.21 vCPU, 256 MB
COREMikroTik RouterOSmikrotik-7.14.21 vCPU, 256 MB
EDGE2MikroTik RouterOSmikrotik-7.14.21 vCPU, 256 MB
EASTBRIDGEMikroTik 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 MikroTik MTCINE RouterOS v7 guided labs.

  3. Open 02 - iBGP over loopbacks with next-hop-self and eBGP multihop 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 MikroTik. The lab follows exam topics and isn’t vendor training material; vendor names identify the exams and the images in the workspace.