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JNCIP-ENT lab 4 of 19

BGP route selection and next hops

Find why iBGP routes are hidden, fix next hop resolution, read why Junos chose each path, and steer traffic with local preference, prepending and MED.

Run this lab

It needs Standard: its 5 nodes are set to 11 vCPU and 11,776 MB in total.

In your workspace: Shared, then JNCIP-ENT JN0-650 guided labs, then 04 - BGP route selection and next hops

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 11 vCPU and 11,776 MB together. Every lab plan includes every guided lab.

Level
Advanced
Time
About 90 minutes
Nodes need
11 vCPU, 11,776 MB
Smallest plan
Standard

The scenario

Northmere (AS 64500) has two border routers with one ISP each. R3 is an internal router with the head office LAN. All the BGP sessions are configured and up, and OSPF runs inside the network, but something is wrong: routes from the other border router aren't being used. You'll find out why, then read how Junos picks a best path, and then bend that choice in both directions.

The ISPs use these prefixes to give you something to compare. Both ISPs originate the shared ones:

PrefixWho originates itWhat's different
203.0.113.0/24ISP-AIts own
198.51.100.0/24ISP-BIts own
192.0.2.0/24BothNothing
100.64.1.0/24BothISP-A sends origin incomplete
100.64.2.0/24BothISP-A sends MED 50, ISP-B sends MED 20
DeviceInterfaceAddress
R1ge-0/0/0, ge-0/0/2, lo010.0.12.1/30, 10.0.13.1/30, 10.255.0.1/32
R1ge-0/0/1198.18.1.1/30, to ISP-A at .2
R2ge-0/0/0, ge-0/0/2, lo010.0.12.2/30, 10.0.23.1/30, 10.255.0.2/32
R2ge-0/0/1198.18.2.1/30, to ISP-B at .2
R3Gi0/0, Gi0/1, Lo0, Lo1010.0.13.2/30, 10.0.23.2/30, 10.255.0.3/32, 10.60.1.1/24

This course uses AS numbers from the range set aside for documentation, so that private AS numbers can mean something in a later lab.

What you’ll practise

  • Diagnose an unresolved protocol next hop
  • Fix it with next-hop self
  • Work through the BGP selection steps from show route detail
  • Steer outbound traffic with local preference
  • Steer inbound traffic with AS path prepending
  • Stop your AS from carrying transit traffic
  • Compare MED across neighbouring ASs

The tasks

  1. Find the hidden routes
  2. Fix next hop resolution
  3. Read how Junos chose
  4. Steer outbound traffic with local preference
  5. Advertise your network and steer inbound traffic
  6. Compare MED between different ISPs

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 route selection and next hops5 nodes, 6 links. Every link is listed as text below the diagram.R1R2R3ISP-AISP-Bge-0/0/1Gi0/0ge-0/0/1Gi0/0ge-0/0/2Gi0/0ge-0/0/2Gi0/1ge-0/0/0ge-0/0/0Gi0/1Gi0/1
5 nodes, with the interface names each link uses.
Every link, as text
  • R1 ge-0/0/0 to R2 ge-0/0/0
  • R1 ge-0/0/1 to ISP-A Gi0/0
  • R2 ge-0/0/1 to ISP-B Gi0/0
  • R1 ge-0/0/2 to R3 Gi0/0
  • R2 ge-0/0/2 to R3 Gi0/1
  • ISP-A Gi0/1 to ISP-B Gi0/1
Nodes in BGP route selection and next hops, with the image each runs and the vCPU and RAM it’s set to
NodeDeviceImage in Add NodeSet to
R1Juniper vJunos-routervjunosrouter-24.2R1-S2.54 vCPU, 5,120 MB
R2Juniper vJunos-routervjunosrouter-24.2R1-S2.54 vCPU, 5,120 MB
R3Cisco IOSvvios-adventerprisek9-m.spa.159-3.m91 vCPU, 512 MB
ISP-ACisco IOSvvios-adventerprisek9-m.spa.159-3.m91 vCPU, 512 MB
ISP-BCisco 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 JNCIP-ENT JN0-650 guided labs.

  3. Open 04 - BGP route selection and next hops 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 JNCIP-ENT labs

All JNCIP-ENT labs

Related labs in other courses

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