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AdvancedPublished 2026-07-03

Lab 9: Path Selection with Weight (First Tiebreaker)

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In this advanced CCNP BGP lab, you will steer a single router's outbound path choice using Cisco's Weight attribute, the very first BGP best-path tiebreaker. R1 (AS 65001) peers eBGP with two ISPs (R2 in AS 65002 and R3 in AS 65003). Both ISPs advertise the same prefix 172.16.50.0/24. Your job is to make R1 prefer the R3 path using the neighbor weight command and verify the outcome using IOS and Linux tools.

Track
Est. time
45 minutes
Difficulty
Advanced
Topics

Learning objectives

  • Configure and verify parallel eBGP sessions over separate /30 transits.
  • Originate and receive an identical prefix from two neighbors and view candidate paths.
  • Understand and apply BGP Weight to influence a single router's local decision.
  • Contrast Weight (local-only) with Local Preference (AS-wide) in best-path order.
  • Validate path selection with show ip bgp and data-plane tests from a host.

Troubleshooting focus

  • If only one path is visible on R1, confirm both eBGP sessions are configured symmetrically with correct remote-as values and the /30 addressing matches on each side.
  • If the 172.16.50.0/24 route is missing, verify Loopback1 at 172.16.50.1/24 exists on both R2 and R3, and that network 172.16.50.0 mask 255.255.255.0 is configured under BGP on each.
  • If Weight appears set but not taking effect, ensure the neighbor address in the weight command exactly matches the eBGP neighbor and confirm both paths are otherwise tied.
  • If data-plane tests fail from the host, verify the host default gateway, R1 LAN addressing, and that R1 holds a BGP route to 172.16.50.0/24 with next-hop toward R3.

Topology

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Grade your work

How this lab is graded
  • Build it your way. Where a lab lets you choose a value — a VLAN name, an interface description — grading checks that you configured it, not which name you picked. Names that another line has to reference, like an ACL applied with access-class, are stated in the guide and do have to match.
  • Addresses, modes and protocol keywords are exact. An IP address, a subnet mask, switchport mode trunk, an encapsulation — these carry the meaning of the lab, so they are graded as written in the guide.
  • Grading reads your saved configuration. Export the lab from CML after you have configured it, and make sure anything you set is in the running-config — a change that only exists in a terminal session never reaches the grader.
  • You can submit as many times as you like. Your best score stands, and each attempt tells you which checks passed so you can work the gaps.
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