BGP Lab 5: Local Preference - Preferred Exit

Bundle lab

Configure and validate BGP local-preference to prefer one provider when the same destination prefix is learned from two eBGP neighbors. You will see two equal AS-PATH routes to 172.16.100.0/24 on the edge router and then apply an inbound route-map on the R2 session to set local-preference 200 so the edge prefers exiting via R2. Verification includes host pings/traceroute and router BGP best-path checks.

Learning objectives

• Build and verify eBGP sessions on directly connected /30 links
• Originate an identical service prefix from two providers and observe best-path tie-break
• Set local-preference inbound on a specific neighbor to steer outbound traffic
• Validate BGP best-path selection using show commands and end-host tests
• Differentiate between local-preference (AS-wide) and weight (local-only) in path selection

Troubleshooting focus

• If no 172.16.100.0/24 appears on RTR-EDGE-A: verify that R2 and R3 have Loopback1 with 172.16.100.1/24 and an exact-match network statement (with mask) so BGP originates the route.
• If the neighbor does not establish: check that each eBGP neighbor uses the directly connected interface IP with the correct remote-as and that the /30 addressing matches on both ends.
• If the wrong path remains best: confirm the route-map is applied inbound to the R2 neighbor, that the set local-preference value is higher than 100, and that no weight or MED policies are overriding the decision.
• If host pings fail: ensure RTR-EDGE-A originates 192.0.2.0/24 so providers have a return route to CLIENT-A, and verify default gateways on the hosts.