BGP Lab 2: Exact-Match Prefix Origination

Bundle lab

Configure eBGP between two routers and originate select connected /24s using the exact-match 'network ... mask' command. Verify that only the intended prefixes are advertised and learned by the neighbor, and use host-based tests to confirm reachability to the advertised networks. This beginner CCNP lab reinforces that the BGP network statement only advertises a route if an exact match exists in the RIB, and that the 'mask' keyword is mandatory for non-classful advertisements.

Learning objectives

• Stand up an eBGP session over a directly connected /30 with correct neighbor remote-as on both ends.
• Originate specific connected routes into BGP using the exact-match 'network A.B.C.D mask M.M.M.M' syntax.
• Demonstrate why the mask keyword is required for non-classful prefixes and how omission silently prevents advertisement.
• Verify advertised and received routes using 'show ip bgp', 'show ip bgp neighbors ... advertised-routes', and 'show ip route bgp'.
• Validate reachability from a LAN host behind the eBGP neighbor to the originated prefixes and confirm that non-originated routes remain unreachable.

Troubleshooting focus

• Neighbor stuck in Idle/Active due to incorrect remote-as or wrong neighbor IP.
• Expected prefixes missing on the neighbor because the 'mask' keyword is omitted or the exact route is absent from the RIB.
• Host reachability asymmetry when return routing to the host's LAN is missing.
• Accidental advertisement of unintended subnets when using overly broad network statements.
• Misinterpreting 'show ip bgp neighbors advertised-routes' vs 'received-routes' and drawing incorrect conclusions.