Static Routing Capstone: Two Sites Over a /30 WAN

Archive lab

Advanced static-routing capstone, run as a fault hunt. Two suites were cut over last night and now Suite-B is unreachable, Suite-A gets replies only sometimes, and one client cannot even reach its own gateway. Nothing was written down. You get symptoms and the required end state — no fault list. The faults span both routers and the access switch, and the routing table being present does not mean it is right.

Learning objectives

• Diagnose a broken inter-suite path from operational state alone, with no list of what was changed
• Tell a black-holed route apart from a missing return route — both look like 'it does not work' from a client
• Recognise asymmetric reachability as evidence about which direction is actually broken
• Check Layer 2 before blaming Layer 3: a port in the wrong VLAN presents as a routing failure
• Repair faults on whichever device holds them, across two routers and a switch

Troubleshooting focus

• Detect and fix missing return routes that cause one-way pings
• Correct interface shutdowns and wrong port/VLAN assignments on the switch
• Resolve wrong masks or next-hop IPs that break adjacency or blackhole traffic
• Identify routing loops or defaults pointing to the wrong neighbor