Point-to-Point Links with /30 and /31
Build confidence addressing IPv4 point-to-point WAN links on Cisco IOS using /30 and /31 masks. Two routers are connected by two parallel links: one classic /30 and one RFC 3021 /31. No routing protocols or static routes are configured — the goal is deterministic, correct interface addressing and verification of directly connected reachability. A small LAN off R1 with two hosts allows additional verification (host-to-gateway only).