CCNA Lab: VLSM Right-Sizing from One /24

Bundle lab

Practice deterministic VLSM planning and interface addressing on two Cisco IOS routers. Starting from a single /24, allocate three right-sized IPv4 subnets (two LANs represented by loopbacks and one router-to-router WAN) and configure exact interface addresses and masks. No routing protocols or static routes are configured; verification focuses on directly connected reachability and show commands.

Learning objectives

• Plan a VLSM allocation from a single /24 to meet distinct host requirements with minimal waste
• Apply deterministic IPv4 interface addressing on IOS (ip address <addr> <mask> + no shutdown)
• Use loopbacks to represent LAN gateways without revealing answers via pre-addressed hosts
• Verify interface state and directly connected reachability with show and ping

Troubleshooting focus

• If the WAN ping fails, verify both sides use the same /30 mask and each is within the correct usable range; a mask mismatch or out-of-subnet IP prevents ARP/neighbor resolution.
• If an interface shows administratively down, add no shutdown under the interface and re-check cabling in the topology view.
• If a loopback shows no IP, confirm you used the first usable address in the correct subnet and the dotted-decimal mask that matches your derived prefix.
• If you see overlapping or duplicate subnets, re-run the largest-to-smallest allocation process and re-apply the deterministic tie-break rules.