AI Network Labs 05 — Lab: Static and Default Routing

Three routers in a line, a LAN at each end. No routing protocol: every router learns remote networks only because you told it. Static routing is tedious by hand — which makes it perfect for checking whether you (and the AI) really understand next hops.

1 · Plan

LAN-A ── R1 ──────── R2 ──────── R3 ── LAN-C
192.168.1.0/24   10.1.12.0/30   10.1.23.0/30   192.168.3.0/24

2 · Expected routes

R1 and R3 are stub routers — one way out — so a default route is cleaner than a list:

! R1
ip route 0.0.0.0 0.0.0.0 10.1.12.2

! R3
ip route 0.0.0.0 0.0.0.0 10.1.23.1

! R2 needs specific routes to both LANs
ip route 192.168.1.0 255.255.255.0 10.1.12.1
ip route 192.168.3.0 255.255.255.0 10.1.23.2

3 · Prompt

Build three 2911 routers in a line, R1–R2–R3, with a PC on a switch at each end.
Use the addressing table I give you (paste table).
Configure static routing: default routes on R1 and R3, specific routes on R2.
Show all commands first. Then ping PC on LAN-A → PC on LAN-C and report getPduResults.

4 · Verify

show ip route

On R2 you should see two C (connected) /30s, two L local routes, and two S static routes. On R1, look for S* 0.0.0.0/0 [1/0] via 10.1.12.2.

Exercise

Delete R2's route to 192.168.3.0/24. The ping from LAN-A to LAN-C fails — but at which router does the packet die, and what ICMP message comes back? Step the simulation to confirm.