Lab Overview & Objectives
ReadYou will configure four LANs interconnected by four routers. Every device — PCs and router interfaces — will be statically assigned. There is no DHCP. Your job is to plan the addressing for the WAN links between routers, configure all interfaces, and write the static routes that allow PC0 to ping PC7 all the way across the network.
ip route commands for every remote network · Verify reachability with ping and tracert.
Topology Reference
Devices & Required Final State
PC0
PC1
PC2
PC3
PC4
PC5
PC6
PC7
Phase 1 — Plan Your WAN Subnets
3 tasksThe four LANs are already addressed for you (192.168.10/20/30/40.0/24). But the three router-to-router links need their own subnets — and you have to design them.
Plan your three WAN subnets below. Use any private space you want (RFC1918 — 10.0.0.0/8, 172.16.0.0/12, or 192.168.0.0/16) but pick subnets that don't overlap with the LANs. A clean choice is 10.0.0.0/30, 10.0.0.4/30, 10.0.0.8/30.
| Link | Network/Mask | Router (left) IP | Router (right) IP |
|---|---|---|---|
| WAN A: R0 ↔ R1 | |||
| WAN B: R1 ↔ R2 | |||
| WAN C: R2 ↔ R3 |
Phase 2 — Configure the PCs
8 tasksFor each PC: click the device → Desktop tab → IP Configuration. Choose Static and enter the IP, subnet mask (255.255.255.0), and default gateway.
Phase 3 — Configure Router Interfaces
4 tasksOpen each router's CLI tab. Enter the LAN interface IP (always .1 of that LAN) and the WAN interface IP(s) you planned in Phase 1. Don't forget no shutdown on every interface you touch!
enable configure terminal interface GigabitEthernet0/0/0 description LAN to SwitchX ip address <ip> <mask> no shutdown exit
Use whatever interface numbering matches your cabling in Packet Tracer (typically G0/0/0 for the LAN and G0/0/1, G0/0/2 for WAN sides). Hover over the green/red link arrows in Packet Tracer to confirm which interface is which.
R0 needs
R1 needs
R2 needs
R3 needs
Phase 4 — Test Local & Direct Connectivity
4 tasksBefore adding any routes, verify that everything directly connected works. If these pings fail, your routes will never work — fix the basics first.
no shutdown? Run show ip interface brief. (2) Are the IPs on the same /30 subnet? (3) Did you cable the right interfaces in Packet Tracer?
Phase 5 — Configure Static Routes
4 tasksEach router automatically knows about networks it's directly connected to. For every other network in the topology, you must tell the router how to reach it.
ip route <destination-network> <mask> <next-hop-IP>Example:
ip route 192.168.40.0 255.255.255.0 10.0.0.2 means "to reach the 192.168.40.0/24 network, send packets to 10.0.0.2."
Plan your routes (one row per remote network on each router)
R0 — directly connected: 192.168.10.0/24 and WAN A. Remote networks needed:
- 192.168.20.0/24 (R1's LAN)
- 192.168.30.0/24 (R2's LAN)
- 192.168.40.0/24 (R3's LAN)
- WAN B (between R1 and R2)
- WAN C (between R2 and R3)
ip route 0.0.0.0 0.0.0.0 <R1's WAN-A IP>. R3 has the same property in reverse. Try writing them out the long way first to understand what's happening, then replace with a default if you want.
R1 — directly connected: 192.168.20.0/24, WAN A, WAN B. Remote networks needed:
- 192.168.10.0/24 → next hop is R0 (across WAN A)
- 192.168.30.0/24 → next hop is R2 (across WAN B)
- 192.168.40.0/24 → next hop is R2 (across WAN B)
- WAN C → next hop is R2
R2 — directly connected: 192.168.30.0/24, WAN B, WAN C. Remote networks needed:
- 192.168.10.0/24 → next hop is R1 (across WAN B)
- 192.168.20.0/24 → next hop is R1 (across WAN B)
- 192.168.40.0/24 → next hop is R3 (across WAN C)
- WAN A → next hop is R1
R3 — directly connected: 192.168.40.0/24 and WAN C. Remote networks needed:
- Same as R0 but mirrored — five remote networks all reachable through R2. (Default route candidate!)
copy running-config startup-config (or just write) so your config survives a reload.
Phase 6 — End-to-End Verification
6 tasksThe moment of truth. Use the PC Command Prompt (Desktop tab → Command Prompt).
Things to Think About
ReflectBefore you submit, take a few minutes to think (or write) about these questions. Real understanding comes from the "why," not the "how."
- Why use a /30 for the WAN links instead of a /24 like the LANs? What would change if you used a /24 there?
- What happens if you forget one static route on one router? Where does the traffic actually fail — going out, or coming back? How does that show up in
tracert? - R0 and R3 each have only one path to the rest of the network. That makes them perfect candidates for a default route. Why would using a default route be a bad idea on R1 or R2?
- If we added a fifth router and a fifth LAN, how many new
ip routecommands would you need to type on the existing four routers? What does that tell you about how static routing scales? - What's the difference between a route destination network and a next-hop address? Why is the next hop always on a directly connected subnet?
- Why does each PC need a default gateway — but a router doesn't always need one? (Hint: think about what a router knows by default vs. what a PC knows.)
- If a link between two routers goes down, what happens to your static routes? Does the network "heal itself"? How would dynamic routing (OSPF, EIGRP) behave differently?
- You can write a static route two ways:
ip route 192.168.40.0 255.255.255.0 10.0.0.2(next-hop IP) orip route 192.168.40.0 255.255.255.0 GigabitEthernet0/0/1(exit interface). When might one be better than the other?