Open the lab
[ YOUR LAB FILE ]
Download the starting topology, then work through the lesson in SwitchLab.
- Save the .swlab file without renaming its extension.
- Open SwitchLab. Import and export controls currently require a desktop-width window. On a smaller screen, Tools → Fit brings the topology into view.
- Select Import Sandbox (folder icon), choose the downloaded file, and confirm the device and cable counts below.
- Select a device, then choose Open device on desktop or its name in the bottom bar on smaller screens. Select CLI for switches/routers or Desktop → Terminal for PCs. Enter
enableonly when the prompt ends in >. - Follow this page beside the simulator. Use a free account to export your work. Reimport the original download to restart; export any work you want to keep first.
Prerequisites
- Configure router interfaces and read a routing table.
- Understand /24 LANs, a /30 transit subnet, and next-hop addresses.
Topology

4 devices · 3 links
Scenario
HQ and a small branch have a working point-to-point Ethernet connection. Interfaces and PCs are already addressed, but neither router knows the remote LAN. HQ requires a specific branch route; the stub branch sends unknown destinations toward HQ.
Objectives
- Inspect connected routes and identify the two missing forwarding decisions.
- Install an IPv4 network route at HQ and a default route at the branch.
- Verify route type, next hop, and delivery in both directions.
CCNA blueprint
200-301 v1.1 objectives — this lab covers the following specific skills, not every subtopic in the domain.
- 3.1.a — Read the static route code.
- 3.1.d — Identify the next hop.
- 3.3.a — Configure and verify an IPv4 default route.
- 3.3.b — Configure and verify an IPv4 network route; IPv6 is outside this lab.
Starting information
- R1 is HQ and R2 is the stub branch. Their g0/0 interfaces face the local PCs; g0/1 interfaces share 10.0.12.0/30.
- PC1 is 10.10.10.10/24 via 10.10.10.1. PC2 is 10.20.20.20/24 via 10.20.20.1.
- Physical interfaces are enabled and correctly addressed. There are no static routes or dynamic routing processes.
| Host | IPv4 address | Mask | Gateway |
|---|---|---|---|
| PC1 | 10.10.10.10 | 255.255.255.0 | 10.10.10.1 |
| PC2 | 10.20.20.20 | 255.255.255.0 | 10.20.20.1 |
| Router | Interface | IPv4 address | Mask |
|---|---|---|---|
| R1 | g0/0 | 10.10.10.1 | 255.255.255.0 |
| R1 | g0/1 | 10.0.12.1 | 255.255.255.252 |
| R2 | g0/0 | 10.20.20.1 | 255.255.255.0 |
| R2 | g0/1 | 10.0.12.2 | 255.255.255.252 |
| Device / port | Device / port |
|---|---|
| PC1 / eth0 | R1 / g0/0 |
| R1 / g0/1 | R2 / g0/1 |
| PC2 / eth0 | R2 / g0/0 |
Tasks
- Prove that each PC reaches its local gateway and that R1 reaches R2 over the transit network. Record why the remote ping fails.
- On R1, install exactly one route to 10.20.20.0/24 through R2’s transit address.
- On R2, install a default route toward R1. Do not add a dynamic routing protocol or change addressing.
- Inspect both routing tables. Verify the specific static route on R1 and gateway of last resort on R2.
- Verify PC1-to-PC2 and PC2-to-PC1 pings, explain the return path, and save the router configurations.
Useful commands
show ip interface brief
show ip route
show running-config
ping 10.0.12.2
ip route <network> <mask> <next-hop>
copy running-config startup-configProgressive hints
Hint 1
Each router already knows its directly connected networks. Compare the destination LAN with those entries.
Hint 2
The forward packet and the reply each need a route. R1 needs the branch /24; R2 can use its only exit as the default.
Hint 3
The next hops are the peer addresses on 10.0.12.0/30. A default route uses destination 0.0.0.0 and mask 0.0.0.0.
Verification
- Each PC still reaches its local gateway.
- R1 shows S 10.20.20.0/24 via 10.0.12.2.
- R2 shows a static default 0.0.0.0/0 via 10.0.12.1 and identifies its gateway of last resort.
- PC1 → 10.20.20.20 and PC2 → 10.10.10.10 both succeed.
Solution / walkthrough
Show Solution
Use enable only from a > prompt; if already at #, begin with configure terminal.
R1
Use the directly connected peer as the next hop for the branch LAN.
enable
configure terminal
ip route 10.20.20.0 255.255.255.0 10.0.12.2
end
copy running-config startup-configR2
The stub branch has a single exit. Its default route also carries replies to HQ.
enable
configure terminal
ip route 0.0.0.0 0.0.0.0 10.0.12.1
end
copy running-config startup-configRun every verification check above after the changes. A saved configuration alone does not prove packet delivery.