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Diamond, two paths 09 — default routes repair
Enterprise Intermediate 6 devices 3 checked tasks 48 points Plan lab
Scenario — Indore and Puducherry are joined by two paths, one through Hubli and one through Aizawl. Everything was configured last week and the network worked. Today the end offices cannot reach each other: one spoke points its default route at an address that is not its neighbour. Find it, fix it and prove the end-to-end paths again. You build it in a browser, type real commands at each device, and every task below is
checked against the running configuration — so you find out it is wrong before anybody else does.
Open this lab in the simulator
The simulator runs in your browser with nothing to install. This lab is part of the full simulator: open it free for 7 days with a new account, then with a plan. It needs an account, which keeps your progress.
The scenario
Indore and Puducherry are joined by two paths, one through Hubli and one through Aizawl. Everything was configured last week and the network worked. Today the end offices cannot reach each other: one spoke points its default route at an address that is not its neighbour. Find it, fix it and prove the end-to-end paths again.
Your role: a network engineer on the enterprise team. Level: Intermediate Done when: all 3 goals show as passed (48 points).
Network status
Devices: 4 routers, 2 PCs, cabled as drawn. No Layer 1 or Layer 2 faults: every link is connected and up. R-Indore starts with addresses (G0/0 10.28.1.1/24, G0/1 172.24.8.1/30, G0/2 172.24.8.5/30) and static routes already configured. PC-Indore is a host with 10.28.1.10/24, gateway 10.28.1.1. R-Hubli starts with addresses (G0/0 172.24.8.2/30, G0/1 172.24.8.9/30) and static routes already configured. R-Aizawl starts with addresses (G0/0 172.24.8.6/30, G0/1 172.24.8.13/30) and static routes already configured. R-Puducherry starts with addresses (G0/0 10.28.2.1/24, G0/1 172.24.8.10/30, G0/2 172.24.8.14/30) and static routes already configured. PC-Puducherry is a host with 10.28.2.10/24, gateway 10.28.2.1. Known problems
A ping from 10.28.1.10 to 10.28.2.10 times out although every link is up. No cable or interface is faulty: the fault is one line of configuration on one router. Everything else is correct and must be left alone. Goals
R-Puducherry: a route — default via 172.24.8.9 (8 pts) 10.28.1.10 (Indore) reaches 10.28.2.10 (Puducherry) (20 pts) 10.28.2.10 (Puducherry) reaches 10.28.1.10 (Indore) (20 pts) The activity, in order
Confirm the symptom: ping the far PC from the near PC and note where it fails. Why: The next hop must be an address on a directly connected subnet, or the route never enters the table. Verify with: show ip route Follow the path hop by hop. On each router read its neighbours and its routes, starting with the one nearest the failure. Why: A ping needs a route in BOTH directions. This is the end-to-end proof that everything before it worked. Verify with: ping 10.28.2.10 Compare the suspect router with its neighbour: the same protocol, the same numbers, every link covered. Why: A ping needs a route in BOTH directions. This is the end-to-end proof that everything before it worked. Verify with: ping 10.28.1.10 Fix the single wrong line and nothing else. Check: show running-config Retest: neighbours, routes, then pings in both directions. Check: show ip route, then ping Tips
Work in the order given: later goals depend on the earlier ones. After every change, run the verify command before moving on; do not guess. Stuck? Read the verify output first. It names the interface, neighbour or route that is wrong. Common mistake: Pointing the default route at the wrong neighbour address Common mistake: Forgetting the head-end needs specific routes back to every branch Common mistake: Leaving a transit router without the routes to LANs beyond it Why this matters
A branch does not need to know every network. A default route toward the head-end handles everything unknown, while the head-end carries the specific routes — the standard hub-and-spoke design for small sites.
What you will be able to do
Choose between a default route and specific routes
Point a default route at the correct neighbour
Read the gateway of last resort in show ip route
The network
ISR 2911, PC — 6 devices in all, already cabled.
Fa0 Gi0/0 10.28.1.1/24 Fa0 Gi0/0 10.28.2.1/24 Gi0/1 172.24.8.1/30 Gi0/0 172.24.8.2/30 Gi0/2 172.24.8.5/30 Gi0/0 172.24.8.6/30 Gi0/1 172.24.8.9/30 Gi0/1 172.24.8.10/30 Gi0/1 172.24.8.13/30 Gi0/2 172.24.8.14/30 R-Indore PC-Indore 10.28.1.10/24 · gw 10.28.1.1 R-Hubli R-Aizawl R-Puducherry PC-Puducherry 10.28.2.10/24 · gw 10.28.2.1 Drawn from this lab: devices, cables, ports and the addresses already set. Device Model Address already set
R-Indore ISR 2911 configure it PC-Indore PC 10.28.1.10 / 255.255.255.0 gw 10.28.1.1 R-Hubli ISR 2911 configure it R-Aizawl ISR 2911 configure it R-Puducherry ISR 2911 configure it PC-Puducherry PC 10.28.2.10 / 255.255.255.0 gw 10.28.2.1
Cabling
PC-Indore Fa0 ↔ R-Indore Gi0/0 PC-Puducherry Fa0 ↔ R-Puducherry Gi0/0 R-Indore Gi0/1 ↔ R-Hubli Gi0/0 R-Indore Gi0/2 ↔ R-Aizawl Gi0/0 R-Hubli Gi0/1 ↔ R-Puducherry Gi0/1 R-Aizawl Gi0/1 ↔ R-Puducherry Gi0/2
What is configured at the start
These are already configured when the lab opens — including, where this is a troubleshooting lab, the fault itself:
R-Indore interface g0/0
ip address 10.28.1.1 255.255.255.0
no shutdown
exit
interface g0/1
ip address 172.24.8.1 255.255.255.252
no shutdown
exit
interface g0/2
ip address 172.24.8.5 255.255.255.252
no shutdown
exit
ip route 10.28.2.0 255.255.255.0 172.24.8.2 R-Hubli interface g0/0
ip address 172.24.8.2 255.255.255.252
no shutdown
exit
interface g0/1
ip address 172.24.8.9 255.255.255.252
no shutdown
exit
ip route 0.0.0.0 0.0.0.0 172.24.8.1
ip route 10.28.2.0 255.255.255.0 172.24.8.10 R-Aizawl interface g0/0
ip address 172.24.8.6 255.255.255.252
no shutdown
exit
interface g0/1
ip address 172.24.8.13 255.255.255.252
no shutdown
exit
ip route 0.0.0.0 0.0.0.0 172.24.8.5
ip route 10.28.2.0 255.255.255.0 172.24.8.14 R-Puducherry interface g0/0
ip address 10.28.2.1 255.255.255.0
no shutdown
exit
interface g0/1
ip address 172.24.8.10 255.255.255.252
no shutdown
exit
interface g0/2
ip address 172.24.8.14 255.255.255.252
no shutdown
exit
ip route 0.0.0.0 0.0.0.0 172.24.8.3 Tasks, and how each one is checked
Every task is decided by reading the live network — a neighbour in FULL, a ping that succeeds, a line in the running configuration — not by looking for a keyword you typed. The same command shows you what the lab sees.
# Task Pts How to verify it yourself
1 R-Puducherry: a route — default via 172.24.8.9 8 On R-Puducherry: show ip route 0.0.0.0 shows next hop 172.24.8.9. 2 10.28.1.10 (Indore) reaches 10.28.2.10 (Puducherry) 20 On PC-Indore: ping 10.28.2.10 must succeed. 3 10.28.2.10 (Puducherry) reaches 10.28.1.10 (Indore) 20 On PC-Puducherry: ping 10.28.1.10 must succeed.
Stuck? Ask the coach
Tell the coach what you see or what you tried. It gives you a hint, not the answer, the way a senior engineer would. Included with a free trial or any plan.
Ask the coach
Common mistakes
Pointing the default route at the wrong neighbour address
Forgetting the head-end needs specific routes back to every branch
Leaving a transit router without the routes to LANs beyond it
Reference solution
Try it yourself first — the lab checks your work either way. This is one configuration that makes every task pass, device by device:
R-Puducherry no ip route 0.0.0.0 0.0.0.0 172.24.8.3
ip route 0.0.0.0 0.0.0.0 172.24.8.9 Where this is examined
CCNA 3.0 default routing; CCNP ENARSI static routing.
This lab practises these topics in the zNetLaB certification courses:
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