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Triangle 25 — OSPF routing
Enterprise Beginner 6 devices 7 checked tasks 70 points Free lab
Scenario — Vizag, Imphal and Kozhikode are cabled in a triangle, so every office has two ways to every other. Every interface is already addressed. Your job is the routing: use OSPF so every office can reach every other. 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 is a free lab: it stays open on the free plan. It needs an account, which keeps your progress.
The scenario
Vizag, Imphal and Kozhikode are cabled in a triangle, so every office has two ways to every other. Every interface is already addressed. Your job is the routing: use OSPF so every office can reach every other.
Your role: a network engineer on the enterprise team. Level: Beginner Done when: all 7 goals show as passed (70 points).
Network status
Devices: 3 routers, 3 PCs, cabled as drawn. No Layer 1 or Layer 2 faults: every link is connected and up. R-Vizag starts with addresses (G0/0 10.44.1.1/24, G0/1 172.24.24.1/30, G0/2 172.24.24.10/30). PC-Vizag is a host with 10.44.1.10/24, gateway 10.44.1.1. R-Imphal starts with addresses (G0/0 10.44.2.1/24, G0/1 172.24.24.2/30, G0/2 172.24.24.5/30). PC-Imphal is a host with 10.44.2.10/24, gateway 10.44.2.1. R-Kozhikode starts with addresses (G0/0 10.44.3.1/24, G0/1 172.24.24.6/30, G0/2 172.24.24.9/30). PC-Kozhikode is a host with 10.44.3.10/24, gateway 10.44.3.1. Known problems
None: nothing is misconfigured. The routers are simply not finished: the goals list what has to be built. Goals
R-Vizag has 2 OSPF neighbours in FULL (8 pts) R-Imphal has 2 OSPF neighbours in FULL (8 pts) R-Kozhikode has 2 OSPF neighbours in FULL (8 pts) OSPF process 73, area 0, with router-IDs 1.1.1.1 … 3.3.3.3 and passive LAN ports (12 pts) R-Vizag learns 10.44.3.0/24 from the protocol (10 pts) 10.44.1.10 (Vizag) reaches 10.44.3.10 (Kozhikode) (12 pts) 10.44.2.10 (Imphal) reaches 10.44.1.10 (Vizag) (12 pts) The activity, in order
Enable OSPF on each router and advertise its LAN and links; keep LAN ports passive. Why: OSPF routes only flow over a FULL adjacency. If a neighbour is stuck in INIT or EXSTART, compare the two ends’ settings. Verify with: show ip ospf neighbor Read the routing table of every router and compare it with the plan. Why: OSPF routes only flow over a FULL adjacency. If a neighbour is stuck in INIT or EXSTART, compare the two ends’ settings. Verify with: show ip ospf neighbor Ping from each LAN to every other LAN, in both directions. Why: OSPF routes only flow over a FULL adjacency. If a neighbour is stuck in INIT or EXSTART, compare the two ends’ settings. Verify with: show ip ospf neighbor 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: A subnet mask instead of a wildcard mask in a network statement Common mistake: Different area numbers on the two ends of a link Common mistake: Leaving the LAN port active so hellos leak to hosts Why this matters
OSPF routers exchange link-state advertisements and each builds the same map of the area, so a new LAN is found everywhere without touching the other routers. Neighbours form only when area, subnet and timers agree.
What you will be able to do
Enable OSPF with a router-id and network statements
Read neighbour state and the learned routes
Find an area mismatch
The network
ISR 2911, PC — 6 devices in all, already cabled.
Fa0 Gi0/0 10.44.1.1/24 Fa0 Gi0/0 10.44.2.1/24 Fa0 Gi0/0 10.44.3.1/24 Gi0/1 172.24.24.1/30 Gi0/1 172.24.24.2/30 Gi0/2 172.24.24.5/30 Gi0/1 172.24.24.6/30 Gi0/2 172.24.24.9/30 Gi0/2 172.24.24.10/30 R-Vizag PC-Vizag 10.44.1.10/24 · gw 10.44.1.1 R-Imphal PC-Imphal 10.44.2.10/24 · gw 10.44.2.1 R-Kozhikode PC-Kozhikode 10.44.3.10/24 · gw 10.44.3.1 Drawn from this lab: devices, cables, ports and the addresses already set. Device Model Address already set
R-Vizag ISR 2911 configure it PC-Vizag PC 10.44.1.10 / 255.255.255.0 gw 10.44.1.1 R-Imphal ISR 2911 configure it PC-Imphal PC 10.44.2.10 / 255.255.255.0 gw 10.44.2.1 R-Kozhikode ISR 2911 configure it PC-Kozhikode PC 10.44.3.10 / 255.255.255.0 gw 10.44.3.1
Cabling
PC-Vizag Fa0 ↔ R-Vizag Gi0/0 PC-Imphal Fa0 ↔ R-Imphal Gi0/0 PC-Kozhikode Fa0 ↔ R-Kozhikode Gi0/0 R-Vizag Gi0/1 ↔ R-Imphal Gi0/1 R-Imphal Gi0/2 ↔ R-Kozhikode Gi0/1 R-Kozhikode Gi0/2 ↔ R-Vizag 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-Vizag interface g0/0
ip address 10.44.1.1 255.255.255.0
no shutdown
exit
interface g0/1
ip address 172.24.24.1 255.255.255.252
no shutdown
exit
interface g0/2
ip address 172.24.24.10 255.255.255.252
no shutdown
exit R-Imphal interface g0/0
ip address 10.44.2.1 255.255.255.0
no shutdown
exit
interface g0/1
ip address 172.24.24.2 255.255.255.252
no shutdown
exit
interface g0/2
ip address 172.24.24.5 255.255.255.252
no shutdown
exit R-Kozhikode interface g0/0
ip address 10.44.3.1 255.255.255.0
no shutdown
exit
interface g0/1
ip address 172.24.24.6 255.255.255.252
no shutdown
exit
interface g0/2
ip address 172.24.24.9 255.255.255.252
no shutdown
exit 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-Vizag has 2 OSPF neighbours in FULL 8 On R-Vizag: show ip ospf neighbor shows at least 2 neighbour(s) in FULL. 2 R-Imphal has 2 OSPF neighbours in FULL 8 On R-Imphal: show ip ospf neighbor shows at least 2 neighbour(s) in FULL. 3 R-Kozhikode has 2 OSPF neighbours in FULL 8 On R-Kozhikode: show ip ospf neighbor shows at least 2 neighbour(s) in FULL. 4 OSPF process 73, area 0, with router-IDs 1.1.1.1 … 3.3.3.3 and passive LAN ports 12 On R-Vizag: show running-config contains the line(s) matching router ospf 73[\s\S]*router-id 1\.1\.1\.1. and On R-Imphal: show running-config contains the line(s) matching router ospf 73[\s\S]*router-id 2\.2\.2\.2. and On R-Kozhikode: show running-config contains the line(s) matching router ospf 73[\s\S]*router-id 3\.3\.3\.3. 5 R-Vizag learns 10.44.3.0/24 from the protocol 10 On R-Vizag: show ip route lists 10.44.3.0/24. 6 10.44.1.10 (Vizag) reaches 10.44.3.10 (Kozhikode) 12 On PC-Vizag: ping 10.44.3.10 must succeed. 7 10.44.2.10 (Imphal) reaches 10.44.1.10 (Vizag) 12 On PC-Imphal: ping 10.44.1.10 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
A subnet mask instead of a wildcard mask in a network statement
Different area numbers on the two ends of a link
Leaving the LAN port active so hellos leak to hosts
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-Vizag router ospf 73
router-id 1.1.1.1
network 10.44.1.0 0.0.0.255 area 0
network 172.24.24.0 0.0.0.3 area 0
network 172.24.24.8 0.0.0.3 area 0
passive-interface GigabitEthernet0/0
exit R-Imphal router ospf 73
router-id 2.2.2.2
network 10.44.2.0 0.0.0.255 area 0
network 172.24.24.0 0.0.0.3 area 0
network 172.24.24.4 0.0.0.3 area 0
passive-interface GigabitEthernet0/0
exit R-Kozhikode router ospf 73
router-id 3.3.3.3
network 10.44.3.0 0.0.0.255 area 0
network 172.24.24.4 0.0.0.3 area 0
network 172.24.24.8 0.0.0.3 area 0
passive-interface GigabitEthernet0/0
exit Where this is examined
CCNA 3.0 OSPFv2; CCNP ENARSI OSPF.
This lab practises these topics in the zNetLaB certification courses:
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