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Multi-area OSPF and the DR election
Enterprise Intermediate 5 devices 4 checked tasks 100 points Plan lab
Three routers share a LAN in area 0, and R3 is also the way into area 1. Make R1 the DR by priority, keep R2 out of the election altogether, and watch area 1 arrive in the backbone as inter-area routes — and the backbone in area 1. 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
Three routers share a LAN in area 0, and R3 is also the way into area 1. Make R1 the DR by priority, keep R2 out of the election altogether, and watch area 1 arrive in the backbone as inter-area routes — and the backbone in area 1.
Your role: a network engineer on the enterprise team. Level: Intermediate Done when: all 4 goals show as passed (100 points).
Network status
Devices: 4 routers, 1 switch, cabled as drawn. No Layer 1 or Layer 2 faults: every link is connected and up. R1 starts with addresses (G0/0 10.0.123.1/24, L0 1.1.1.1/32). R2 starts with addresses (G0/0 10.0.123.2/24). R3-ABR starts with addresses (G0/0 10.0.123.3/24, G0/1 10.0.34.3/24). R4 starts with addresses (G0/1 10.0.34.4/24, L0 4.4.4.4/32). SW-Core starts with an empty configuration. Known problems
None: nothing is misconfigured. The network is simply not finished: what the goals list is what you have to build or secure. Goals
R1 is the DR on the shared LAN (25 pts) R1 is adjacent to both other routers on the LAN (20 pts) R4 learns the backbone LAN as an inter-area route (30 pts) R1 learns R4’s loopback from area 1 as O IA (25 pts) The activity, in order
R1 is the DR on the shared LAN Why: The DR is the router every other router on a LAN talks to, so which one it is matters. Verify with: show ip ospf neighbor R1 is adjacent to both other routers on the LAN 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 R4 learns the backbone LAN as an inter-area route Why: The code tells you HOW a route was learned, which tells you which process to look at if it is wrong. Verify with: show ip route R1 learns R4’s loopback from area 1 as O IA Why: The code tells you HOW a route was learned, which tells you which process to look at if it is wrong. Verify with: show ip route 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. Why this matters
Three routers share a LAN in area 0, and R3 is also the way into area 1. Make R1 the DR by priority, keep R2 out of the election altogether, and watch area 1 arrive in the backbone as inter-area routes — and the backbone in area 1.
What you will be able to do
R1 is the DR on the shared LAN
R1 is adjacent to both other routers on the LAN
R4 learns the backbone LAN as an inter-area route
R1 learns R4’s loopback from area 1 as O IA
The network
ISR 2911, Catalyst 2960-24TT — 5 devices in all, already cabled.
Gi0/0 10.0.123.1/24 Fa0/1 Gi0/0 10.0.123.2/24 Fa0/2 Gi0/0 10.0.123.3/24 Fa0/3 Gi0/1 10.0.34.3/24 Gi0/1 10.0.34.4/24 R1 R2 R3-ABR R4 SW-Core Drawn from this lab: devices, cables, ports and the addresses already set. Device Model Address already set
R1 ISR 2911 configure it R2 ISR 2911 configure it R3-ABR ISR 2911 configure it R4 ISR 2911 configure it SW-Core Catalyst 2960-24TT configure it
Cabling
R1 Gi0/0 ↔ SW-Core Fa0/1 R2 Gi0/0 ↔ SW-Core Fa0/2 R3-ABR Gi0/0 ↔ SW-Core Fa0/3 R3-ABR Gi0/1 ↔ R4 Gi0/1
What is configured at the start
These are already configured when the lab opens — including, where this is a troubleshooting lab, the fault itself:
R1 interface g0/0
ip address 10.0.123.1 255.255.255.0
no shutdown
exit
interface lo0
ip address 1.1.1.1 255.255.255.255
no shutdown
exit R2 interface g0/0
ip address 10.0.123.2 255.255.255.0
no shutdown
exit R3-ABR interface g0/0
ip address 10.0.123.3 255.255.255.0
no shutdown
exit
interface g0/1
ip address 10.0.34.3 255.255.255.0
no shutdown
exit R4 interface g0/1
ip address 10.0.34.4 255.255.255.0
no shutdown
exit
interface lo0
ip address 4.4.4.4 255.255.255.255
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 R1 is the DR on the shared LAN 25 Checked automatically against the device’s live state (ospfDr). 2 R1 is adjacent to both other routers on the LAN 20 On R1: show ip ospf neighbor shows at least 2 neighbour(s) in FULL. 3 R4 learns the backbone LAN as an inter-area route 30 On R4: show ip route lists 10.0.123.0/24 with code O IA. 4 R1 learns R4’s loopback from area 1 as O IA 25 On R1: show ip route lists 4.4.4.4/32 with code O IA.
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
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:
R1 interface g0/0
ip ospf priority 200
exit
router ospf 1
router-id 1.1.1.1
network 10.0.123.0 0.0.0.255 area 0
network 1.1.1.1 0.0.0.0 area 0 R2 interface g0/0
ip ospf priority 0
exit
router ospf 1
router-id 2.2.2.2
network 10.0.123.0 0.0.0.255 area 0 R3-ABR router ospf 1
router-id 3.3.3.3
network 10.0.123.0 0.0.0.255 area 0
network 10.0.34.0 0.0.0.255 area 1 R4 router ospf 1
router-id 4.4.4.4
network 10.0.34.0 0.0.0.255 area 1
network 4.4.4.4 0.0.0.0 area 1 Where this is examined
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