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Fix the gateway pair 40 — two routers both think they are active
Enterprise Advanced 4 devices 4 checked tasks 100 points Plan lab
Scenario — Cuttack runs HSRP on R1 and R2 for the gateway 10.59.0.254, but users report duplicate-address warnings and flapping. R1 uses group 40 and R2 was typed into group 41 with the same virtual address, so both claim to be active. Put R2 into the same group as R1, keep R1 active (priority 119, with preempt) and prove the PC still reaches the gateway. 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.
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The scenario
Cuttack runs HSRP on R1 and R2 for the gateway 10.59.0.254, but users report duplicate-address warnings and flapping. R1 uses group 40 and R2 was typed into group 41 with the same virtual address, so both claim to be active. Put R2 into the same group as R1, keep R1 active (priority 119, with preempt) and prove the PC still reaches the gateway.
Your role: a network engineer on the enterprise team. Level: Advanced Done when: all 4 goals show as passed (100 points).
Network status
Devices: 2 routers, 1 switch, 1 PC, cabled as drawn. No Layer 1 or Layer 2 faults: every link is connected and up. R1 starts with addresses (G0/0 10.59.0.1/24) and HSRP already configured. R2 starts with addresses (G0/0 10.59.0.2/24) and HSRP already configured. PC is a host with 10.59.0.50/24, gateway 10.59.0.254. SW starts with an empty configuration. Known problems
The network worked and now does not: the scenario above says what users report. The cause is a configuration fault, not a cable. Find it with show commands (interfaces, routes, neighbours, running-config) before you change anything; fix only what is wrong. Goals
R1 is the active router of group 40 (25 pts) R2 is standing by in the same group (35 pts) R2 no longer carries the stray group 41 (20 pts) The PC reaches the virtual gateway (20 pts) The activity, in order
R1 is the active router of group 40 Why: Hosts point at the virtual IP, so when the active router dies the standby answers and nobody reconfigures anything. Verify with: show standby brief R2 is standing by in the same group Why: The standby is the one that takes over; it must be configured identically except for priority. Verify with: show standby brief R2 no longer carries the stray group 41 Why: Reading a show command is the core skill of troubleshooting: the output is the truth, not your configuration. Verify with: show running-config The PC reaches the virtual gateway Why: A ping needs a route in BOTH directions. This is the end-to-end proof that everything before it worked. Verify with: ping 10.59.0.254 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: Changing the VIP instead of the group Common mistake: Leaving the old group configured Common mistake: Forgetting preempt on the intended active router Why this matters
HSRP routers only cooperate inside one group number. Two routers in different groups with the same virtual IP each elect themselves active, so two devices answer for one address — the classic copy-and-paste error.
What you will be able to do
Read show standby on both routers
Spot a group-number mismatch
Re-join a router to the right group
The network
ISR 2911, Catalyst 2960-24TT, PC — 4 devices in all, already cabled.
Fa0/1 Fa0 Fa0/2 Gi0/0 10.59.0.1/24 Fa0/3 Gi0/0 10.59.0.2/24 R1 R2 SW PC 10.59.0.50/24 · gw 10.59.0.254 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 SW Catalyst 2960-24TT configure it PC PC 10.59.0.50 / 255.255.255.0 gw 10.59.0.254
Cabling
SW Fa0/1 ↔ PC Fa0 SW Fa0/2 ↔ R1 Gi0/0 SW Fa0/3 ↔ R2 Gi0/0
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 10.59.0.1 255.255.255.0
no shutdown
exit
interface g0/0
standby 40 ip 10.59.0.254
standby 40 priority 119
standby 40 preempt
exit R2 interface g0/0
ip address 10.59.0.2 255.255.255.0
no shutdown
exit
interface g0/0
standby 41 ip 10.59.0.254
standby 41 priority 100
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 active router of group 40 25 On R1: show standby brief — the router is Active. 2 R2 is standing by in the same group 35 On R2: show standby brief — the router is Standby. 3 R2 no longer carries the stray group 41 20 On R2: show running-config output matches standby 41 — it must not . 4 The PC reaches the virtual gateway 20 On PC: ping 10.59.0.254 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
Changing the VIP instead of the group
Leaving the old group configured
Forgetting preempt on the intended active router
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:
R2 interface g0/0
no standby 41 ip 10.59.0.254
no standby 41 priority 100
standby 40 ip 10.59.0.254
standby 40 priority 100
exit Where this is examined
CCNA 3.0 FHRP; CCNP ENCOR HSRP.
This lab practises these topics in the zNetLaB certification courses:
Related labs
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