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EIGRP summarisation on the interface
Enterprise Advanced 2 devices 3 checked tasks 100 points Plan lab
A branch advertises four /24 loopbacks into EIGRP and the hub carries all four. Summarise them to one /22 on the branch’s uplink with ip summary-address, and watch the specifics leave the hub’s table while the summary arrives with a discard route behind it on the branch. 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
A branch advertises four /24 loopbacks into EIGRP and the hub carries all four. Summarise them to one /22 on the branch’s uplink with ip summary-address, and watch the specifics leave the hub’s table while the summary arrives with a discard route behind it on the branch.
Your role: a network engineer on the enterprise team. Level: Advanced Done when: all 3 goals show as passed (100 points).
Network status
Devices: 2 routers, cabled as drawn. No Layer 1 or Layer 2 faults: every link is connected and up. Branch starts with addresses (G0/1 10.0.12.1/30, L1 172.16.0.1/24, L2 172.16.1.1/24, L3 172.16.2.1/24, L4 172.16.3.1/24) and EIGRP 100 already configured. Hub starts with addresses (G0/1 10.0.12.2/30) and EIGRP 100 already configured. 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
The branch summarises toward the hub on its uplink (40 pts) The hub has the summary 172.16.0.0/22 (35 pts) The hub no longer carries the specific /24s (25 pts) The activity, in order
The branch summarises toward the hub on its uplink Why: This is the task that checks your configuration directly: the line must really be there, not just look right. Verify with: show running-config The hub has the summary 172.16.0.0/22 Why: If the prefix is not in the routing table, the router drops packets for it, whatever else is configured. Verify with: show ip route The hub no longer carries the specific /24s Why: A route that should not exist is a leak or a loop waiting to happen. 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. Common mistake: Using auto-summary instead (classful boundaries) Common mistake: Applying it on the wrong interface Common mistake: Expecting the summary on the originating router’s own table to disappear Why this matters
EIGRP summarisation is configured per interface, not per process, and it limits the query scope as well as the table size — one of the reasons large EIGRP networks stay stable.
What you will be able to do
Summarise toward a neighbour with ip summary-address eigrp
Verify the summary appears and the specifics do not
Explain the discard route created for the summary
The network
ISR 2911 — 2 devices in all, already cabled.
Gi0/1 10.0.12.1/30 Gi0/1 10.0.12.2/30 Branch Hub Drawn from this lab: devices, cables, ports and the addresses already set. Device Model Address already set
Branch ISR 2911 configure it Hub ISR 2911 configure it
Cabling
Branch Gi0/1 ↔ Hub 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:
Branch interface g0/1
ip address 10.0.12.1 255.255.255.252
no shutdown
exit
interface lo1
ip address 172.16.0.1 255.255.255.0
no shutdown
exit
interface lo2
ip address 172.16.1.1 255.255.255.0
no shutdown
exit
interface lo3
ip address 172.16.2.1 255.255.255.0
no shutdown
exit
interface lo4
ip address 172.16.3.1 255.255.255.0
no shutdown
exit
router eigrp 100
network 10.0.12.0 0.0.0.3
network 172.16.0.0 0.0.3.255
no auto-summary Hub interface g0/1
ip address 10.0.12.2 255.255.255.252
no shutdown
exit
router eigrp 100
network 10.0.12.0 0.0.0.3
no auto-summary 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 The branch summarises toward the hub on its uplink 40 On Branch: show running-config contains the line(s) matching ip summary-address eigrp 100 172\.16\.0\.0 255\.255\.252\.0. 2 The hub has the summary 172.16.0.0/22 35 On Hub: show ip route lists 172.16.0.0/22. 3 The hub no longer carries the specific /24s 25 On Hub: show ip route does not list 172.16.2.0/24.
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
Using auto-summary instead (classful boundaries)
Applying it on the wrong interface
Expecting the summary on the originating router’s own table to disappear
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:
Branch interface g0/1
ip summary-address eigrp 100 172.16.0.0 255.255.252.0
exit Where this is examined
CCNP ENCOR/ENARSI (EIGRP), CCIE EI.
This lab practises these topics in the zNetLaB certification courses:
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Where to start
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