10 hands-on EIGRP scenarios you build in your own Cisco Modeling Labs instance and grade against the answer key. EIGRP configuration and troubleshooting practice for CCNA and CCNP.
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Advanced EIGRP capstone, run as a fault hunt. The branch LAN has disappeared from the network, one router sees only half its neighbours, and the routing process looks healthy on every device. Nothing was recorded. You get symptoms and the required end state — no fault list. Faults span all three routers, and two of them leave EIGRP running perfectly while doing nothing useful.
Implement classic EIGRP manual summarization on R1 to collapse four contiguous /24 loopback routes into a single /22 summary toward R2, reducing R2’s routing table entries while preserving reachability.
Inject a static default route from an edge router into an EIGRP domain so internal routers and hosts gain internet reachability. You will verify the D*EX 0.0.0.0/0 on the internal router and validate end-to-end connectivity from a branch host through the edge to an ISP-side server.
Build a 3-router EIGRP domain where R1 reaches R3’s loopback over two paths (direct and via R2). You will tune interface delay so the indirect path becomes the successor and the direct path remains a feasible successor, then enable variance to install both unequal-cost paths in R1’s routing table. Two Alpine hosts validate end-to-end reachability while router show commands confirm unequal-cost load sharing.
Build a two-router, two-LAN EIGRP domain and practice precise wildcard-masked network statements so only the intended interfaces participate. R1 has an extra LAN on Ethernet0/2 (172.16.99.0/24) that must be excluded from EIGRP. Validate with show commands and end-host pings that the correct LANs are exchanged and the excluded LAN is not advertised.
Build and verify EIGRP on a small routed topology while marking the user-facing LAN interface as passive. You will advertise the LAN into EIGRP without forming an adjacency on that segment, preventing rogue neighbors and reducing control-plane noise. Focus on deterministic EIGRP configuration, wildcard-based network inclusion, and verification using show commands.
Tune EIGRP path selection by manipulating cumulative delay. Three routers (R1-R2-R3) form EIGRP 100 adjacencies over three /30 point-to-point links. R3 originates 192.168.30.0/24 on Loopback0. You will enable EIGRP and then increase delay on R1’s direct link to R3 so R1 prefers the indirect path via R2 to reach 192.168.30.0/24. Two Alpine hosts validate end-to-end reachability and path choice.
Harden EIGRP adjacencies with MD5 authentication between two iol-xe routers over a /30 transit, then validate that only trusted peers form neighbors. You will configure a key chain, bind it to the transit interface, and enable EIGRP (AS 100) to exchange two user LANs. Verification includes neighbor state, key chain presence, and end-to-end host reachability.
Configure a classic hub-and-spoke EIGRP domain where the single-homed branch (R2) is made an EIGRP stub, limiting query scope while still advertising its LAN. Validate that R1 flags R2 as a stub neighbor, routes still exchange, and query behavior is scoped appropriately.
Bring up EIGRP in AS 100 between two routers over a /30 transit and advertise a single LAN. Verify the first adjacency forms and that R2 learns R1's LAN via EIGRP. Includes realistic end hosts on a shared LAN for path testing.
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EIGRP sits on both the CCNA and CCNP blueprints, and it is still running in a great many all-Cisco enterprise networks, which makes it a protocol you inherit rather than one you choose. The configuration is deceptively short: start a process, advertise some networks, turn off auto-summary. That brevity is the trap. EIGRP fails quietly. A mismatched AS number, a wildcard mask that does not actually cover the interface address, a mismatched K-value set, an interface left passive, or an authentication key that differs by one character all produce the same symptom: no neighbor, no error message, nothing on screen to read. And the parts that separate a CCNA answer from a CCNP one, like the feasibility condition and unequal-cost load balancing, only become concrete once you watch the topology table change in front of you.
These labs run on real Cisco IOS in Cisco Modeling Labs. You bring up router eigrp 100 with matching AS numbers on both ends, advertise interfaces with network statements and correct wildcard masks, set no auto-summary, and confirm the adjacency with show ip eigrp neighbors before trusting anything downstream of it. From there they go deeper: reading feasible distance against reported distance in show ip eigrp topology, checking metric weights and timers with show ip protocols, tuning interface delay to steer a path, enabling unequal-cost load balancing with variance, propagating a default route, manual summarization, and MD5 authentication built from a key chain with ip authentication mode eigrp and ip authentication key-chain eigrp. Break/fix scenarios inject the classic faults, including an AS mismatch, a passive interface swallowing hellos, and a query that leaves a route stuck in active. Upload your CML export and the configuration is graded requirement by requirement against the answer key.
Start with the AS number: the number in router eigrp must be identical on both routers, because unlike an OSPF process ID it is not locally significant. If the AS matches, check show ip protocols for mismatched K-values, confirm the wildcard mask on your network statement actually covers the interface address, and make sure the interface has not been made passive. Mismatched EIGRP authentication is the other common cause. Several labs inject exactly these faults for you to find.
The successor is the neighbor offering the lowest total metric, the feasible distance, to a destination, and its route is what gets installed in the routing table. A feasible successor is a pre-qualified backup: a neighbor whose reported distance to that destination is lower than the current feasible distance, which mathematically rules out a loop. If one exists, DUAL fails over to it immediately. If none exists, the route goes active and EIGRP has to query neighbors, which is where stuck-in-active behavior comes from.
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