EIGRP Routing

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.

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.

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.

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.

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.

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.

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.