CCNA EIGRP interview questions focus on neighbor relationships, route calculation, metrics, and loop-free backup paths. These answers provide a modern foundation for discussion and lab practice.
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What is EIGRP?
Enhanced Interior Gateway Routing Protocol exchanges routing information between neighbors and uses the Diffusing Update Algorithm to select loop-free paths.
What tables does EIGRP maintain?
It maintains a neighbor table, a topology table containing learned paths, and routes installed in the routing table.
What is a successor?
The successor is the best loop-free path to a destination and is installed in the routing table.
What is a feasible successor?
A feasible successor is a loop-free backup path that satisfies the feasibility condition. It can support rapid convergence if the successor fails.
What metric does EIGRP use?
By default, the composite metric uses bandwidth and delay. Reliability and load can be included through K-values, but changing those values is uncommon and must match between neighbors.
How do neighbors form?
EIGRP neighbors exchange Hello packets and require compatible autonomous-system settings, K-values, and addressing. Authentication settings must also match when configured.
Does EIGRP send full updates?
After initial exchange, EIGRP normally sends partial, bounded updates when information changes rather than regularly transmitting the entire routing table.
What is unequal-cost load balancing?
EIGRP can install multiple unequal-cost paths when the variance configuration and feasibility conditions permit them.
Which commands troubleshoot EIGRP?
Use show ip eigrp neighbors, show ip eigrp topology, show ip protocols, and show ip route eigrp.
Common Failure Checks
Verify addressing, interface state, autonomous-system configuration, passive interfaces, ACLs, authentication, K-values, and whether the expected network is included.