Advanced EIGRP Practice Questions

Answers and explanations appear when you work through the set above.

1. The current EIGRP successor's feasible distance to a prefix is 42,000. A candidate neighbor reports a distance of 44,000 for that same prefix. Can this neighbor become a feasible successor?

   • Yes, since any finite reported distance satisfies the feasibility condition
   • No, because the neighbor's reported distance (44,000) is not lower than the current feasible distance (42,000), so it fails the feasibility condition and is not guaranteed loop-free
   • Yes, but only if the resulting total distance is also lower than 42,000
   • It depends on whether the neighbor is a stub router

2. Two directly connected EIGRP routers on the same subnet exchange hello packets visibly in a packet capture, but no neighbor adjacency ever forms. `show ip protocols` reveals that the two routers have different K-value configurations. What fixes this?

   • Match the K values on both routers, since EIGRP requires identical K-value sets to form a neighbor relationship
   • Configure next-hop-self on both routers
   • Change the OSPF network type to point-to-point
   • Disable EIGRP split horizon on the shared interface

3. A hub-and-spoke EIGRP topology suffers from extensive query propagation and slow convergence whenever a spoke's link flaps. The spokes never act as transit paths for each other. Which change most directly limits the query scope causing this?

   • Configure the spoke routers as EIGRP stubs
   • Increase the variance value at the hub
   • Turn off summarization everywhere in the topology
   • Lower the administrative distance of EIGRP on the spokes

4. Loopback0 is included in the EIGRP network statement and additionally configured as a passive interface. What is the resulting behavior?

   • The loopback prefix stops being advertised entirely
   • The loopback's prefix can still be advertised in EIGRP updates, but no EIGRP hello packets are sent or accepted on that interface, so no neighbor relationship can form there
   • The interface continues sending hellos but silently drops any incoming updates
   • The interface automatically becomes an EIGRP stub

5. R1's EIGRP successor metric to a destination is 1,000, and its best feasible successor has a metric of 1,700. Assuming maximum-paths permits it, what is the smallest integer variance multiplier that makes this feasible successor eligible for unequal-cost load balancing?

   • 1
   • 2
   • 3
   • 4

6. An EIGRP prefix is present in the topology table on one router but is missing specifically when learned through interface Gi0/1. Which command gives the fastest overview of any inbound or outbound distribute-list filtering tied to the EIGRP process?

   • show ip protocols
   • show spanning-tree
   • show arp
   • show crypto ikev2 sa

7. A branch WAN link carries dozens of individual EIGRP prefixes toward the core. The design goal is to keep the core's routing table stable and avoid the core generating queries down to the branch for every internal branch-side change. Which combination of features best meets both goals?

   • Interface-level route summarization toward the core, combined with stub configuration at the branch
   • Variance plus passive-interface on the WAN link
   • Redistribute connected combined with disabling split horizon
   • Changing K values and enabling BFD alone

8. In EIGRP named configuration mode, under which context are topology-wide settings such as redistribution and variance configured, as opposed to per-interface settings?

   • Under the address-family topology base (or a named topology) submode
   • Only directly under each physical interface, with no process-level context
   • Under router ospf, since named EIGRP reuses OSPF's configuration hierarchy
   • In line configuration mode

9. Two directly connected routers with up/up interfaces are configured for EIGRP but with different autonomous-system numbers on the router eigrp command. What is the expected result?

   • They will still form a neighbor relationship because AS numbers are only used for redistribution filtering
   • They do not form an EIGRP neighbor adjacency, because the classic router eigrp <as-number> command requires both sides to use a matching AS number
   • DUAL is disabled on both routers automatically
   • One router is automatically elected as a designated router

10. A router remains in the Active state for a route because it does not receive a reply to an EIGRP query from one or more neighbors within the expected time. What condition is this router at risk of entering?

    • Passive state, which is the normal stable condition
    • Stuck-in-Active (SIA), where the router eventually resets the neighbor relationship with the non-responding neighbor if the active timer expires
    • An automatic transition to OSPF DR
    • A permanent hold in the Init neighbor state

11. A spoke router in a hub-and-spoke frame relay or DMVPN design learns a route via the hub, but the hub also needs to advertise that same route back out to a different spoke over the same physical or logical interface it was learned on. Which mechanism most directly affects whether that re-advertisement happens by default?

    • Split horizon, which by default suppresses re-advertising a route out the same interface it was learned on
    • The route is always placed permanently in Active state
    • DUAL is automatically disabled on multipoint interfaces
    • The interface automatically becomes an OSPF DR

12. All EIGRP parameters between two candidate neighbors match except that one side has authentication configured and the other does not. What is the expected symptom?

    • The neighbor relationship still forms normally because authentication is optional per-packet
    • The two routers fail to establish a valid EIGRP neighbor relationship, since authentication settings must agree on both sides of the link
    • DUAL disables itself on the side with authentication enabled
    • The interface with authentication automatically becomes passive

13. Which default hello interval applies to EIGRP interfaces with bandwidth greater than T1 speed (above 1.544 Mbps), such as typical Ethernet links?

    • 5 seconds
    • 10 seconds
    • 30 seconds
    • 60 seconds

14. Which default hello interval applies to EIGRP on low-speed, multipoint, non-broadcast interfaces such as classic Frame Relay multipoint subinterfaces at or below T1 speed?

    • 5 seconds
    • 10 seconds
    • 30 seconds
    • 60 seconds

15. In the EIGRP topology table, what state name describes a route that is stable and not currently undergoing DUAL recomputation?

    • Active
    • Query-pending
    • Passive
    • Stuck

16. Which command gives the fastest confirmation of which IPv4 EIGRP neighbors have actually completed adjacency formation?

    • show ip eigrp topology
    • show ip eigrp neighbors
    • show ip protocols
    • show ip eigrp traffic

17. Which command provides interface-level EIGRP detail, including configured authentication, split-horizon state, and hello/hold timers for a specific interface?

    • show ip eigrp interfaces detail
    • show ip route eigrp
    • show ip eigrp events
    • show ip eigrp accounting

18. What is the main operational benefit of configuring interface-level route summarization at a WAN boundary in an EIGRP network?

    • It forces all traffic through the interface toward a default route
    • It reduces the number of specific routes advertised across the boundary and can also reduce the scope of EIGRP queries that need to propagate across it
    • It automatically disables DUAL on the summarizing interface
    • It converts internal EIGRP routes into external EIGRP routes

19. Which interface characteristic, adjustable with an IOS interface command, is commonly tuned to influence EIGRP path selection without changing the physical bandwidth value used by other calculations such as QoS?

    • Interface delay, via the delay command, since EIGRP's composite metric weighs cumulative delay along with bandwidth
    • OSPF interface cost
    • The interface's configured MTU
    • The interface's duplex setting

20. An EIGRP summary route is configured on an interface, and every component subnet covered by that summary is currently up and present in the topology table. Why might a discard route to Null0 for the summary still appear in the local routing table?

    • To force all summarized traffic to use a configured default route instead
    • To safely drop traffic addressed to a portion of the summarized range that does not correspond to any actual, more-specific component subnet, preventing a potential routing loop
    • To trigger EIGRP queries for each component prefix on every topology change
    • To convert the summary route into an externally tagged EIGRP route

21. R1's EIGRP successor metric is 1,200, and its best feasible successor's metric is 2,500, with variance 2 configured and maximum-paths allowing more than one path. Is the feasible successor eligible for unequal-cost load balancing?

    • Yes, because any finite alternate metric qualifies once variance is configured at all
    • No, because 2,500 exceeds 2 times the successor metric of 1,200 (which is 2,400), so it fails the variance test
    • Yes, because 2,500 is less than 3 times the successor metric
    • It depends only on whether the alternate is externally tagged

22. A network engineer wants an EIGRP router at a branch office to accept routes from the hub and forward traffic normally, but never be queried by the hub for alternate paths and never advertise routes learned from one hub-facing neighbor to another. Which single feature accomplishes all of this most directly?

    • The eigrp stub command with default connected and summary keywords
    • A distribute list applied only outbound
    • A higher administrative distance configured for EIGRP
    • Disabling split horizon on the branch's WAN interface

23. Two EIGRP neighbors in classic (non-named) configuration mode are both configured for MD5 authentication, but one router's key-chain has the key configured with a mismatched key string. What is the most likely symptom?

    • The adjacency forms normally since only the key-chain name needs to match
    • The routers fail to authenticate each other's hello packets and do not form a stable neighbor relationship
    • EIGRP falls back automatically to cleartext authentication
    • The mismatch only affects redistributed routes, not the neighbor relationship itself

24. In EIGRP named configuration mode, which top-level command begins the configuration block, distinguishing it from the classic autonomous-system-number style?

    • router eigrp <process-name>, followed by an address-family statement that specifies the AS number
    • router eigrp <as-number> only, with no further nesting
    • eigrp router-id <process-name>
    • ip eigrp <process-name> under global configuration