1. Which transport layer protocol is used for exchange of EIGRP messages?
- TCP
- RSVP
- UDP
- EIGRP runs directly above the network layer and does not use additional transport protocols.
- RTP
Explanation: Topic 1.3.0
EIGRP uses the Reliable Transport Protocol (RTP) to ensure the guaranteed and ordered delivery of its packets (such as Updates and Queries). It operates directly above the network layer using IP protocol number 88.
2. Which of the following would cause the router to go active on a route?
- The router receives an update containing information about a new prefix.
- Border routers join the inactive route.
- The EIGPR topology table refresh timer expires.
- A route is lost but the router has no feasible successor available.
Explanation: Topic 2.2.0
A router transitions to the active state for a specific route when that route is lost and the topology table contains no feasible successor to provide an immediate alternative path. This triggers the router to send Queries to neighbors to find a new path.
3. You plan to configure a summary route with the ip summary-address eigrp command. Which of the following, when added to such a command, would create a summary that includes all four of the following subnets: 10.1.100.0/25, 10.1.101.96/27, 10.1.101.224/28, and 10.1.100.128/25?
- 10.1.64.0 255.255.192.0
- 10.1.0.0 255.255.192.0
- 10.1.100.0 255.255.255.0
- 10.1.98.0 255.255.252.0
Explanation: Topic 2.6.4
To summarize subnets in 10.1.100.x and 10.1.101.x, the summary must encompass the third-octet range of at least 100–101. 10.1.64.0/18 (255.255.192.0) covers the range from 10.1.64.0 to 10.1.127.255, making it the only provided option that successfully includes all four specified subnets.
4. What does the passive state in the EIGRP topology table signify?
- The network is unreachable.
- A feasible successor has been selected.
- The network is up and operational, and conditions are normal.
- There are outstanding queries for this network.
Explanation: Topic 1.8.2
In the EIGRP topology table, the passive (P) state is the normal, desirable state signifying that the network is fully converged and the DUAL algorithm is not actively recalculating a path for that prefix. Conversely, the active (A) state indicates that a route is being recomputed.
5. Which EIGRP table contains a list of FD and RD for all networks learned from each neighbor?
- EIGRP protocol table
- EIGRP routing table
- EIGRP neighbor table
- EIGRP topology table
Explanation: Topic 1.8.2
The EIGRP topology table is the data structure that stores all destination routes learned from neighbors, including their Reported Distance (RD) and the locally calculated Feasible Distance (FD).
6. Which packet type establishes neighbor relationships?
- reply
- hello
- update
- ACK
- query
Explanation: Topic 1.8.1
EIGRP uses Hello packets to discover neighbors on a link and to dynamically establish and maintain neighbor relationships (adjacencies).
7. Which EIGRP feature limits Query message scope in a network to improve network stability and reduce resource utilization?
- Stub routing
- Named configuration
- Route summarization
- Query suppression
Explanation: Topic 2.3.0
Stub routing improves network stability by limiting the scope of Query messages; non-stub routers are instructed not to send Queries to routers configured as stubs.
8. When implementing EIGRP unequal cost load balancing using the variance command, which two conditions must be met? (Choose two.)
- The router must be configured with the stub command.
- The metric of the route must be equal to or greater than the metric of the successor, multiplied by the value of the variance.
- The metric of the route must be lower than the metric of the successor, multiplied by the value of the variance.
- The route must be reachable.
- The route must be loop free, by meeting the feasibility condition.
Explanation: Topic 2.9.2
For a route to be used in unequal cost load balancing, it must be a feasible successor (satisfying the feasibility condition to ensure it is loop-free) and its metric must be less than the successor's metric multiplied by the variance.
9. Which verification command shows you the presence or absence of EIGRP peers?
- show ip eigrp traffic
- show ip eigrp neighbors
- show ip eigrp topology
- show ip eigrp timers
Explanation: Topic 1.6.3
The show ip eigrp neighbors command is used to verify the existence of EIGRP peers by displaying the neighbor table, which lists all currently established adjacencies.
10. Which verification command shows you if there are any interfaces that are configured as passive?
- show ip interface
- show ip protocols
- show ip route
- show ip eigrp interfaces
Explanation: Topic 3.4.4
The show ip protocols command (and show ipv6 protocols) displays global protocol information, including a specific section listing all interfaces currently configured as passive.
11. Which IOS command can be used to display the calculated vector metrics of bandwidth, delay, load and reliability?
- show ip eigrp topology 192.168.10.0 255.255.255.0
- show interfaces
- show ip protocols
- show ip eigrp interfaces
Explanation: Topic 1.10.0
Using the show ip eigrp topology <prefix> <mask> command allows you to view the specific vector metrics (minimum bandwidth, total delay, reliability, and load) used by DUAL to calculate the composite metric for that particular destination.
12. The following message appears after the debug eigrp packets command has been enabled: EIGRP: Fa0/0: ignored packet from 10.1.12.2, opcode = 5 (invalid authentication) What would cause this message to appear?
- The network mask on interface F0/0 does not match between the EIGRP neighbors.
- The authentication type does not match between the EIGRP neighbors.
- The AS number does not match between the EIGRP neighbors.
- The authentication key or string does not match between the EIGRP neighbors.
Explanation: Topic 3.9.0
In EIGRP packet debugging, the message "(invalid authentication)" specifically indicates that while authentication is configured on both sides, there is a mismatch in the key ID or the key string (password) being used.
13. Which verification command lets you see if automatic summarization is enabled or disabled?
- show ip protocols
- show ip eigrp interfaces
- show ip route
- show ip eigrp topology
Explanation: Topic 3.5.2
The show ip protocols command provides a summary of the EIGRP process, which explicitly includes the status of Automatic Summarization (enabled or disabled).
14. Which verification command shows you the feasible distance of all received EIGRP IPv6 routes?
- show ipv6 route
- show ipv6 route eigrp
- show ipv6 eigrp
- show ip protocols
- show ipv6 eigrp topology
- show ip eigrp neighbors
Explanation: Topic 3.8.0
The show ipv6 eigrp topology command displays the EIGRP IPv6 topology table, which contains all learned prefixes along with their locally calculated Feasible Distance (FD) and the Reported Distance (RD) from neighbors.
15. What is the formula for selecting a feasible successor?
- The RD of the feasible successor route is less than the FD of the current successor route.
- The RD of the current successor route is less than the FD of the feasible successor route.
- The FD of the feasible successor route is less than the RD of the current successor route.
- The FD of the current successor route is less than the RD of the feasible successor route.
Explanation: Topic 1.12.0
To be considered a feasible successor, a backup route must satisfy the feasibility condition, which states that its Reported Distance (RD) must be strictly lower than the Feasible Distance (FD) of the current successor route. This ensures the backup path is not part of a routing loop.
16. What are two benefits of using named EIGRP configuration? (Choose two.)
- gathering all EIGRP configuration in one place
- improved convergence
- faster convergence
- unifying IPv4 and IPv6 configuration commands
- support for multiple areas
Explanation: Topic 1.5.0
EIGRP named mode was introduced to eliminate the complexity of classic mode by gathering all EIGRP configurations (IPv4 and IPv6) into a single virtual instance. It uses unified configuration commands across different address families, reducing the chance of configuration errors.
17. Which two statements are true regarding EIGRP authentication using a pre-shared key to generate an MD5 digest? (Choose two.)
- EIGRP authentication prevents attackers from establishing a neighbor relationship with a legitimate router.
- The key chain is referenced using the ip authentication key-chain command in global configuration.
- EIGRP authentication helps prevent Denial of Service (DoS) attacks.
- The MD5 hashing algorithm is the only option available for use with EIGRP authentication.
- EIGRP authenticates all EIGRP packets.
Explanation: Topic 2.8.0
When authentication is enabled, every packet exchanged between neighbors is authenticated to verify the neighbor's identity. This prevents unauthorized or malicious routers from forming adjacencies with legitimate routers. Note that the key chain is referenced in interface configuration mode (classic) or af-interface mode (named), not global configuration.
18. Routers R1 and R2 are EIGRP neighbors. R1 has been configured with the eigrp stub connected command. Which two of the following are true as a result? (Choose two.)
- R1 can learn EIGRP routes from R2, but R2 cannot learn EIGRP routes from R1.
- R2 no longer learns EIGRP routes from R1 for routes not connected to R1.
- R1 no longer replies to R2's Query messages.
- R2 no longer sends to R1 Query messages.
- R1 can send IP packets to R2, but R2 cannot send IP packets to R1.
Explanation: Topic 2.3.0
A router configured as a stub (specifically with the connected keyword) will only advertise its directly connected routes that match a network statement; it will not forward routes learned from other EIGRP neighbors. Additionally, non-stub routers (R2) are optimized to stop sending Query messages to stub routers (R1) because the stub is not a transit path.
19. What delay value is used in the EIGRP metric calculation?
- tens of microseconds
- seconds
- milliseconds
- microseconds
Explanation: Topic 1.10.1
In EIGRP classic metric calculations, the delay value used in the formula is the sum of delays along the path expressed in tens of microseconds, even though the show interfaces command displays delay in microseconds.
20. EIGRP for IPv6 uses which multicast address?
- FF02::5
- FF01::10
- FF02::A
- FF01::2
Explanation: Topic 1.3.0
EIGRP for IPv6 uses the reserved link-local multicast address FF02::A to send hello packets and other multicasted routing information. (This corresponds to the IPv4 multicast address 224.0.0.10).
21. Which two of the following are used in EIGRP metric calculations by default? (Choose two.)
- load
- bandwidth
- delay
- MTU
- reliability
- hop count
Explanation: Topic 1.9.0
By default, EIGRP uses only bandwidth (the minimum bandwidth along the path) and delay (the cumulative latency) to calculate its composite metric. Although reliability, load, and MTU are tracked, they are not used in the default metric calculation because the default K-values for these parameters are set to zero.
22. Which two solutions are used in an EIGRP network to reduce DUAL computations? (Choose two.)
- EIGRP stub routing
- summarization
- partial updates
- authentication
- load balancing
Explanation: Topic 2.2.0
EIGRP stub routing and summarization are the two primary methods used to limit the scope of Query messages. By bounding the query propagation, these features prevent routers from unnecessarily engaging the DUAL algorithm to find alternative paths, thereby reducing resource utilization and improving network stability.
23. In an EIGRP network, where can summarization be applied?
- Any EIGRP router can perform summarization.
- Only EIGRP area border routers can perform summarization.
- Only EIGRP autonomous system border routers can perform summarization.
- Only EIGRP stub routers can perform summarization.
Explanation: Topic 2.5.0
EIGRP is highly flexible and supports manual route summarization on any interface of any router within the autonomous system. This distinguishes it from protocols like OSPF, which restrict summarization to specific roles like Area Border Routers (ABR) or Autonomous System Border Routers (ASBR).
24. EIGRP using named mode configuration supports which metric format?
- 32-bit
- 128-bit
- 16-bit
- 64-bit
Explanation: Topic 1.5.0
EIGRP named mode introduced "Wide Metrics," which utilize a 64-bit metric format. This expanded format allows the protocol to perform more accurate calculations for modern high-speed links exceeding 1 Gbps, whereas classic mode is limited to a 32-bit format.
