CCNA Eigrp Questions

The output shows that for 10.1.1.0/24, the feasible distance (FD) is 1310720 and there is only one successor (the route via 192.168.1.2). The alternate path via 10.2.2.2 has a reported distance (RD) of 1310720, which equals the FD, so it does not satisfy the feasibility condition (RD < FD) and therefore is not a feasible successor. Only the successor route is installed in the routing table.

The EIGRP address-family configuration for VRF RED is missing the 'no shutdown' command under the address-family mode. In Cisco IOS, EIGRP address-families are administratively shut down by default; without 'no shutdown', the EIGRP process for that VRF will not form adjacencies or advertise routes, even though the network command is correctly configured.

K1 corresponds to bandwidth, K2 to load, K3 to delay, and K4 to reliability. K5 is not directly assigned to a single metric component; it is a multiplier used with reliability in the metric formula. MTU is not a K variable; it is only used in the feasibility condition.

EIGRP uses a metric based on bandwidth and delay, but it also has a hop count limit. The default maximum hop count is 100, but it can be configured up to 255.

The correct order ensures that the spoke router first enters EIGRP configuration, then configures the stub feature, optionally restricts stub types, and finally applies the configuration. The hub router does not need stub configuration.

EIGRP named mode uses a hierarchical configuration under a single router process, supporting address families (IPv4, IPv6) and VRFs. It simplifies configuration and allows per-interface settings.

EIGRP uses a maximum hop count of 255 to prevent routing loops, as defined in RFC 7868. This is a hard-coded limit in the protocol, and routes with a hop count exceeding 255 are considered unreachable.

EIGRP named mode uses an address-family configuration. First, create the named EIGRP instance, then enter address-family IPv4, configure the network, optionally adjust timers, and finally verify the configuration.

EIGRP uses a maximum hop count of 100 by default to prevent routing loops. This is a hard limit; if a route's hop count exceeds 100, EIGRP considers it unreachable. This value is configurable via the 'metric maximum-hops' command under the EIGRP process.

Redistribution requires enabling redistribution, setting a seed metric (or using default-metric), optionally matching routes, and then verifying. The order ensures routes are properly injected.

The `ip summary-address eigrp TEST 10.0.0.0 255.0.0.0 5` command creates a summary route of 10.0.0.0/8 with an administrative distance of 5, which is advertised out of GigabitEthernet0/0. The EIGRP process name TEST matches the router eigrp configuration, and the summary is generated regardless of the network statements, as long as the router has a more specific route within the summarized range.

In hub-and-spoke EIGRP, the spoke router is configured as a stub to limit query propagation. First, enter router configuration mode, then enable EIGRP on the spoke, configure it as a stub, optionally restrict advertised routes, and finally verify the stub status.

Successor is the next-hop router with the lowest metric; Feasible Successor is a backup that meets the feasibility condition; Neighbor is a directly connected EIGRP router.

OSPF requires the forwarding address (FA) in a Type 5 LSA to be reachable via an OSPF internal route (intra-area or inter-area) for the external route to be installed in the routing table. If the FA is not reachable, the router will ignore the LSA and not install the route, even though the LSA exists in the OSPF database and the neighbor adjacency is up.

EIGRP supports a maximum hop count of 255. Unlike RIP, which has a limit of 15 hops, EIGRP can scale to larger networks. The hop count is used as one component in the composite metric, but it is rarely the limiting factor in practice.

Hello packets discover and maintain neighbors; Update packets carry routing information; Query packets ask for alternate paths; Reply packets respond to queries; ACK packets acknowledge reliable delivery.

The output shows 'Prefixes: 3' under the neighbor details, which indicates that the neighbor has advertised exactly three prefixes to R1. This is a direct interpretation of the 'show ip eigrp neighbors detail' command, where the 'Prefixes' field lists the number of routes learned from that neighbor.

Named mode starts with the router eigrp <virtual-name> command, then enters address-family configuration, configures the network, and optionally adjusts timers or other parameters. Finally, the configuration is verified.

EIGRP uses a maximum hop count of 255 to prevent routing loops, though in practice it relies on its DUAL algorithm and feasible successor logic rather than hop count as a primary loop-prevention mechanism. This value is hard-coded in the protocol and cannot be changed, unlike RIP's 15-hop limit.

The command 'passive-interface default' makes all interfaces passive by default, meaning they will not send or receive EIGRP hellos. The subsequent 'no passive-interface GigabitEthernet0/0' overrides this for that specific interface, allowing EIGRP adjacency formation on it.

Hello timer default is 5 seconds on LAN; Hold timer default is 15 seconds; Active timer default is 3 minutes.

EIGRP uses a maximum hop count of 255, which is a hard limit encoded in the protocol's metric field. This allows EIGRP to scale to much larger networks than distance-vector protocols like RIP, which have a hop count limit of 15. The hop count is not used as a primary metric in EIGRP but serves as a loop-prevention mechanism, and routes with a hop count exceeding 255 are considered unreachable.

EIGRP uses a metric based on bandwidth and delay, but it also has a hop count limit. The maximum hop count for EIGRP is 255, though the default is 100.

In the EIGRP metric formula, the K values correspond to specific metric components: K1 is bandwidth, K2 is load, K3 is delay, K4 is reliability. MTU is not a K variable; the EIGRP metric does not include MTU.

To enable unequal-cost load balancing, first ensure feasible successors exist, then set the variance multiplier, optionally adjust the metric offset, and finally verify the load sharing across multiple paths.

EIGRP DUAL first identifies feasible successors via reported distance, then selects the best path as successor. If the successor fails, it checks feasible successors; if none exist, it goes active and queries neighbors. After replies, it computes a new successor.

EIGRP route summarization first requires enabling EIGRP, configuring the network statement, then entering interface configuration mode, applying the summary-address command, and finally verifying the summary route in the routing table.

Passive state indicates a stable route; Active state indicates the router is querying neighbors; Local Computation occurs when a feasible successor exists; Diffusing Computation occurs when no feasible successor exists; Query Origin is the router that starts the query process.

EIGRP neighbor formation begins with sending Hello packets, then exchanging full routing tables via Update packets, acknowledging with ACK packets, and finally entering the Established state where incremental updates are sent.

A feasible successor is a backup route that meets the feasibility condition (reported distance < feasible distance). It is stored in the topology table, not the routing table, and is used immediately if the successor fails.

EIGRP supports manual summarization on any interface and automatic summarization at classful boundaries (disabled by default in modern IOS). Summary routes are advertised with a metric based on the component routes.

Passive is the stable state; Active is when DUAL is actively searching for a new route; Stuck in Active occurs when a query is not answered within the active timer.

Hello packets discover and maintain neighbors; Update packets carry routing information; Query packets ask for successor information; Reply packets respond to queries; ACK packets acknowledge reliable packets.

EIGRP stub routing limits the routes a stub router advertises, preventing it from being used as a transit router. Common stub types include connected, static, summary, and receive-only.

The 'passive-interface default' command sets all interfaces as passive, meaning they do not send or receive EIGRP hellos. The 'no passive-interface' command overrides this for specific interfaces.

EIGRP uses Feasible Distance (FD) as the best metric to a destination, Reported Distance (RD) as a neighbor's metric, and the Feasible Condition (RD < FD) to ensure loop-free paths. Successor is the next-hop router with the lowest FD.