Eigrp practice questions

A router has the following routes in its routing table: a static route to 10.60.4.16/28, an OSPF route to 10.60.4.0/24, and an EIGRP route to 10.60.0.0/16. Which route will be used for a packet destined to 10.60.4.17?

Exhibit

R1# show ip route
O    10.60.4.0/24 [110/20] via 192.0.2.2
S    10.60.4.16/28 [1/0] via 192.0.2.6
D    10.60.0.0/16 [90/30720] via 192.0.2.10

Destination being tested: 10.60.4.17

Trap 1: The OSPF route to 10.60.4.0/24

This is wrong because the /24 is less specific than the /28.

Trap 2: The EIGRP route to 10.60.0.0/16

This is wrong because the /16 is broader than both other matches.

Trap 3: No route at all

This is wrong because the destination clearly matches all three shown prefixes.

A
The static route to 10.60.4.16/28
This is correct because the destination falls inside the more specific /28 prefix.
B
The OSPF route to 10.60.4.0/24
Why wrong: This is wrong because the /24 is less specific than the /28.
C
The EIGRP route to 10.60.0.0/16
Why wrong: This is wrong because the /16 is broader than both other matches.
D
No route at all
Why wrong: This is wrong because the destination clearly matches all three shown prefixes.

Question 2mediummulti select

A router learns a route to 172.16.0.0/16 via OSPF (administrative distance 110) and a route to 172.16.10.0/24 via EIGRP (administrative distance 90). No other overlapping routes exist. Which TWO statements about how the router handles these routes are correct?

Trap 1: The router installs only the EIGRP route because it has a lower…

Administrative distance is compared only for routes with the same prefix length. Here the routes have different prefix lengths, so both are installed.

Trap 2: Traffic to 172.16.10.100 is forwarded using the OSPF route.

Longest-prefix matching selects the most specific route. Because 172.16.10.100 falls within the /24 subnet, the EIGRP route is used.

Trap 3: The EIGRP route is used for all traffic destined to any address…

The EIGRP route covers only the 172.16.10.0/24 subnet. Other subnets within the /16 still use the OSPF route.

A
The router installs only the EIGRP route because it has a lower administrative distance.
Why wrong: Administrative distance is compared only for routes with the same prefix length. Here the routes have different prefix lengths, so both are installed.
B
Both the OSPF and EIGRP routes are installed in the routing table.
Since the routes have different prefix lengths, they are treated as separate destinations and both are installed.
C
Traffic to 172.16.10.100 is forwarded using the OSPF route.
Why wrong: Longest-prefix matching selects the most specific route. Because 172.16.10.100 falls within the /24 subnet, the EIGRP route is used.
D
The EIGRP route is used for all traffic destined to any address within 172.16.0.0/16.
Why wrong: The EIGRP route covers only the 172.16.10.0/24 subnet. Other subnets within the /16 still use the OSPF route.
E
The OSPF route is used for destinations within 172.16.0.0/16 that are not part of the 172.16.10.0/24 subnet.
Because the /24 is a more specific route, the OSPF /16 serves as a covering route for any addresses that do not match the longer prefix.

Study the full EIGRP explanation →

Question 3mediummultiple choice

Why is RIP rarely chosen for large modern enterprise networks?

Trap 1: It does not support IPv4

RIP absolutely supports IPv4.

Trap 2: It cannot run on routers and only works on switches

RIP is a routing protocol for routers, not a switch-only feature.

Trap 3: It requires link-state advertisements

RIP is a distance-vector protocol, not a link-state protocol.

A
It does not support IPv4
Why wrong: RIP absolutely supports IPv4.
B
It scales poorly due to slow convergence and hop-count limitations
Correct. Limited scale and slower convergence are major reasons RIP is rarely used in large environments.
C
It cannot run on routers and only works on switches
Why wrong: RIP is a routing protocol for routers, not a switch-only feature.
D
It requires link-state advertisements
Why wrong: RIP is a distance-vector protocol, not a link-state protocol.

Question 4hardmultiple choice

A router learns the same destination from EIGRP and OSPF. The EIGRP route has a metric of 1000, and the OSPF route has a metric of 10. Which route is installed by default?

Trap 1: The OSPF route, because 10 is lower than 1000

This is wrong because metrics from different protocols are not compared directly until administrative distance is considered.

Trap 2: Both routes automatically install for load balancing

This is wrong because routes from different protocols are not automatically load-balanced simply because they reach the same destination.

Trap 3: Neither route installs until the administrator chooses manually

This is wrong because the router can select a preferred route automatically using its normal decision process.

A
The OSPF route, because 10 is lower than 1000
Why wrong: This is wrong because metrics from different protocols are not compared directly until administrative distance is considered.
B
The EIGRP route, because its source has a lower default administrative distance
This is correct because EIGRP is preferred over OSPF by default due to administrative distance.
C
Both routes automatically install for load balancing
Why wrong: This is wrong because routes from different protocols are not automatically load-balanced simply because they reach the same destination.
D
Neither route installs until the administrator chooses manually
Why wrong: This is wrong because the router can select a preferred route automatically using its normal decision process.

Question 5mediummultiple choice

A router learns the same prefix from both OSPF and EIGRP. Which route is installed by default?

Trap 1: The OSPF route because OSPF is link-state

Protocol type alone does not determine preference.

Trap 2: The route with the lower metric value regardless of protocol

Metrics are not directly compared across different protocols.

Trap 3: Both routes are always installed

Both routes are not automatically installed just because the prefix matches.

A
The OSPF route because OSPF is link-state
Why wrong: Protocol type alone does not determine preference.
B
The EIGRP route because it has the lower administrative distance
Correct. Lower AD wins between different routing protocols.
C
The route with the lower metric value regardless of protocol
Why wrong: Metrics are not directly compared across different protocols.
D
Both routes are always installed
Why wrong: Both routes are not automatically installed just because the prefix matches.

Question 6mediummultiple choice

A router learns 10.10.10.0/24 from OSPF and EIGRP at the same time. OSPF reports a metric of 20, and EIGRP reports a metric of 30720. Which route is installed in the routing table by default?

Trap 1: The OSPF route, because 20 is lower than 30720

Metrics are only compared within the same routing protocol, not across different ones.

Trap 2: Both routes, because they point to the same prefix

Equal-cost load balancing does not occur across different protocols just because the destination matches.

Trap 3: Neither route, because the metrics are not comparable

One of the routes is selected; the metrics being different types does not prevent route installation.

A
The OSPF route, because 20 is lower than 30720
Why wrong: Metrics are only compared within the same routing protocol, not across different ones.
B
The EIGRP route, because its administrative distance is lower
Correct. EIGRP wins because its default administrative distance is lower than OSPF.
C
Both routes, because they point to the same prefix
Why wrong: Equal-cost load balancing does not occur across different protocols just because the destination matches.
D
Neither route, because the metrics are not comparable
Why wrong: One of the routes is selected; the metrics being different types does not prevent route installation.

Question 7mediummultiple choice

A router learns 172.16.40.0/24 from OSPF with AD 110 and metric 20. It also learns the same prefix from EIGRP with AD 90 and feasible distance 30720. Which route is installed?

Trap 1: The OSPF route because metric 20 is lower than 30720

OSPF metric is not compared against an EIGRP feasible distance.

Trap 2: Both routes because ECMP is automatic across different protocols

Equal-cost load balancing does not happen just because two protocols know the route.

Trap 3: Neither route until one is redistributed into the other protocol

Redistribution is not required to install a learned route.

A
The OSPF route because metric 20 is lower than 30720
Why wrong: OSPF metric is not compared against an EIGRP feasible distance.
B
The EIGRP route because its administrative distance is lower
Different protocols are compared by AD first.
C
Both routes because ECMP is automatic across different protocols
Why wrong: Equal-cost load balancing does not happen just because two protocols know the route.
D
Neither route until one is redistributed into the other protocol
Why wrong: Redistribution is not required to install a learned route.

Study the full EIGRP explanation →

Question 8hardmultiple choice

A router shows the following routing table entries for the same destination:

O    10.10.50.0/24 [110/20] via 192.168.12.2, GigabitEthernet0/0
D    10.10.50.0/24 [90/30720] via 192.168.13.2, GigabitEthernet0/1

Which route will become the active route in the routing table?

Trap 1: The OSPF route, because its metric is lower

This is the classic wrong answer because the OSPF metric looks smaller. The mistake is treating metric values from different protocols as if they mean the same thing. They do not. The router first compares administrative distance when choosing between route sources such as OSPF and EIGRP, and only then uses metrics within a single protocol's own logic.

Trap 2: Both routes, because the prefixes are identical

Routers do not automatically install both routes just because the prefix is identical. When the entries come from different routing protocols, the router chooses the source with the best administrative distance first. Only after that, and usually within the same protocol, do equal-cost load-balancing rules come into play.

Trap 3: Neither route, because the metrics use different scales

It is true that the metrics use different scales, but that does not mean the router rejects both routes. Cisco routers solve that comparison problem by using administrative distance first. In this case they still choose one route, and it is the EIGRP route.

A
The OSPF route, because its metric is lower
Why wrong: This is the classic wrong answer because the OSPF metric looks smaller. The mistake is treating metric values from different protocols as if they mean the same thing. They do not. The router first compares administrative distance when choosing between route sources such as OSPF and EIGRP, and only then uses metrics within a single protocol's own logic.
B
The EIGRP route, because its administrative distance is lower
Correct. This is correct. EIGRP wins here because its default administrative distance of 90 is lower than OSPF's 110, so the router trusts the EIGRP route more when both advertise the same destination prefix.
C
Both routes, because the prefixes are identical
Why wrong: Routers do not automatically install both routes just because the prefix is identical. When the entries come from different routing protocols, the router chooses the source with the best administrative distance first. Only after that, and usually within the same protocol, do equal-cost load-balancing rules come into play.
D
Neither route, because the metrics use different scales
Why wrong: It is true that the metrics use different scales, but that does not mean the router rejects both routes. Cisco routers solve that comparison problem by using administrative distance first. In this case they still choose one route, and it is the EIGRP route.