How Are EIGRP and OSPF Similar in Routing Protocol Behavior?

350-401 By islever Editorial Last updated Aug 24, 2026

Short answer

B Both protocols use hello packets to discover neighbors.

Question

In which way are EIGRP and OSPF similar?

Both protocols support autosummarization.
Both protocols use hello packets to discover neighbors. Correct Answer
Both protocols support unequal-cost load balancing.
Both protocols send updates using unicast addresses.

Key Takeaways

The question tests knowledge of shared operational behaviors between EIGRP and OSPF, with the common trap being confusion over autosummarization or update delivery methods.

EIGRP and OSPF are both Interior Gateway Protocols (IGPs) that use Hello packets to discover and maintain neighbor adjacencies. Community consensus confirms that while they differ in algorithm and update mechanisms, their use of Hello packets for neighbor discovery is a key similarity.

Common mistake: Option A is frequently chosen because candidates mistakenly believe OSPF supports autosummarization like EIGRP; however, OSPF does not support autosummarization, making B the correct answer.

Expert Analysis

Why the Answer Is Correct

Both EIGRP and OSPF use Hello packets to discover neighbors and maintain adjacency relationships. This is a fundamental similarity between the two protocols, regardless of their differing internal algorithms (DUAL vs. SPF). Hello packets are sent periodically to ensure neighbor liveness, and this behavior is consistent across both protocols.

Why the Other Options Are Wrong

Option A is incorrect because OSPF does not support autosummarization, while EIGRP does (though it is disabled by default in newer IOS versions). Option C is incorrect because OSPF only supports equal-cost load balancing, whereas EIGRP supports both equal and unequal-cost load balancing. Option D is incorrect because both protocols use multicast addresses for updates—OSPF uses 224.0.0.5 and 224.0.0.6, while EIGRP uses 224.0.0.10.

Community Comment Notes

Comment [3] provides an excellent summary of similarities and differences, noting that both protocols are IGPs, support VLSM and ECMP, and use Hello packets. Comment [2] correctly clarifies that OSPF uses multicast for LSAs, while EIGRP uses multicast (224.0.0.10) and can also use unicast in specific scenarios. Comment [1] reinforces that OSPF does not support autosummarization, making A incorrect.

Exam Strategy

When comparing routing protocols, focus on their operational behaviors (e.g., neighbor discovery, update mechanisms) rather than just their algorithms. Eliminate options that describe features unique to one protocol, such as autosummarization or unequal-cost load balancing.

Community Votes

100%

100% of anonymous learners picked answer B. Votes are pick records left by other test-takers — they are not the verified answer.

Discussion 5 contributions

Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.

From public community threads 5

slacker_at_work 👍 2 Answered B

A is incorrect because OSPF does not support autosummarization by default, while EIGRP does. B okidoki & correcto C wrong as EIGRP does support unequal-cost LB D nope, this is done by Multicast
AbdullahMohammad251 👍 1 Answered B

A. Incorrect, Auto-summary in OSPF is only permitted on ASBR and ABR routers. On the other hand, EIGRP auto-summary could be configured on any router. C. Incorrect, OSPF doesn't support unequal-cost load balance. EIGRP supports equal and non-equal load balancing. D. Incorrect, OSPF uses multicast addresses (224.0.0.5 and 224.0.0.6) to send LSAs, while EIGRP can use both multicast (224.0.0.10) and unicast. B. Correct! Both protocols use hello packets to discover their neighbor with different hello,& dead timers by default.
chiacche 👍 1 Answered B

Similarities : EIGRP and OSPF are both Internal Gateway Protocols (IGP), support VLSM and ECMP, and use Hello packets to establish neighbor relationships. Difference : EIGRP is Cisco's proprietary Advanced Distance Vector Protocol that uses the DUAL algorithm, while OSPF is an open standard link state protocol that uses the SPF algorithm.
[Removed] 👍 1

B is correct. but what about D ?
Mizuchan 👍 2 Answered B

Correct

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