EIGRP replies

Answered Question
May 21st, 2008

Hi,

The following question is in the Cisco Press Self study guide:

1. Which of the following describes how a reply to an EIGRP query is sent?

a. Multicast

b. Best effort unicast

c. A reliable unicast

d. A reliable multicast

The books saids the correct answer is B. But I think it should be C, am I wrong??

FOr what I've read and study about EIGRP, it uses Multicast and RTP, I have never read something about best effort unicasts.

I have this problem too.
0 votes
Correct Answer by sundar.palaniappan about 8 years 6 months ago

I agree, the answer should be C. As you can see from the explanation below, EIGRP query replies are reliable unicast packets to the originator. The book answer might be a typo error.

From CCO:

Query and reply packets are sent when a destination has no feasible successors. Query packets are always multicast. Reply packets are sent in response to query packets to instruct the originator not to recompute the route because feasible successors exist. Reply packets are unicast to the originator of the query. Both query and reply packets are transmitted reliably.

http://www.cisco.com/en/US/docs/internetworking/technology/handbook/Enhanced_IGRP.html

HTH

Sundar

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Correct Answer
sundar.palaniappan Wed, 05/21/2008 - 14:17

I agree, the answer should be C. As you can see from the explanation below, EIGRP query replies are reliable unicast packets to the originator. The book answer might be a typo error.

From CCO:

Query and reply packets are sent when a destination has no feasible successors. Query packets are always multicast. Reply packets are sent in response to query packets to instruct the originator not to recompute the route because feasible successors exist. Reply packets are unicast to the originator of the query. Both query and reply packets are transmitted reliably.

http://www.cisco.com/en/US/docs/internetworking/technology/handbook/Enhanced_IGRP.html

HTH

Sundar

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