CCIE Pursuit Blog

May 30, 2009

Core Knowledge Question of the Day: 30 May 2009

Which protocol enables EIGRP routers to determine whether a path advertised by a neighbor is looped or loop-free, and allows a router running EIGRP to find alternate paths without waiting on updates from other routers?

Highlight for answer: Diffusing update algorithm (DUAL)

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3 Comments »

  1. this question was a bit perplexing since you said “which protocol…”
    😉

    Keep up the good work on the questions.

    Comment by luisgarcia — May 30, 2009 @ 9:36 am | Reply

  2. @luisgarcia – I would have been thrown off by the wording too. 🙂 I would not have thought of DUAL as a “protocol”. That’s why I chose it. I pulled this from Cisco’s documentation:

    “Additionally, EIGRP contains several important protocols that greatly increase its operational efficiency relative to other routing protocols. One of these protocols is the Diffusing update algorithm (DUAL) developed at SRI International by Dr. J.J. Garcia-Luna-Aceves. DUAL enables EIGRP routers to determine whether a path advertised by a neighbor is looped or loop-free, and allows a router running EIGRP to find alternate paths without waiting on updates from other routers.”

    http://www.cisco.com/en/US/docs/internetworking/technology/handbook/Enhanced_IGRP.html#wp1020549

    Comment by cciepursuit — May 30, 2009 @ 9:43 am | Reply

  3. Good one,

    I for some reason went for RTP, reliable transport protocol ..only beacuse your question was asking for “which protocol”. DUAL, its is ..etched on my mind now.

    Comment by Andy Hogard — May 30, 2009 @ 12:00 pm | Reply


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