At 01:01 PM 7/2/01, John Neiberger wrote:
>EIGRP has some of the benefits of LS protocols, such as a hello
>subprotocol and triggered updates, but its behavior is entirely distance
>vector. It still uses split horizon with poison reverse; it does not
>have a complete view of the area topology; it does not pass link-state
>information between participating routers, it is simply passing along
>Distance (metric) and Vector (direction) information.
>
>[BTW: I'm not sure if that's the proper use of the term 'vector', but
>I brought that with me from physics classes.]
Absolutely a good use of the word vector. I love it when people think about
what it really means! ;-)
Here's how I describe distance vector:
The term vector means direction or course. A distance vector is a course
that also includes information on the length of the course. Many
distance-vector routing protocols specify the length of the course with a
hop count. A hop count specifies the number of routers that must be
traversed to reach a destination network. (For some protocols, hop count
means the number of links, rather than the number of routers.) Some
distance-vector protocols, such as IGRP and EIGRP, have a more advanced
measure of distance, based on bandwidth, delay, reliability, and other
factors. A distance-vector routing protocol maintains and transmits a
routing table that lists known networks and the distance to each network.
Link-state routing protocols do not exchange routing tables. Instead,
routers running a link-state routing protocol exchange information about
the status of their directly connected links. Each router learns enough
information from peer routers to build its own routing table. A link-state
router sends a multicast packet advertising its link states on a periodic
basic. Other routers forward the multicast packet to peer routers in the
internetwork.
Enhanced IGRP is compatible with IGRP and provides an automatic
redistribution mechanism to allow IGRP routes to be imported into Enhanced
IGRP, and vice versa. Enhanced IGRP can also redistribute routes for RIP,
IS-IS, BGP, and OSPF. In addition, Enhanced IGRP offers support for
AppleTalk and Novell routing, and can redistribute RTMP and IPX RIP routes,
and IPX Service Advertising Protocol (SAP) updates.
One of the main goals of Enhanced IGRP is to offer very quick convergence
on large networks. To meet this goal, the designers of Enhanced IGRP
adopted the diffusing-update algorithm (DUAL) that Dr. J.J.
Garcia-Luna-Aceves developed at SRI International. DUAL specifies a method
for routers to store neighbors' routing information so that the routers can
switch to alternate routes very quickly. Routers can also query other
routers to learn alternate routes and send hello packets to determine the
reachability of neighbors.
By the way, I think DUAL also guarantees a loop-free topology, so there is
no need for a hold-down mechanism, which is another feature that minimizes
convergence time and makes EIGRP more "advanced" than other DV protocols.
Howard and Pamela can correct me if I have over-simplified too much! But I
think it's a good description for starters. ;-)
Priscilla
>It's advanced, certainly, but it is definitely not a link state
>protocol.
>
>Cisco likes to call it a hybrid for marketing purposes but it's really
>nothing more than a souped-up DV protocol.
>
>Regards,
>John
>
> >>> "Charles Manafa" 7/2/01 10:17:38 AM
> >>>
>EIGRP is an advanced Distance Vector protocol, but also known as a
>hybrid
>protocol, because it exhibits attributes from both world.
>
>CM
>
>-----Original Message-----
>From: CCIE TB
>To: [EMAIL PROTECTED]
>Sent: 02/07/01 17:02
>Subject: Is EIGRP a DV or LS protocol [7:10657]
>
>Hi Group members,
>
>Is EIGRP a Distance Vector or a Link State protocol. I thought it is a
>Link
>State until I read Cisco BSCN book, which classify it as both. Is that
>
>possible.
>
>Regards to all
>
>Adiah
>________________________________________________________________________
>_
>Get Your Private, Free E-mail from MSN Hotmail at
>http://www.hotmail.com.
________________________
Priscilla Oppenheimer
http://www.priscilla.com
Message Posted at:
http://www.groupstudy.com/form/read.php?f=7&i=10686&t=10657
--------------------------------------------------
FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html
Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
