Scott Terminiello wrote: > > It was my understanding that EIGRP only notifies its neighbors > of topology > changes the same way OSPF works. This is in contrast to RIP > which sends out > an update at specified intervals (30 secs for RIPv1) regardless > of whether a > topology change or not.
That doesn't make EIGRP a link-state protocol though. Cats and dogs have a lot of the same features. A cat is not a dog, though. Cats purr. Dogs slobber. End of story. (Cats are superior.) Seriously, a link-state routing protocol creates a mathematical graph that depicts the internetwork. Then it runs a shortest path algorithm to determine the shortest path to all points in the graph when the nodes and links in the graph are known Look up shortest path algorithm in Google. There's some great stuff out there, including animated demonstrations. A shortest path algorithm is used for many applications, especially training computer scientists. It turns out that one can find the shortest path from a given source to all points in a graph in the same time that one can find the shortest path to a single destination, hence this problem is sometimes called the single-source shortest path problem. Dijstra's algorithm, used in most link-state routing protocols, solve the single-source shortest path problem. A distance-vector routing protocol, such as EIGRP, doesn't use a shortest-path algorithm but instead creates a consolidated list of all reachable destinations. (Notice that the data structure is a list, not a graph.) If the list contains multiple entries for a destination (because there are multiple ways to reach the destination), the entries are sorted by metric and the one with the lowest metric is selected. EIGRP does a few other things that most DV protocols don't do. It keeps track of feasible successors, for example. So, it needs more than just a list data structure, but it doesn't have a graph of the internetwork, and it doesn't run the shortest path algorithm. And see Peter's message for the definitive answer! (Well, not the one about ARP switching. :-) Priscilla > > Scott > > ----- Original Message ----- > From: "John Neiberger" > To: > Sent: Friday, March 07, 2003 2:02 PM > Subject: Re: EIGRP for CCIE Written [7:64707] > > > > This really isn't the case. EIGRP is purely distance > vector. In no way > > does it behave like a link state protocol. It establishes > neighbor > > relationships and it uses hellos, as do OSPF and IS-IS, but > those have > > nothing whatsoever to do with whether protocol is DV or LS. > Some people > > get hung up on the complex metric, but who says DV protocols > have to use > > only hop count? > > > > The actual operation of EIGRP is DV. There are no LS > components to > > EIGRP. > > > > Regards, > > John > > > > >>> "Scott Terminiello" 3/7/03 8:28:00 > > AM >>> > > EIGRP is a hybrid. It can be said that it is a distance > vector > > routing > > protocol that acts like a link state routing protocol. > > > > Scott > > ----- Original Message ----- > > From: "Johan Bornman" > > To: > > Sent: Friday, March 07, 2003 7:11 AM > > Subject: EIGRP for CCIE Written [7:64707] > > > > > > > Is EIGRP a Hybrid or Distance Vector protocol? > > Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=64795&t=64707 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
