At 10:51 AM -0400 5/14/02, Chuck wrote: >interesting discussion. > >a couple of thoughts of minor value. > >1) one way to determine whether or not (E)IGRP is a distance vector or not >is to consider that (E)IGRP has a definite diameter limit that is >changeable. Several months ago there was a discussion on this board about >just that. If you have an (E)IGRP network with a diameter of, say, 25, and >you use the appropriate option to change the max distance to 23, some of >your routers and routes will disappear. Even though the routing table shows >(E)IGRP routes with some incomprehensible number in the metric column, the >fact is that the protocols are limited by hops
That's not an essential part of DV, merely a practical sanity check. It is, of course, essential in RIP because RIP uses hop count as an interface cost in building its metric. > >2) as an aside, I suppose it could be argued that all protocols are limited >by the IP TTL, but distance vector protocols all have built in limits to >their diameters. the link state protocols appear to have no such limits, >other than the structural one imposed by IP itself. > >3) I think I am understanding that the "link" in link state refers to >something other than what I originally thought. Does "link" refer to the >neighbor state, the physical wire being up, both, neither? It's a somewhat unfortunate term, in that it doesn't precisely correspond to a concept in actual networking, but in graph theory. The Dijkstra algorithm builds a tree from an arbitrary root, and then grows "links" from there. In reality, router nodes generally form vertices and subnets form arcs, but that's not completely clear-cut, and it's just as easy, from a theoretical standpoint, to assume Dijkstra uses its own arbitrary vertices and treats all types of "links" as potential arcs (i.e., if they are on the best path). > >once again, another great thread, clarifying a lot of things that I "already >knew" > >Oh, one last thing - yes indeed, do not trust anything Cisco says on their >web site. The configuration information is fine. the theoretical stuff is >very often of questionable value. wish I could still find that link about >the reasons for the diameter limitation of EIGRP. It was hilarious. > >Chuck Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=44242&t=43994 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
