I am under the impression that if a router had more than one route with the same prefix length in its database(s) then it would choose the one with the lowest AD to place in its routing table. As in John's example only when the prefixes are different are they both in the routing table. AFAIK, a Cisco router will load balance between paths but only when it involves the same protocol, it will not load balance between differing ADs. Please educate me if I am incorrect.
Jeff >From: "Chuck" >Reply-To: "Chuck" >To: [EMAIL PROTECTED] >Subject: Re: longest match vs. other metrics [7:41692] >Date: Tue, 16 Apr 2002 23:05:34 -0400 > >perhaps I am misunderstanding your answer. > >a router always forwards based on the longest match. this is a requirement, >per RFC 1812. > >if there are two or more routes in a routing table of the same prefix >length, then, in accordance with the rules regarding load sharing, more >than >one route / interface can be used. > >admin distance is the tiebreaker a ( Cisco ) router uses when determining >which routes of identical prefix length, but learned from different routing >protocols, to place into the routing table in the first place. > >John N's post on this topic is an excellent explanation of the two >different >processes. > >Chuck > > >""Jeff Smith"" wrote in message >[EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > Sean, the longest match is the first characteristic considered. So, >using > > your example, IOS will choose the route that has the longest prefix >match- > > only when they are the same will the decison come down to administratice > > distance between protocols. > > > > P.S. > > Due to your connections can I get some Red Sox tickets? > > > > > > >From: "Sean Wolfe" > > >Reply-To: "Sean Wolfe" > > >To: [EMAIL PROTECTED] > > >Subject: longest match vs. other metrics [7:41692] > > >Date: Tue, 16 Apr 2002 22:08:54 -0400 > > > > > >Quick question, hope it's not too trivial: > > > > > >When a router decides to forward a packet based on the longest match > > >principle, does this supersede other factors? > > > > > >For example, if there is a route to network A via EIGRP, but a more > > >specific > > >route available via OSPF, does it choose OSPF because of longest match, >or > > >EIGRP because of lower administrative distance (90 vs. 110)? > > > > > >Thanks folks, fun reading your posts as always. Wish me luck as I take >BCSN > > >this week. -Sean. > > _________________________________________________________________ > > Chat with friends online, try MSN Messenger: http://messenger.msn.com _________________________________________________________________ Chat with friends online, try MSN Messenger: http://messenger.msn.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=41712&t=41692 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
