From: mani poopal (mani_ccie@yahoo.com)
Date: Tue Sep 20 2005 - 20:10:10 GMT-3
Guys,
Simple rule in Cisco, if a route is learned by more than one routing protocols or same routing protocols, selection in the routing table is based on:
1. Longest prefix
2. Lowest AD(administrative distance)
3. If same AD(same routing protocols), Lowest Metric(for rip hop count, ospf cost etc)
4. If Metric also same, then all routing protocols support equal cost path load balancing
5. When metrics are different and if you want to do load balancing, it is called unequal cost path load balancing, only cisco's protocol(igrp and eigrp) support this feature by variance command.
hope this helps for beginers
Mani
sundar.palaniappan@verizon.com wrote:
Comparing metric of two different protocols would be like comparing apples
and oranges.
I believe, the protocol that owns the native administrative distance wins.
Let's say, a router learns NET X via RIP & OSPF and you lower the distance
to 110 for the RIP route, router will install the OSPF route in the routing
table and not the RIP route.
I don't have any documented explanation for the behavior. But, it makes
sense the IOS prefers the native admin distance over the modified one when
both are same.
HTH,
Sundar Palaniappan
CCIE #14532
"Dan Espino"
om> cc:
Sent by: Subject: Re: Administrative distance tie
nobody@groupstudy
.com
09/20/2005 05:10
PM
Please respond to
"Dan Espino"
OK, rip had a hop count to 3 and ospf has a cost of 10.
Now who wins
On 9/20/05, rosy bird wrote:
>
> i guess...here is where metric comes into picture...
>
> On 9/21/05, Dan Espino wrote:
> >
> > If 2 protocols have the same AD (because one was adjusted), and the
same
> > prefix length, how does the router determine which to choose?
> >
> > _______________________________________________________________________
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