From: Howard C. Berkowitz (hcb@xxxxxxxxxxxx)
Date: Wed Mar 13 2002 - 14:34:06 GMT-3
At 5:10 PM +0200 3/13/02, Shadi wrote:
>Hi,
>
>During my studies, I saw that we should always nail the DR Router by ip ospf
>priority, so that always that router be the DR when using Frame-relay with
>broadcast or non broadcast network type.
>
>What about Ethernet network why we don't nail it too?
>
>Shadi
The basic reason is that regular Ethernet is a full broadcast medium,
so, from a topological viewpoint, any node can be the DR and every
other node can reach it. With hub-and-spoke topologies like frame,
only the hub (and backup hubs) are reachable by the spokes, so the
hub MUST be DR.
There are rare cases where you might, for performance reasons, nail
preference on an Ethernet. I had a case where we had a number of
2500's with fairly heavily loaded CPU (doing IBM stuff) sharing an
Ethernet with a pair of 7200s. We made a point to make the 7200's DR
eligible and the 2500's not, to be sure we didn't put too much
processing load on the 2500's.
In general, though, if processing load is enough of a concern that DR
roles will affect it, you need a router with a more powerful
processor.
-- "What Problem are you trying to solve?" ***send Cisco questions to the list, so all can benefit -- not directly to me*** ******************************************************************************* * Howard C. Berkowitz hcb@gettcomm.com Chief Technology Officer, GettLab/Gett Communications http://www.gettlabs.com Technical Director, CertificationZone.com http://www.certificationzone.com "retired" Certified Cisco Systems Instructor (CID) #93005
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