From: Luca Hall (lhall@setnine.com)
Date: Thu Dec 11 2008 - 20:06:24 ARST
by default the reference bw is 100M, the calc is
reference bw / interface bw so for a fa interface you have 100M / 100M = 1
if you change the auto-cost reference-bandwidth to 1000
then a 1000M interface will have a cost of 1 (1000M/1000M).
since you want a cost of 5 just multiply the reference-bandwidth by
5 giving you 5000 for the answer.
----- Original Message -----
From: nouman abbasi <abbasi.nouman@gmail.com>
To: Cisco certification <ccielab@groupstudy.com>
Sent: Thu, 11 Dec 2008 16:54:55 -0500 (EST)
Subject: OSPF COST
*(Q) Modify OSPF Cost to set value of COST of 1000M link 5*
Hi GS,
I am unable to understand the question ; can someone help
to understand with a correct solution.
I have got the following note from wordpress.com
"
CISCO provides a solution within certain router IOS software to be able to
control how OSPF calculates the default metrics for an interface. This
feature is enabled under the *router ospf* process using the *ospf auto-cost
reference-bandwidth ref-bw*. Where ref-bw is the rate in megabits per second
(bandwidth). The range is 1 to 4294967; the default is 100. The formula is
now changed to be Reference-bandwidth/interface bandwidth. This feature
allows us to globally change how the costs are determined by interface
speed. This command was introduced in CISCO IOS release 11.2.
Conclusion:- If you are using OC-3 and higher links, you should enable ospf
auto-cost reference-bandwidth under your router ospf process. Depending on
your organizations routing policies you can implement different methods. The
best practice here is specifying ip ospf cost manually for every interface.
This is a best method to avoid confusion in route selection.
"
Blogs and organic groups at http://www.ccie.net
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