Some networks I have worked with took the average latency of each link and assigned that (with some constant multiple) as the interface cost. Of course this all fails miserably if you are using anything like MPLS underneath your OSPF. Owen On Jan 24, 2014, at 12:26 PM, Erik Sundberg <ESundberg@nitelusa.com> wrote:
I understand OSPF default calculation for cost doesn't include delay. I am looking for a formula that I can use to manually set the OSPF costs that factors in delay.
When using OSPF's default costs, the shortest path is not always the optimal path.
Example
New York to Los Angeles. Assuming all links are the same bandwidth and have a ospf cost of 1.
Path 1 (75ms) - OSPF Cost 2 - New York > Dallas > Los Angeles
Path 2 (65ms) - OSPF Cost 3 - New York > Chicago > Denver > Los Angeles
If I left the default cost's alone then path 1 would win because it has a lower ospf cost, however it take traffic 10ms longer to get there.
However I would like traffic to take Path 2 by adjusting the OSPF cost.
I am looking for a formula that other people are using .p
Thanks
Erik
-----Original Message----- From: Randy [mailto:randy_94108@yahoo.com] Sent: Thursday, January 23, 2014 9:03 PM To: Erik Sundberg; nanog@nanog.org Subject: Re: OSPF Costs Formula that include delay.
----- Original Message -----
From: Erik Sundberg <ESundberg@nitelusa.com> To: "nanog@nanog.org" <nanog@nanog.org> Cc: Sent: Thursday, January 23, 2014 4:47 PM Subject: OSPF Costs Formula that include delay.
What is everyone using for an OSPF cost formula that factors in a circuits delay and bandwidth (10M-100G)???
Thanks in advance
umm..are you sure your question is not about EIGRP? OSPF has no concept of interface-delays.
The default reference bandwidth for OSPF is 100M
In your case if you set your reference bandwidth to 100000 your 100G links would have a link cost of 1, 10G - 10, 1G-100, 100M-1000 and 10M-10000
A vendor specific list would be a better place to ask.
./Randy
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