From: Gregory Gombas (ggombas@gmail.com)
Date: Tue Aug 07 2007 - 06:44:50 ART
How can you alter the REFBW?
On 8/6/07, Szarmach, Douglas <Douglas.Szarmach@cmegroup.com> wrote:
> The 10,000,000 is not a fixed number - that's the REFBW setting and
> might be altered so safer to say REFBW/BW.
>
> Also, the interface delay is expressed in '10's of microseconds' in
> various parts of IOS (stored in units of 10 in the config):
>
> Router(config-if)#delay ?
> <1-16777215> Throughput delay (tens of microseconds)
>
> And in regular microseconds in others (including most show commands):
>
> * x.x.x.x, from y.y.y.y, 1w2d ago, via TenGigabitEthernet1/3
> Route metric is 29440, traffic share count is 1
> Total delay is 150 microseconds, minimum bandwidth is 100000 Kbit
> Reliability 253/255, minimum MTU 1500 bytes
> Loading 8/255, Hops 5
>
> --- and the EIGRP formula calls for total delay in just microseconds so
> the 'delay' needs to be adjusted accordingly, many times involving the
> multiplication of the configured interface delay by 10. I don't
> understand where the 'dividing delay by 10' came from though...perhaps
> working in reverse and returning to the values from running-config?
>
> Douglas Szarmach
> Senior Network Engineer
> +1 312 648 3797
>
> CME Group
> A CME/Chicago Board of Trade Company
> 20 South Wacker Drive
> Chicago, Illinois 60606
> cmegroup.com
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Gregory Gombas
> Sent: Monday, August 06, 2007 10:10 AM
> To: Group study
> Subject: EIGRP metric calculation demystified
>
> Cisco documentation shows the EIGRP metric calculation as this:
> metric = [K1*bandwidth + (K2*bandwidth)/(256 - load) + K3*delay] *
> [K5/(reliability + K4)]
>
> Popular literature says it breaks down to this:
> 256(BW + Delay)
>
> In reality the calculation is this:
> 256((10,000,000/BW)) + (Delay/10))
>
> Does anyone know if this final formula can be found on the DOC cd?
>
> The closes match I could find was on WARP:
> http://www.cisco.com/warp/public/103/3.html
>
> But can this handy formula be accessed from the lab? Its kind of a
> pain to memorize.
>
> Regards,
> Greg
>
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