From: Szarmach, Douglas (Douglas.Szarmach@cmegroup.com)
Date: Mon Aug 06 2007 - 16:32:17 ART
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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