Thanks for the feedback...
Very puzzling, but its very close to the answer I got, when I was
trying to find out the reliability K value and also K1 and K3 being
always 1 by default, representing BW & Delay respectively, and also
the fact that MTU is not used for metric calculation.
Thanks Dale and But... mathematics is not my strong point... My query
is fully answered...
Kind Regards,
Jowi.
From: But Nicky [mailto:[email protected]]
Sent: 11 August 2009 03:18 PM
To: Dale Shaw
Cc: Jowi Nkwe (JM); [email protected]
Subject: Re: [OSL | CCIE_RS] EIGRP K Values Represenation
Hi,
K1 relates to BW.
K2 relates to BW, Load.
K3 relates to Delay.
K4, K5 relates to Reliability.
MTU is just used for "tie-break"
HTH,
But Nguyen.
On Tue, Aug 11, 2009 at 3:55 PM, Dale Shaw <[email protected]
<mailto:dale.shaw%[email protected]> > wrote:
Hi,
On Tue, Aug 11, 2009 at 6:47 PM, Jowi Nkwe (JM)<[email protected]>
wrote:
>
> Please clarify this, what is the correct EIGRP K values
> representation. That is K1, K2, K3, K4, K5, I know they represent
> bandwith, dealy, load, mtu, reliability... But please confirm the
> following
> K1 = ......
> K2 = ......
> K3 = ......
> K4 = ......
> K5 = ......
>
> I've searched the doccd, but this is not explicitly indicated as
such.
> Metric weight command under EIGRP process does not offer much help.
>From the DocCD (command reference for 'metric weights (EIGRP)'):
"If k5 equals 0, the composite EIGRP metric is computed according to
the following formula:
metric = [k1 * bandwidth + (k2 * bandwidth)/(256 - load) + k3 * delay]
"If k5 does not equal zero, an additional operation is performed:
metric = metric * [k5/(reliability + k4)]
So the weights don't strictly map one-to-one with the 5 elements
mentioned -- bandwidth, delay, load, reliability and MTU.
In fact, MTU values, while tracked along a path, are not actually used
in the composite metric calculation at all -- k5 might seem to map to
MTU because that's what the context-sensitive CLI help indicates, but
you can see that the actual MTU value is not used in the above
calculation.
Using the default weights, the formula is effectively simplified to:
256 * (10,000,000 / BANDWIDTH_IN_KBPS(min)) + 256 *
(DELAY_IN_uSEC(sum) / 10)
e.g. if the minimum end-to-end bandwidth is 100Kbps and the total
end-to-end delay (in microseconds) is 124000, the composite metric is:
256 * (10,000,000 / 100) = 25600000 +
256 * (124000 / 10) = 3174400 =
28774400
The first 'metric weights' parameter -- ToS --
is always zero. An original design goal was for EIGRP to be able to do
Type of Service routing, but this was never implemented.
cheers,
Dale
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