BSCI Question (EIGRP Metric Formula)

Jan 6th, 2009

Hi,

I am working on the BSCI test and came across the EIGRP formula for calculating metric of routes. The problem is that how I see it the derivative of the formula will always be 0. Here is the formula ...

metric=256x(K1xBW + K2xBW/256-load + K3xdelay) x K5/reliability+K4

K1 and K3 are 0 by default.

K2, K4, and K5 are 0 by default.

So ... that means the end of that formula will always be multiplied by 0 since K5 is 0 (0/0+reliability).

What am I missing here?

Richard

Richard

According to the command reference the version of the calculation that you have is specifically for situations where K5 is non-zero. Here is what the command reference says:

If k5 equals 0, the composite IGRP or 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)]

Here is the link is you want to see more detail:

http://www.cisco.com/en/US/docs/ios/12_2/iproute/command/reference/1rfeigrp.html#wp1023638

HTH

Rick

Overall Rating: 5 (1 ratings)

Replies

Richard Burts Tue, 01/06/2009 - 07:54

Richard

According to the command reference the version of the calculation that you have is specifically for situations where K5 is non-zero. Here is what the command reference says:

If k5 equals 0, the composite IGRP or 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)]

Here is the link is you want to see more detail:

http://www.cisco.com/en/US/docs/ios/12_2/iproute/command/reference/1rfeigrp.html#wp1023638

HTH

Rick

richard.m.gilbert Tue, 01/06/2009 - 08:04

Rick,

Thanks. It was really bugging me because the book doesn't say that. Thanks!

Richard