From: Brian McGahan (brian@cyscoexpert.com)
Date: Wed May 28 2003 - 18:36:40 GMT-3
Brent,
What do you mean by "Load and reliability should not be included
in the calculation (by changing k values) because EIGRP does not send
out updates if they change." ?
Brian McGahan, CCIE #8593
Director of Design and Implementation
brian@cyscoexpert.com
CyscoExpert Corporation
Internetwork Consulting & Training
Toll Free: 866.CyscoXP
Fax: 847.674.2625
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
Of
> Brent D. Stewart
> Sent: Wednesday, May 28, 2003 3:37 PM
> To: Danny.Andaluz@triaton-na.com; ccielab@groupstudy.com
> Subject: RE: EIGRP metric (just to be sure)
>
> No. For an excellent discussion of this, refer to Alvaro Retana's
book
> "EIGRP for IP".
>
> EIGRP builds a metric using the equation:
>
> Metric= (k1*bw + k2*bw/(256-load) + k3*delay) (k5/(reliability+k4)
>
> By default, k1=1, k2=0, k3=1, k4=0, k5=0 and k2, k4, and k5 really
> shouldn't ever be changed. K1 and k3 are very seldom changed. If
k5=0,
> the last part is ignored, so this reduces to:
>
> Metric= bw + delay
>
> Each of these deserves a discussion.
>
> "bw" is actually 10^7/min(bw). In other words, the bw part uses the
> slowest link along the path and is inversely proportional to 1
million.
>
> "delay" is an accumulation of all interface delays along the path.
>
> Load and reliability should not be included in the calculation (by
> changing k values) because EIGRP does not send out updates if they
> change. MTU isn't even an option, but the idea was that it might be
> used for minimum MTU discovery along a path. As far as I know, this
was
> never implemented.
>
> EIGRP actually also tracks hops. The default max is 100. EIGRP
doesn't
> use this in the metric, it's there as a loop-detection mechanism.
>
> Regards,
>
> Brent D. Stewart
>
> -----Original Message-----
> From: Danny.Andaluz@triaton-na.com
[mailto:Danny.Andaluz@triaton-na.com]
>
> Sent: Wednesday, May 28, 2003 2:41 PM
> To: ccielab@groupstudy.com
> Subject: EIGRP metric (just to be sure)
>
> Hello, Group. Is the below correct with regards to how eigrp picks a
> best
> route? Does it do it like the below or does each value get taken into
> account for the composite metric?
>
> BW
> Delay (in case of tie with BW) ?
> relia (in case of tie with delay) ?
> load (in case of tie with relia) ?
> MTU (in case of tie with load) ?
>
> Thanks,
> Danny
>
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