From: johnsheahan@charter.net
Date: Thu Apr 28 2005 - 21:15:15 GMT-3
Thank you for expaining that. I have asked many a person and many either
don't know or say that every time they tried to calculate it manually, it's
always wrong.
----- Original Message -----
From: "Paresh Khatri" <Paresh.Khatri@aapt.com.au>
To: <johnsheahan@charter.net>; "Sheahan, John" <John.Sheahan@priceline.com>;
<ccielab@groupstudy.com>
Sent: Thursday, April 28, 2005 8:11 PM
Subject: RE: EIGRP Composite Metric Calculation
Hi John,
If the BW is 10,000kbps and the cumulative delay is 7000 microseconds, you
get the following:
Metric = 256*(10^7/10^4) + 256*7000/10
= 256*1000 + 256 * 700
= 256000 + 179200
= 435200
which matches with what you are seeing...
Note that the delay value you use is in tens of microseconds, so you have to
divide the value by 10 before using it in the formula.
HTH,
Paresh.
-----Original Message-----
From: johnsheahan@charter.net [mailto:johnsheahan@charter.net]
Sent: Friday, 29 April 2005 10:01 AM
To: Paresh Khatri; Sheahan, John; ccielab@groupstudy.com
Subject: Re: EIGRP Composite Metric Calculation
Thanks for the help!
On R1, the delay for 172.16.1.0/24 is 1000ms, the bandwidth is 10000kb.
The outgoing interface on R2 is the same.
The network 172.16.1.0/24 is actually the Loopback interface 0 on R3. This
interface shows delay=5000ms and the bandwidth= 8,000,000kb.
----- Original Message -----
From: "Paresh Khatri" <Paresh.Khatri@aapt.com.au>
To: "Sheahan, John" <John.Sheahan@priceline.com>; <ccielab@groupstudy.com>
Sent: Thursday, April 28, 2005 7:19 PM
Subject: RE: EIGRP Composite Metric Calculation
> Hi,
>
> What does the output of 'sh ip eigrp topology 172.16.1.0 255.255.255.0'
indicate as the bandwidth and delay on R1 ?
>
> Paresh.
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
> Sheahan, John
> Sent: Friday, 29 April 2005 07:15 AM
> To: ccielab@groupstudy.com
> Subject: EIGRP Composite Metric Calculation
>
>
> I am trying to manually calculate the EIGRP Composite metric in a basic
> lab setup. My numbers aren't coming out to what the book says. I have
> three routers connected in togther in a row with the ethernet ports as
> follows:
>
>
>
> R1----------R2-----------R3
>
>
>
> R3 has a loopback address of 172.16.1.0/24.
>
>
> I notice that when I do a "show ip route 172.16.1.0" on R1, I see the
> reliability to this route as 131/255 and a metric of 435200 to that
> route.
>
> When I try and do the calculation for the composite metric (CM), I am
> getting the wrong answer and was wondering if I have to include the
> reliability (131/255) into my calculation?
>
> The formula I am using is:
>
>
> DELAY_sum = The sum of the delay on outgoing interfaces only to the
> destination route 172.16.1.0/24
>
> BW_min = 10 to the 7th power divided by the smallest bandwidth to the
> destination route 172.16.1.0/24
>
> CM = (256 x BW_min) + (256 x DELAY_sum)
>
> My calculations would be:
>
> CM = (256 x 10000) + (256 x 7000)
>
> CM = 4,352,000 which is off by one zero based on the metric of 435200
> reported by the R1 router.
>
>
> Can anyone give me a hint as to what I'm doing wrong?
>
> Thanks!
>
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