Re: EIGRP Traffic Share Count

Hi Paul,

Thanks I am still a little confused about how we managed to get the value of 61 from the metrics?

Sent from my iPad

On 27/09/2010, at 11:02 AM, Paul Negron <negron.paul_at_gmail.com> wrote:

> Fellas,
>
> First of all. Make sure you change the delay for the interface to be 10 if
> you are using dynamips. Yes, it is off.
>
> If you were to take 4 paths with the following bandwidths:
>
> 1 = 100K
> 2 = 200K
> 3 = 300K
> 4 = 400K (This being the best path)
>
> After configuring a variance of 4:
>
> The following metrics would be used:
>
> 1 = 6530560 traffic-count = 240
> 2 = 8663808 traffic-count = 181
> 3 = 12930560 traffic-count = 121
> 4 = 25730560 traffic-count = 61
>
>
> What Garth said takes over from here:
>
> Largest metric (25730560) divided by path 1 metric (6530560) = 3.94002352
> Therefore the traffic-share of path 4 (61) * 3.94002352 = 240.341
> rounded down to the nearest integer is 240.
>
> Largest metric (25730560) / path 2 metric (8663808) = 2.969890376
> Therefore the traffic-share of path 4 (61) * 2.969890376 = 181.16
> rounded down to the nearest integer is 181.
>
> Largest metric (25730560) / path 3 metric (12930560) = 2.969890376
> Therefore the traffic-share of path 4 (61) * 1.98990299 = 121.38 rounded
> down to the nearest integer is 121.
>
> Largest metric (25730560) / path 4 metric (25730560) = 1
> Therefore the traffic-share of path 4 (61) * 1 = 61 rounded down to the
> nearest integer is 61.
>
> Sure enough, I tested this by turning off CEF and I observed 240 packets
> down PATH 4 , 121 packets down path 3 and so fourth.
>
> This is how it works Gentlemen.
>
> Paul
> --
> Paul Negron
> CCIE# 14856 CCSI# 22752
> Senior Technical Instructor
> www.micronicstraining.com
>
>
>
>> From: Bilal Hansrod <bilal.hansrod_at_gmail.com>
>> Reply-To: Bilal Hansrod <bilal.hansrod_at_gmail.com>
>> Date: Mon, 27 Sep 2010 11:22:22 +1000
>> To: Garth Bryden <hacked.the.planet.on.28.8k.dialup_at_gmail.com>
>> Cc: Cisco certification <ccielab_at_groupstudy.com>
>> Subject: Re: EIGRP Traffic Share Count
>>
>> Sorry Garth, I didn't mean to confuse you, but waiting for big boys to come
>> up with logical explanation when they have time :-)
>>
>> Regards,
>>
>> Bilal H
>>
>>
>>
>>
>> On Mon, Sep 27, 2010 at 11:12 AM, Garth Bryden <
>> hacked.the.planet.on.28.8k.dialup_at_gmail.com> wrote:
>>
>>> Would be nice to find out why such the large values, I believe it is so it
>>> can get the share ratio as accurate as possible while using whole numbers,
>>> because the actual ratio is so close.
>>>
>>> Though, I always believed the traffic share count would always start at 1
>>> then the rest of the paths increased based on the ratio.. if the numbers
>>> where not whole numbers then it'd be rounded down to the whole number.. but
>>> based on that logic your traffic share count 1:1 not 103:120
>>>
>>> Though after googling to try find some information on it, I've come back
>>> with nothing and more confused than before!! There is a cisco press book
>>> "Traffic Engineering with MPLS" which is saying non-whole numbers are
>>> rounded UP to the nearest integer not rounded DOWN though all the Cisco
>>> Documentation says it is rounded down. :-/
>>>
>>> On Mon, Sep 27, 2010 at 8:44 AM, Bilal Hansrod
>> <bilal.hansrod_at_gmail.com>wrote:
>>>
>>>> Hello again,
>>>>
>>>> Garth has provided a valuable resource to calculate Traffic Share and
>>>> detail about load sharing. Can anyone else, please provide more
>>>> understanding on how to calculate share based on examples as I am having
>>>> difficulty understanding nuts and bolts of Traffic Share Count.
>>>>
>>>> Thanks everyone -
>>>>
>>>> Regards,
>>>> Bilal
>>>>
>>>> On Sun, Sep 26, 2010 at 11:42 PM, Bilal Hansrod <
>>>> bilal.hansrod_at_gmail.com> wrote:
>>>>
>>>>> Thanks Garth, but still I am trying to understand Traffic Share Count
>>>>> value arrived via calculation. How did you get 120 via 155.1.67.7 and 103
>>>>> via 155.1.146.1 (please see below output from show ip route 155.1.9.9).
>>>>> There is a lab in INE W1 and it asks to change the traffic share to 1:5
>> and
>>>>> uses the formula:
>>>>>
>>>>> INE Task 5.15 EIGRP Unequal Cost Load Balancing
>>>>>
>>>>> "These paths are now balanced 103:120. To achieve the desired 1:5 traffic
>>>>> share,
>>>>> R6s delay on the link to R1 must be updated. The actual values used on
>>>>> R1,
>>>>> R3, and R6 for delay can have multiple valid options as long as two
>>>>> conditions
>>>>> are true. First, the Advertised Distance R1 sends to R6 must be lower
>>>>> than R6s
>>>>> Feasible Distance. Secondly the entire composite result R6 calculates
>>>>> through
>>>>> R1 should be five times the Feasible Distance.
>>>>> In our case R1s Advertised Distance is 40 microseconds, or 4 tens of
>>>>> microseconds. This specifically means the following must be true if we
>>>>> want a
>>>>> traffic share of 1:5.
>>>>> 3072 * 5 = (R6_TO_R1_DLY + 4) * 256
>>>>> Therefore R6s delay to R1 should be 56 tens of microseconds."
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> On Sun, Sep 26, 2010 at 10:29 PM, Garth Bryden <
>>>>> hacked.the.planet.on.28.8k.dialup_at_gmail.com> wrote:
>>>>>
>>>>>> Hi Bilal,
>>>>>>
>>>>>> You want to read this post-
>>>>>>
>> http://blog.ine.com/2009/05/01/understanding-unequal-cost-load-balancing/..
>>>>>> This has an explanation on the traffic share ratio you are seeing above.
>>>>>>
>>>>>> I think the answer you seek though is
>>>>>>
>>>>>> EIGRP will divide each links metric by the largest paths metric..
>>>>>>
>>>>>> 3584 / 3072 which is 1.166
>>>>>> 3584 / 3584 which is 1
>>>>>>
>>>>>> FYI- 120 / 103 = 1.165
>>>>>>
>>>>>> EIGRP will round down to the nearest integer so the first path is
>>>>>> actually "1"
>>>>>>
>>>>>> I also believe the largest metric would have be a path being selected by
>>>>>> EIGRP for placement into the routing table.. If your route is not
>> selected
>>>>>> because the metric is larger than the
>>>>>> Variance x feasible distance.. I do not believe it will be included in
>>>>>> the route traffic share calculation.
>>>>>>
>>>>>> HTH
>>>>>>
>>>>>> Garth
>>>>>>
>>>>>>
>>>>>>
>>>>>> On Sun, Sep 26, 2010 at 6:14 PM, Bilal Hansrod <
>>>>>> bilal.hansrod_at_gmail.com> wrote:
>>>>>>
>>>>>>> Hello Everyone,
>>>>>>>
>>>>>>> I am having difficulty calculating the EIGRP Traffic Share Count. As
>>>>>>> far as
>>>>>>> my understanding regarding Traffic Share Count is, you divide the
>>>>>>> largest
>>>>>>> metric with lowest to forward packets based on number. For example
>>>>>>>
>>>>>>> A-X = Metric is 10
>>>>>>> B-X = Metric is 20
>>>>>>> C-X = Metric is 30
>>>>>>> D-X = Metric is 40
>>>>>>> E-X = Metric is 90
>>>>>>>
>>>>>>> If I configure variance 4, it means all above metric will be used for
>>>>>>> load
>>>>>>> balancing except E-X (90), because it does not fall under 80 (Lowest
>>>>>>> Metric
>>>>>>> X 4). So when calculate, I still use E-X Metric for Traffic Share
>>>>>>> Count.
>>>>>>>
>>>>>>>
>>>>>>> A-X = Metric is 10 = Traffic Share Count (90/10) = 9
>>>>>>> B-X = Metric is 20 = Traffic Share Count (90/20) = 5
>>>>>>> C-X = Metric is 30 = Traffic Share Count (90/30) = 3
>>>>>>> D-X = Metric is 40 = Traffic Share Count (90/40) = 2
>>>>>>>
>>>>>>> It means 9 packets will be sent via A-X, 5 packets via B-X, 3 packets
>>>>>>> via
>>>>>>> C-X, and 2 packets via D-X and round robin. Am I correct till here??
>>>>>>>
>>>>>>> Now, when I have below output, how is Traffic Share Count calculated
>>>>>>>
>>>>>>> Rack1R6#show ip route 155.1.9.9
>>>>>>> Routing entry for 155.1.9.0/24
>>>>>>> Known via "eigrp 100", distance 90, metric 3072, type internal
>>>>>>> Redistributing via eigrp 10, eigrp 100
>>>>>>> Advertised by eigrp 10
>>>>>>> Last update from 155.1.146.1 on FastEthernet0/0.146, 00:01:04 ago
>>>>>>> Routing Descriptor Blocks:
>>>>>>> 155.1.146.1, from 155.1.146.1, 00:01:04 ago, via FastEthernet0/0.146
>>>>>>> Route metric is 3584, traffic share count is 103
>>>>>>> Total delay is 140 microseconds, minimum bandwidth is 1544 Kbit
>>>>>>> Reliability 255/255, minimum MTU 1500 bytes
>>>>>>> Loading 1/255, Hops 4
>>>>>>>
>>>>>>> * 155.1.67.7, from 155.1.67.7, 00:01:04 ago, via FastEthernet0/0.67
>>>>>>> Route metric is 3072, traffic share count is 120
>>>>>>> Total delay is 120 microseconds, minimum bandwidth is 100000 Kbit
>>>>>>> Reliability 255/255, minimum MTU 1500 bytes
>>>>>>> Loading 1/255, Hops 2
>>>>>>>
>>>>>>>
>>>>>>> Anyone's help will be highly appreciated,
>>>>>>>
>>>>>>> Regards,
>>>>>>>
>>>>>>> Bilal
>>>>>>>
>>>>>>>
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Received on Mon Sep 27 2010 - 12:13:24 ART