Etherchannel ====> Not answered yet, I accidently clicked on "correct answer"

[Kuldeep singh]

Only Experts,

This is sample diagram only for asking question:

These are in an Ether channel and each ports have 100 Mbps Speed.

1. How much speed or bandwidth i will get through this i.e 300 Mbps  OR  600 Mbps ?

(I am confused with this concept bcoz i read out many posts and Everywhere explained

with different different ways, somewhere says it is 300 or somewhere says 600 with Full-Duplex)

                                              AND

What does mean of this URL Explanation (will speed depends upon no of Port and ratio)

Does Etherchannel provides Link aggregation or not ? Bcoz Load balancing is different

thing. I am talking about only only only for Link aggregation or combination.

http://www.cisco.com/en/US/tech/tk389/tk213/technologies_tech_note09186a0080094714.shtml

Number of Ports in the EtherChannel	Load Balancing
8	1:1:1:1:1:1:1:1
7	2:1:1:1:1:1:1
6	2:2:1:1:1:1
5	2:2:2:1:1
4	2:2:2:2
3	3:3:2
2	4:4

2.  Which exact Command or Method to check Etherchannel total merged Speed ?

Note:  Please unexperience holder members do not reply me

[inayathulla1 · Accepted solution]

Hi Kuldeep,

You would diffenetly getting answer from expert soon on this.

But just to brief you about the Etherchannel or the question which you are asked for is:

a) Etherchannel is not load balancing its does the load sharing.

b) Coming to the dragram you have two switches connected with 3- 100 Mbps Speed links hence the total bandwidth will be 300 and not 600.

(Dont get confuse with half duplex or full duplex that doesnt come into picture).  Speed,duplex settings,link comes into picture to bundle the links into one channel.

c) Last but least on Etherchannel is that you cannot guarantee that each packet takes different link  at each time. Its all bases on the XOR algorithm.  But you have the option to use or make use of all 4 links based on the algorithm configured.

Hope this helps.

Regards

Inayath

[Giuseppe Larosa · Accepted solution]

Hello Kuldeep,

it is not the case to ask someone to remove useful answers from your thread.

You are not getting other answers because your questions are already answered well specially by Peter.

I just want to recap some info

>> 1. How much speed or bandwidth i will get through this i.e 300 Mbps  OR  600 Mbps ?

network engineer answer : you get 300 Mbps of aggregate bandwidth per direction (TRUE)

marketing answer: you get 300+300 = 600 Mbps of bandwidth  (technically FALSE)

Load balancing is flow based not per packet, so a single flow identified according per the load balancing algorithm will use a SINGLE member link. So the max speed for a single flow is 100 Mbps per direction not 300 Mbps.

Statistically multiple flows may be mapped to different member links providing a load sharing function.

Let's expand the mapping function shown in the table you have reported.

The mapping function works in the following way:

let's suppose that the algorithm in use is source-dest-IP the operation performed is an EXOR of last meaningful 3 bits of IP source address EXOR  last three bits of IP destination address.

The result of the operation is a binary number between 000 and 111.

The mapping function is a function of the algorythm in use (that decide what to check) and of the number of active member links in the bundle.

the member links are indexed from 0 to N-1  from 0 to 2 in your case

The mapping action can be represented as a table

Example for 3 link bundle:

EXOR result            link index

000                          0

001                          1

010                          2

011                          0

100                          1

101                          2

110                          0

111                          1

the end results is that of the 8 possible EXOR values 3 are mapped to link 0, 3 are mapped to link 1 and only 2 are mapped to link 2.  This is represented in the table in the Cisco document  as 3:3:2 as a short form notation.

This is the reason why it is recommended to use 2,4 or 8 member links to achieve better load balancing.

To be noted more powerful and modern switch platforms can use different algorithms on different type of traffic being able to use src-dest-IP for IPv4 traffic src-dest-MAC for non IP traffic and may be to recognize MPLS traffic. (C6500 just to be clear)

So in real world it would be better to add a fourth fast ethernet.

Member links have to be of the same speed, same duplex, same L2 settings ( same switchport type, if type is trunk the list of allowed vlans has to be identical, same STP settings).

Just to note L3 etherchannel can be confiigured in this case member links have no switchport + no ip address in configuation.

Link Aggregation is the standard term and actually even if etherchannel has been originated within Cisco, LACP is standards based and allows for multi vendor multi link interconnections 802.1AD is the standard then moved to 802.3AD.

So yes etherchannel is a form of link aggregation.

Edit:

there is no command that tell you the speed of the bundle as it is a function of traffic variety (number of distinct flows, traffic volume of each flow)

You need to keep an eye on usage of each member link.

It is possible to have one member link saturated and another link with 50% of utilization as it is traffic dependent.

From a design perspective we assume the speed to be that of the sum of member links.

Also the load balancing algorithm can be different at the two ends of the same bundle in order to achieve better load distribution

Hope to help

Giuseppe

[Kuldeep singh]

Hi Giuseppe,

Thanks for Reply...

Actually i said to inayath to remove his responses bcoz my this post was showing "correct answer"

bcoz it accidently clicked and i can not change status from my end.

One more question, what is benefit of Link aggregation with etherchannel, if we

talk about below diagram. If PC1 user send data to PC2 user then it will work

only on 100 mbps bcoz PC1 and PC2 connected to Single fastethernet port ?

is it possible to PC1 send data to PC2 with 300 mbps speed?

I think it is used only for redundancy and Load balancing not for Link

aggregation in my case..

am i right ?

[Giuseppe Larosa]

Hello Kuldeep,

threads are not closed in CSC even if you mark an answer as resolved, as you can note we both could add posts to the thread.

Regarding your last question traffic between PC1 and PC2 will be limited to 100 Mbps for two reasons:

a)  user facing interface is 100 Mbps

b) only one member link is used (at least with default load balancing methods) as traffic will be classified as single flow

However, if there are 50 PCs connected on one switch and other 50 PCs connected to the other switch you will likely use all three member links when these end user devices talk to each other.

Hope to help

Giuseppe

[Kuldeep singh]

Hi Giuseppe,

If we talk about concept of Link aggregation only, then where is the main role of

this Link Aggregation, only between Switch to Switch ?

[Giuseppe Larosa]

Hello Kuldeep,

link aggregation is not limited to switch to switch, often modern powerful servers are connected with a bundle to a single switch

Example:

server hosting multiple VMware instances has multiple GE NICs and can have 4 GE in bundles to switch1 and other 4 GE in bundles to switch2.

Both bundles are L2 trunk carrying multiple Vlans, each VMware instance uses a different MAC address and talk and receive in one or more Vlans.

Hope to help

Giuseppe

[Peter Paluch · Accepted solution]

Hello Kuldeep,

1. How much speed or bandwidth i will get through this i.e 300 Mbps  OR  600 Mbps ?

With  EtherChannels, you always have to keep in mind that a single stream  (i.e. a flow of data whose source MAC/IP/L4port, destination  MAC/IP/L4port) will be forwarded through a single link in this  EtherChannel. Therefore, a single stream will see no speed improvement  and will be limited to 100Mbps in one direction.

Different streams may be sent over different links, and in ideal case, the will be spread so that the aggregate amount of data carried in one direction is 300Mbps.

The 600Mbps is simply the aggregated  traffic in both directions. However, it is the same as if saying that a  single FastEthernet link will provide you with 200Mbps full-duplex.  Technically, the link still operates on 100Mbps - you just sum together  both directions. It has no big technical meaning but it looks good in  marketing materials

What does mean of this URL Explanation (will speed depends upon no of Port and ratio)

This  table tells you that even if the input streams to the switch are  perfectly balanced (the same amount of data, uniform distribution of  addressing information causing them to be otherwise evenly spread among  the ports in the EtherChannel), with 3 ports in your EtherChannel, one  port will be less utilized in the ratio of 3:3:2. For an even  distribution of traffic among your EtherChannel ports, you should use 2,  4 or 8 ports.

Does Etherchannel provides Link aggregation or not ?

It  does. Link aggregation is a general concept of utilizing parallel  interconnections between devices to increase the available bandwidth.  EtherChannel is a particular implementation of link aggregation by  Cisco.

2.  Which exact Command or Method to check Etherchannel total merged Speed ?

No  such command exists in my opinion. The true merged speed depends on the  amount of ingress traffic, traffic patterns, addressing information and  load balancing mechanism being used. What you only can check is the  momentary offered capacity by simply observing the counters on the  respective Port-channel interface.

Other friends are welcome to comment on this issue further!

Best regards,

Peter

[inayathulla1]

Hi Kuldeep,

Peter has clearly explained what you required. Let us know what exactly you are looking for? So tht we understand your requirement?

thanks

Inayath

[ALIAOF_]

3 x 100 Meg links, question is if you will get 300 Meg or 600 Meg, well the total bandwidth is 300 Meg however there are different ways load balancing works on the ether channels depending on how it is setup. 

Here is a decent explanation:

http://packetlife.net/blog/2010/jan/18/etherchannel-considerations/

Default method of load balancing is "src-mac".  So if a MAC of "xx:xx:xx:xx:xx:xa" sends something to "xx:xx:xx:xx:xz" over the first link all traffic will go over that link, but if there is another computer with a MAC of "xx:xx:xx:xx:xb" and sends something to "xx:xx:xx:xx:xz" it will go over the second link as the second one is free.  But the packets from the first one i.e; "xx:xx:xx:xx:xx:xa" will not spread accross 3 links.

Now there are some other methods too that will let you do it by the source IP, destination IP, Ports etc:

http://www.m00nie.com/2011/07/display-the-specific-port-used-in-an-etherchannel-for-given-srcdst-info/

Hope this helps