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Beginner

Ether-Channel LAN Speed

Hi 

Hope you all doing great,

 

i am using two switches one is 3560 and second one is 2950 for ether-channel i have tested all links by unplugging them ether-channel is working fine but the problem is its not making impact on LAN speed like both switches are 10/100 and i have 4 links in a bundle it should be now 400 mbps , before this ether channel i was getting 10 mb transfer rate from server (tested with ftp and also copied a folder by sharing) but after configuration the speed is same isn't it should be increase

kindly correct me if i'm wrong somewhere

 

Thanks & Best Regards:

HAMZA SHAHID

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Accepted Solutions
VIP Expert

Re: Ether-Channel LAN Speed

You're likely looking at "Marketing" or "Sales" links. It's as the others have noted, a single flow will only use one link, so one flow will never obtain more bandwidth then one link's worth. As also mentioned by another poster, using the wrong hashing algorithm, or just not having one suitable for your traffic will send ALL traffic to just one link (then you obtain no additional bandwidth, but your do still gain redundancy). Lastly, even in an "ideal" situation, multiple flows might map to the same link as Etherchannel does not take into account link loading, so you often will not obtain all the possible bandwidth. For example, if you have a dual link Etherchannel, the second flow has a fifty/fifty chance of being sent to the link being used by the first flow, so instead of gaining twice the bandwidth (on average) you'll only gain another fifty percent.

6 REPLIES 6
VIP Advisor

Re: Ether-Channel LAN Speed

Hi there,

An etherchannel performs per-flow load balancing. This means the load balancing algorithm balances multiple flows across the member links, but each flow only uses one link, so the maximum speed of a flow is determined by a single link, not the aggregate speed of all the member links.

Having multiple member links reduces the possibility of congestion occurring due to multiple flows.

 

It is worth pointing out thew there are typically several hashing algorithms available which depending on your topology and source-destinations can give more optimal flow distribution across member links.

 

cheers,

Seb.

Highlighted
Beginner

Re: Ether-Channel LAN Speed

but then why all says all links add up to become one link and their bandwidth too and i have seen all figures in many tutorials they also mentioned 100 mbs link becomes 800 when 8 links bundled

Kindly explain if possible

VIP Mentor

Re: Ether-Channel LAN Speed

Its one logical bandwidth pipe but still 4 physical links , you would never get the same speed from say a 4 x 10Gb compared to an actual 1 physical 10Gb link , bandwidth and speed are separate , you can alter flows though as Seb has stated and etherchannel has a lot of benefits for HA
Rising star

Re: Ether-Channel LAN Speed

the word "flow" may need some explanation.

 

when having your switch uplink combined in an etherchannel of multiple ports, does improve the maximum usable bandwith,

but not for a single "flow" which is an ip-address/port communication between host1 and host-2

this still maxxes to a single port-speed.

but simultanuous   you can start a second flow over the etherchannel between host 3 and 4

this flow well be sent using another port in the etherchannel

this way multiple flows can add up to more than a single port-speed.

 

like it is also common to call a 100Mbps full-duplex connection  200Mbps bandwith ,

each direction still maxes out to 100Mbps. but sending data in both directions will exceed 100Mbps.

 

VIP Expert

Re: Ether-Channel LAN Speed

You're likely looking at "Marketing" or "Sales" links. It's as the others have noted, a single flow will only use one link, so one flow will never obtain more bandwidth then one link's worth. As also mentioned by another poster, using the wrong hashing algorithm, or just not having one suitable for your traffic will send ALL traffic to just one link (then you obtain no additional bandwidth, but your do still gain redundancy). Lastly, even in an "ideal" situation, multiple flows might map to the same link as Etherchannel does not take into account link loading, so you often will not obtain all the possible bandwidth. For example, if you have a dual link Etherchannel, the second flow has a fifty/fifty chance of being sent to the link being used by the first flow, so instead of gaining twice the bandwidth (on average) you'll only gain another fifty percent.

Beginner

Re: Ether-Channel LAN Speed

Thanks all for your precious explanation and clearing concept i have another question but first i will check post if not found then will post my question to clear my concept because i have not found any tutorial on that.
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