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New Member

Load sharing

Hi Experts,

I have two switches A and B interconnected with two uplinks.Each switch has only one PC connected to it. Do we have any options to share the load (50 - 50) between the uplinks..

Host1-Switch A ---------- Switch B - Host2

                        ----------   

Thanks,

Arun

5 REPLIES
New Member

Load sharing

Hi Arun,

Not sure which switches  you are using. You can bundle the uplinks in a etherchannel if they are of the same capacity. Loadbalancing cant be achieved, the load will be shared across the links if the traffic is from different source and destination.

Regards,

Sathvik K V

Silver

Load sharing

What platform is this?

Like Sathvik said, your best bet is to form an Etherchannel. However since you have only one host on each side the communication will only use one pair of source and dest MAC and source and dest IP. This means that the same outgoing link would always be chosen for communication between these hosts.

If the platform supports it the hashing algorithm can use L4 port information for the hashing decision. This would at least share traffic across links if you have different flows between the hosts. The share would depend on how much traffic each session is generating and you would probably never achieve a 50-50 split.

Daniel Dib
CCIE #37149

Please rate helpful posts.

Daniel Dib CCIE #37149 Please rate helpful posts.
Super Bronze

Re: Load sharing

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

As the other posters have noted, if source and destination attributes are the same, for Etherchannel, the same link will be used.  As Daniel noted, some (often the higher end models) switches, within their hashing algorithm choices, also support L4 ports, but unless ports differ between flows, again the same link will be used.

If your hosts can be multi-homed, i.e. multiple IPs, that could allow different flows to use a different Etherchannel link.

Something to also keep in mind, Etherchannel doesn't do dynamic load balancing.  Even if you have different attributes, multiple flows can be sent to the same link.  For example, first flow saturates one link.  Second flow, is "sent" to the same, already saturated, link, while second link is unused.

When possible, "faster" link is often the better solution (this is one reason why often uplinks ports have higher bandwidths).

If you're using routers, rather than switches, something like OER/PfR can dynamically load balance across your links.

New Member

Load sharing

Hi Arun,

As Joseph said OER/PFR is the best solution if you are using routers.

Joseph,

I'm asking you out of  this thread  which is the best IOS you would suggest for PFR.

Routers : 7600,3845,7200

Regards,

Sathvik K V

Super Bronze

Re: Load sharing

Disclaimer

The  Author of this posting offers the information contained within this  posting without consideration and with the reader's understanding that  there's no implied or expressed suitability or fitness for any purpose.  Information provided is for informational purposes only and should not  be construed as rendering professional advice of any kind. Usage of this  posting's information is solely at reader's own risk.

Liability Disclaimer

In  no event shall Author be liable for any damages whatsoever (including,  without limitation, damages for loss of use, data or profit) arising out  of the use or inability to use the posting's information even if Author  has been advised of the possibility of such damage.

Posting

Haven't used PfR on 7600 series; good chance support for it is very limited on that platform.

For 3845 and/or 7200, you might try (latest) 12.4(24)T#.

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