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Author Topic: MLT and Stacked Switches  (Read 2924 times)

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Offline budaboy

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MLT and Stacked Switches
« on: October 13, 2014, 09:41:49 AM »
Hi Guys,

I was hoping I might be able to ask a question and then pose a possible network design for your evaluation.

Ok, is it possible to create an MLT using ports on different switches if those switches are in a stack?

Now, if that is possible, would my attached network diagram be the most efficient way to connect my network?

If it is not clear from my diagram each line on the MLT is connected to a different switch as opposed to the stack as a whole.

Any suggestions or comments would be greatly appreciated.

Kind regards
Andrew


Offline pat2012

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Re: MLT and Stacked Switches
« Reply #1 on: October 13, 2014, 09:24:49 PM »
Hello budaboy.

As for your first question. It is quite possible and is actually a recommended practice to create an MLT using ports on different stacked switches.  In this case it would be referred to as a DMLT - Distributed MLT.

You did not mention the model of the switches - in particular the core switch. Technically your design will work but as for it being the most efficient.... It may depend on what you have at the core.

Offline Dominik

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Re: MLT and Stacked Switches
« Reply #2 on: October 14, 2014, 02:35:48 AM »
Your design would work, from a redundancy prospective I would recommand to use a switchcluster in the core instead of one big stack.

If your central stack has a problem your complete network is down.
With a switchcluster you have two idenpendent switches wich can from a multichassis link aggregation for your access switches across two independent hardwre devices.
There are some benefits that you get with a switchcluster layout, active/active loadbalancing for L3 routing,
in service software update, more resiliant redundancy .

So a big stack as a core is possible , but recommanded is a switchcluster in the core.

Cheers
Itīs always the networks fault!
networkautobahn.com

Offline budaboy

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Re: MLT and Stacked Switches
« Reply #3 on: October 14, 2014, 05:55:56 AM »
Hi Pat2012,

Your quite right, I should have explained what model of switches I have. Ok currently I have 2x Nortel 1612G firbe switches acting as the core and Nortel 5520's and 5510's to service end user device. I think my current core switches may have a configuration similar to the one Dominik is describing, but I would actually know how to check for definately or how it was actually setup. The one thing I do know is that they both have virtual IPs for the gateway, so both should be able to route traffic between vlans.

However, my issue as it stands it that there is only 1Gb worth of bandwidth between each cab and this is causing things like imaging to take longer than I would like when multiple machines are being imaged. Now, would it be better to utilise the Nortel 1612G's instead of creating a switch cluster? Then just utilise more links out the cabinets?

Also, how would I create a switch cluster?

Regards

Andrew

Offline Dominik

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Re: MLT and Stacked Switches
« Reply #4 on: October 14, 2014, 09:05:33 AM »
With your current ERS1612 and ERS55xx you can trunk up to 8 Links togehter to increase the bandwith.
Here you have the limition that you have only 12 Ports available on your ERS1612.
So for example you can build up a 8 Port MLT trunk at one of your access swicthes and patch 4 of these Links to each of your ERS1612. There you would have to configure a SMLT assuming you have already setup an switchcluster /IST on your ERS1612.
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Offline budaboy

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Re: MLT and Stacked Switches
« Reply #5 on: October 14, 2014, 09:59:29 AM »
Hi Dominik,

As I said, I think one may be in place already. However my problem is that the vlans created on my network do not take advantage of our whole IP range and I don't feel we are getting the best throughput available for the kit we have.

So how would I check if I currently have a switch cluster setup?

And how would a go about creating a new one if needs be?

Offline Dominik

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Re: MLT and Stacked Switches
« Reply #6 on: October 14, 2014, 11:17:35 AM »
With the commands :
show ist
show smlt

you can check the current status.
When the output shows enabled yes and running yes, you already have a switchcluster that is running.

Here is a link to blog post from Michael that shows all the needed steps to set up an switchcluster:
http://blog.michaelfmcnamara.com/2011/12/avaya-split-multilink-trunking-smlt-layer-2-trunking/
Itīs always the networks fault!
networkautobahn.com