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November 17th, 2015 03:00

Difference between ISL and trunking


We have 2 X 24 port DS 300B switches and looking to upgrade the port with 48 ports.

Can we make the old 2 X 24 port switch as one switch with 48 ports and ISL ?

I believe we need to have ISL for trunking.

Should we need trunking license for ISL if i don't need any link aggregation  and all?

Thanks in Advance ,

Muhammed Basheer MP

195 Posts

November 17th, 2015 07:00

You can do what you outlined, and you do not need a trunking license to do it.

A couple of things:

>  If there are active zonesets in the old switches they will be merged when the switches are connected.  You may want to clear the zonset from one of them to avoid this.

>  Each ISL will occupy a port on each switch, so for instance, if you use four ISLs then your 2 x 24 port switches will only net 40 open ports.

>  You will want to monitor utilization of your ISLs to insure that you have enough of them to avoid bottlenecks.

>  As a tip, you may want to insure that your most important traffic between hosts and storage does not go over the ISLs by keeping those things on ports that are on the same switch.

>  Trunking would better optimize and balance the ISLs, but it is not a requirement.

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