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Difference in behaviour between seperate ISL and ISL trunks

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  • 1.  Difference in behaviour between seperate ISL and ISL trunks

    Posted 02-08-2016 07:43 AM

    Hi all,

     

    What we are lookig for is a document (ideally a table) that shows at a glance the differences in beheviour and characteristics if someone were to use standard ISLs vs an ISL trunk.

    Say for example we had 2 switches and we could either join them via 4 seperate ISLs or we could use trunking to merge those 4 ISLs into one link what would the differences in throughput patterns, failover, physical link utlisations etc be?

    We would like to understand if the cost of new trunking licenses are worth it and how the links will behave with and without trunking.

     

    Thanks for any help.


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  • 2.  Re: Difference in behaviour between seperate ISL and ISL trunks

    Posted 02-09-2016 05:00 AM

    Hi, then you use ISL connection without trunking, you must remember about dls option.

    And a problem with latency at connect, reconnect or disconnect one of several ISL links.


    #BrocadeFibreChannelNetworkingCommunity


  • 3.  Re: Difference in behaviour between seperate ISL and ISL trunks
    Best Answer



  • 4.  Re: Difference in behaviour between seperate ISL and ISL trunks

    Posted 04-20-2016 12:55 AM

    The most important part for me has always been the impact on the fabric when a link goes offline. If you have 4 isolated ISL's a link-drop has an immediate effect on fabric operations as FSPF routes have to be recaculated. If a trunk-member link fails there is only a re-balance of traffic on the ASIC driver level but does not impact fabric behaviour as such.

     

    I would use trunks if I where you.


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  • 5.  Re: Difference in behaviour between seperate ISL and ISL trunks

    Posted 05-17-2019 05:46 AM
    What kind of impact do you mean? data loss or something?
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  • 6.  Re: Difference in behaviour between seperate ISL and ISL trunks

    Posted 30 days ago

    With fibre channel both links would be available.

     

    If you also happen to use Exchange-Based Routing Protocol the (most likely SCSI) exchanges will be load-balanced between the members of a trunk. If you use port-based then it would be good for utilization purposes to also enabled DLS - dynamic link sharing. See output of "aptpolicy" for which is configured (this can be different between switches).

     

    Trunking also provides some protection. If a member in a trunk gets disconnected your servers shouldn't notice anything.


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  • 7.  Re: Difference in behaviour between seperate ISL and ISL trunks

    Posted 30 days ago

    Not sure what has prompted the recent responses to this question but it was originally posted in 2016 and does not require answering!

     

    Thanks.


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