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Fibre Channel (SAN)

New Contributor
Posts: 2
Registered: ‎04-12-2017

Decommission ISL ports between a fabric


We have two 5300 switches, running FOS 7.2.1d  in a fabric, which are linked across site via DWDM ISLs and would like to remove the inter site connectivity. As we have production servers connected to the seperate switches and would want to complete this without any interuption to the service.


I noticed the following the the FOS 7.2 guide

The following restrictions apply to port decommissioning:

. • Port decommissioning is not supported on ports with DWDM, CWDM, or TDM


So is there a command line procedure to remove these ports and return them to normal host connected ports without downtime. Just concerned that the switches might lose there zoning configuration



New Contributor
Posts: 2
Registered: ‎04-12-2017

Re: Decommission ISL ports between a fabric

From further reading .... Would this be correct?


The customer currently has multiple Brocade 5300 fabrics, which are linked across site via DWDM ISLs. Due to the ongoing costs of the inter site connectivity, it has been decided to decommission the ISL ports which were originally used to connect Netapp Metro-Clusters. 


From experience, the best way forward would be to physically remove the SFP from the ISL port on the sub-ordinate switch first (switchshow lists the switchRole:). When the ISL is removed from the sub-ordinate or slave switch, it will automatically become a principal in its own right as it assumes the path to the principal has been lost. At this stage you can then re-configure the port, remove or add local zoning. Should you need to revert the configuration on the sub-ordinate switch, that’s assuming no zoning configuration has been applied, then you just need to re-install the SFP’s to the port. However, if any zoning or changes have been applied then you would need to first delete the zoning configuration, (as the Principal would need to write the master configuration to switch) which would require shutting down host connectivity and then reconnect the ISL links and let the principal upload the configuration back.

Overview of ISL decommission:

  • run a local configupload to a local ftp server
    • This will ensure you have a local copy of the zoning configuration, should the configuration need to be re-applied to the switch
  • remove the SFP from the ISL ports
    • Remove the sub-ordinate SFP connection first (
  • run the following commands to check status
    • switchshow – check that the switchrole is now Principal
    • alishow – displays zoning configuration

Revert decommissioned ISL configuration on sub-ordinate switch:

  • If no changes have been made then re-add the SFP’s
    • run switchshow to see whether switch has now adopted the sub-orinate role
  • Changes have been applied, switch will need to be
    • Power off any hosts connectivity to the sub-ordinate switch
    • plugin the ISL links
    • switchdisable
    • cfgdisable
    • cfgclear
    • cfgsave
    • Plugin ISL links
    • switchenable

The switch will merge back into the fabric and should not be segmented.

Broadcom Moderator
Posts: 467
Registered: ‎03-29-2011

Re: Decommission ISL ports between a fabric



To decomission the ISL, I would briefly proceed as follows


0. run a configupload and supportsave on both switches (captures all settings including zoning).


1. verify that no ongoing zoning transaction in the fabric with cfgtransshow


2. if you have more than one switch in the new fabrics, then selecting / setting fabric principal settings (in case you only have two switches in total, so nothing to do really).


3. disable the port on both side persistently - portcfgpersistentdisable


4. then run the switchshow, nsallshow, nssshow to determine status on both side


5. unplug SFP / cables


In your case, portdecom do not apply since you are running over a DWDM and also since you cannot portdecom the last ISL between to domain.



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Any and all information provided by me is not reviewed, approved or endorsed by Brocade and is provided solely as a convenience for Brocade customers. All systems and all networks are different and unique. If you have a service affecting network problem, please open a TAC service request for service through Brocade, or through your OEM equipment provider. If this provided you with a solution to this issue, please mark it with the button at the bottom "Accept as solution"

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