FabricOS : Warning port 0, domain IDs overlap on Brocade FC

By | May 17, 2016

As you probably wanted to extend your Brocade fiber channel fabric by connecting your existing switch to a new one, you probably noticed the following behaviour :

1. The port is blinking (green light)
2. The following message can be shown in the event log : Warning port 0, domain IDs overlap. Switch 19 1 FABR-1001 FCfabric-SW01

This is happening because the new switch have the same “Domain ID” as the existing one. In order to “extend” your existing switch, you have to set a different domain ID on the second switch.

You also need the “Fabric license” on both switches and the new switch should have no zoning configuration present.

Follow this procedure to proceed with this configuration (on the second, new switch) :

1. Disable the switch :


2. Enter in the configuration prompt :


You will be prompted for (just say “y”) :

Fabric param (yes, y, no, n): [no] y

And the domain ID will be requested (just enter the domain ID) :

Domain: (1..239) [1] 2

Then you can skip further steps by issuing CTRL+C or continue if you did not configured the switch yet. Once completed, enable the switch :


NOTE : Depending on the traffic that might be exchanged between both physical units, you need to do proper capacity planning to determine how many ports should be used as uplinks (we refer as ISL – “Inter-Switch Links” in the storage network language). A minimum of two would be recommended, both for capacity and redundancy. You can use as many port as needed (up to 8) for this purpose, no specific configuration needed since the system will recognize the topology and mark and use them as “upstream” ports.