Connecting two SAN switches

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This is based on theoretical study. The steps have not been tested in lab or production.

The most common type of Fibre Channel SAN today is a switched fabric. Some common terms that are used when talking about a SAN are:

Node

'Node' is a server or a storage device.

Fabric

A 'Fabric' is the network that connects these nodes together, and includes the network switches.

Domain

A 'Domain' is a single switch within a fabric. A fabric can contain up to 239 domains, and in theory, the fabric can scale to about 16 million connections.

Refer: https://www.lascon.co.uk/SAN-switches-and-fabrics.php

1. For connecting two SAN switches ISL (Inter Switch Link) needs to be formed over E-port. Initiators and targets are connected to F-ports. Then both switches form a single fabric. In case of brocade command fabricshow would show only one fabric on both switches if connected properly via ISL.

   Refer:

   • https://community.brocade.com/t5/Fibre-Channel-SAN-Forums/Connect-host-to-storage-across-two-intermediate-switches/td-p/85665

2. Both the switches need to have exact same zoning configuration other wise they will not connect and single fabric will not form. For this one switch can have existing configuration but other should be blank. When a blank configuration switch is connecting to an existing SAN switch with configuration, the zoning configuration is automatically transferred and fabric is automatically formed.

   Refer:

   • https://community.brocade.com/t5/Fibre-Channel-SAN-Forums/Connect-host-to-storage-across-two-intermediate-switches/td-p/85665/page/2

3. Thus, steps are:
   1. disconnect all switches from each other.
   2. ensure that all switch IDs and domain IDs are different.
   3. clear config on the first switch and make the new zone configuration (for this particular switch).
   4. clear config on the second switch (totally clean, so there were no alises/zones/configs on it) and connect it to the first switch. Configuration merge happened, so the first switch and the second one have the same config.
   5. ensure that "fabricshow" shows the correct number of switches in the fabric (2 switches), ensure that "switchshow" shows no segmented entries, ensure that "cfgshow" on each switch shows the same configuration.

      This can be done for more than two switches also.

4. Domain ID (Referred in 3.b above) can be verified using "switchshow" command

   Refer:

   • https://community.brocade.com/t5/Fibre-Channel-SAN-Forums/How-to-connect-two-FC-Switches/td-p/28121
   • https://itknowledgeexchange.techtarget.com/itanswers/adding-two-addtional-san-switches-to-the-fabric/

5. Switch ID (Referred in 3.b above) should also be different

   Refer:

   • https://community.hpe.com/t5/EVA-Storage/connecting-two-SAN-switches-together-quot-how-to-configur-ports/td-p/3828513#.W_Z67pz-vak

6. Fabric license might be required in a few cases for fabric to be formed properly

   Refer:

   • https://community.brocade.com/t5/Fibre-Channel-SAN-Forums/How-to-connect-two-FC-Switches/td-p/28121
   • https://community.hpe.com/t5/EVA-Storage/Connect-two-SAN-switches/td-p/4721888#.W_Z3TZz-vak

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