Home > Networking Solutions > Converged and Hyperconverged Solutions > VxRail Networking Solutions > Guides > Dell EMC Networking SmartFabric Services Deployment with VxRail 4.7 > Verify preferred master setting before fabric expansion
During fabric expansion, newly added switches may come up and form a fabric among themselves and elect a master before they are connected to the existing fabric. When the new fabric merges with the running fabric, it is possible for the master switch from the new leaf switches to overwrite the configuration in the existing fabric. Therefore, it is critical to ensure a pair of leaf nodes in the existing fabric are configured to be the "preferred master" before expanding the fabric.
When you create an uplink to the external network using the SFS GUI or OMNI, the preferred master is automatically set on all leaf switches in the fabric at that time.
Note: Spine switches are never elected SmartFabric master or preferred master switches.
Before connecting additional leaf switches to the fabric, verify the preferred master is set on at least one pair of leaf switches currently in the SmartFabric. This is done by running the show smartfabric cluster command on each leaf in the existing fabric.
The output for at least one pair of leaf switches in the SmartFabric must show PREFERRED-MASTER is set to true. The following commands and output are from Leaf1A and Leaf1B:
S5248F-Leaf1A# show smartfabric cluster
----------------------------------------------------------
CLUSTER DOMAIN ID : 100
VIP : fde2:53ba:e9a0:cccc:0:5eff:fe00:1100
ROLE : MASTER
SERVICE-TAG : 690ZZP2
MASTER-IPV4 : 100.67.166.27
PREFERRED-MASTER : true
----------------------------------------------------------
S5248F-Leaf1B# show smartfabric cluster
----------------------------------------------------------
CLUSTER DOMAIN ID : 100
VIP : fde2:53ba:e9a0:cccc:0:5eff:fe00:1100
ROLE : BACKUP
SERVICE-TAG : 68X00Q2
MASTER-IPV4 : 100.67.166.27
PREFERRED-MASTER : true
----------------------------------------------------------
For the example in this guide, there are only two leaf switches in the SmartFabric at this stage of deployment. However, if there were additional leaf switches in the SmartFabric when the uplink was created, they would also show PREFERRED-MASTER is set to true.
If the fabric was previously expanded after the uplink was created, the added leafs would not have PREFERRED-MASTER set to true. This is okay as long as PREFERRED-MASTER is set to true on at least one pair of leaf switches currently in the SmartFabric.
Note: This section only applies if there are no leaf switch pairs in the SmartFabric with PREFERRED-MASTER set to true. If this does not apply, skip to Check preferred master status on new leafs.
If no leaf switch pairs in the existing SmartFabric show PREFERRED-MASTER set to true, create an uplink by following the instructions in Configure L2 uplinks to the external network or Configure L3 routed uplinks to the external network. After the uplink is created, return to the preceding section and check the preferred master setting again.
If you are using a demo or lab environment without the need for an uplink, create a temporary uplink to set all leaf switches currently in the SmartFabric to be the preferred master.
Note: No physical port connections are required to create this temporary uplink.
Create a temporary uplink as follows:
Note: You will not be able to use this interface for other purposes until you delete the uplink.
After the uplink is created, verify all leaf switches in the SmartFabric show PREFERRED-MASTER is set to true.
To make the interface used in the temporary uplink available for other purposes, you can delete the uplink without affecting the preferred master setting. This is done as follows:
The port used for the temporary uplink is now available.
Run the show smartfabric cluster command on each leaf switch to be added to the SmartFabric and ensure none show PREFERRED-MASTER set to true. These switches should still be in their factory default mode, Full Switch mode, and the command and output should appear as follows on each switch:
OS10# show smartfabric cluster
----------------------------------------------------------
CLUSTER DOMAIN ID :
VIP : unknown
ROLE : unknown
SERVICE-TAG : unknown
MASTER-IPV4 :
PREFERRED-MASTER :
----------------------------------------------------------
If any leaf switch to be added to the SmartFabric shows PREFERRED-MASTER is set to true, the switch configuration should be cleared. This is done by taking each affected leaf switch out of SmartFabric mode and returning to Full Switch mode with the following commands:
OS10# configure terminal
OS10(config)# no smartfabric l3fabric
Reboot to change the personality? [yes/no]:y
After the switch reloads, run show smartfabric cluster again on each affected leaf switch to confirm PREFERRED-MASTER is no longer set to true.
Note: New switches will be placed in SmartFabric mode in the Add switches to SmartFabric section of this chapter.