During fabric expansion, newly added switches can come up and form a fabric among themselves, electing a leader before they are connected to the existing fabric. When the new fabric merges with the running fabric, it is possible for the leader switch from the new switches to overwrite the configuration in the existing fabric.
Therefore, it is critical to ensure that the preferred leader flag is set on at least one leaf or spine switch in the existing fabric before expanding the fabric to prevent configuration loss.
SFS sets the preferred leader flag automatically on all spine switches in the fabric when an uplink is created. If there are no spine switches, as in this example, the preferred leader is automatically set on both leaf switches in the fabric.
Check preferred leader status on existing leafs
To check the preferred leader flag, do the following:
- In the SFS UI, select the Switches tab.
- For the example in this guide, the preferred leader flag was automatically set on both leaf switches when the uplink was created. This is outlined in red in the figure below.
Set preferred leader if necessary
- Click the Preferred Leader toggle button next to the first switch that will be a preferred leader. Note: If spine switches are in the fabric, Dell Technologies recommends setting the preferred leader flag on all spines for best performance. If there are no spine switches in the fabric, Dell Technologies recommends setting the preferred leader on both leafs.
- Click OK. A Success message displays and the Preferred Leader toggle next to the switch is green, as shown.
- Repeat steps 1 and 2 for the second leaf switch, or for the remaining spines if applicable.
Optionally, the preferred leader flag may be verified at the CLI of each switch with the show smartfabric cluster command. If PREFERRED-MASTER
is true
, the preferred leader flag is set on that switch.
Leaf1A# show smartfabric cluster
----------------------------------------------------------
CLUSTER DOMAIN ID : 100
VIP : fde2:53ba:e9a0:cccc:0:5eff:fe00:1100
ROLE : MASTER
SERVICE-TAG : JVSZZP2
MASTER-IPV4 : 100.67.76.12
PREFERRED-MASTER : true
----------------------------------------------------------
Check preferred leader status on new switches
Run the show smartfabric cluster command on each 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 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 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 the show smartfabric cluster command again on each affected switch to confirm PREFERRED-MASTER
is no longer set to true
.