Upgrade MCT Clusters from the SLX-OS 20.1.1 Controlled Release

This procedure is based on the presence of Layer 2 VPN configuration. If Layer 2 VPN configuration is not present, swap steps 5 and 6 with steps 7 and 8 to minimize traffic loss.

Isolate Node A from the network.
1. On Node A, disable the MCT client interfaces and ICL interface.
```
device(config-cluster-1)# shutdown all
```
2. Disable the uplink to the core network.
  This command causes all CCEP traffic to switch to Node B within 10 seconds, depending on the scale and other parameters.
On Node A, copy the running configuration to the startup configuration.
```
device# copy running-config startup-config
```
Upgrade Node A to the 20.1.1 or later image using the firmware download command with the fullinstall option.
During the upgrade on Node A, traffic passes through Node B.
Verify that Node A is back online after the upgrade and initialization is complete.
Isolate Node B from the network.

Important
There is complete traffic loss at this step.
1. On Node B, disable the MCT client interfaces and ICL interface.
```
device(config-cluster-1)# shutdown all
```
2. Disable the uplink to the core network.
On Node B, copy the running configuration to the startup configuration.
```
device# copy running-config startup-config
```
On Node A, enable the uplink to the core network.
Restore Node A to the network.
```
device(config-cluster-1)# no shutdown all 
 
```
This command causes all CCEP traffic to switch to Node A within 10 seconds, depending on the scale and other parameters.
Upgrade Node B to the 20.1.1 or later image using the firmware download command with the fullinstall option.
During the upgrade on Node B, traffic passes through Node A.
Verify that Node B is back online after the upgrade and initialization is complete.
On Node B, enable the uplink to the core network.

Restore Node B to the network.

device(config-cluster-1)# no shutdown all

Save the configuration changes to the respective nodes.