To replace a Control Certificate on an appliance
Control->Access Control->Select Engine->Select Details->Click Manage
The following window appears.
Most often, the radius certificate is the one that expires, and is often replaced by a well known third party certificate starting with the CSR process.
This article assumes the newly generated certificate is generated and is in the correct format.
Click on the certificate you wish to replace
Select the certificate. It is most likely you will need to add the .key file (with password) and the certificate itself.
So you will likely need to add the use password format unless a PKS12 certificate (has both key and cert) is installed, if so, select that checkbox.
If you wish to just use the default Extreme Certificate, select Generate Certificate. Keep in mind, this is not a well know certificate to operating systems.
If the validate certificate is used on the operating system, the authentication will likely fail. However, if it was used in the past and expired, you can use the generate certificate to replace the local certificate with an updated one.
Confirm the new certificate.
Click Yes to add
You should see an operation completed successfully pop up window if it successfully imported. Click OK
Then you must enforce the appliance for this to take affect.
Select the engine again, right click, select enforce.
Select Appliances to Enforce and then Click Enforce, or Enforce all to enforce all appliance changes.