You cannot delete your previous default gateway when you reconfigure your existing ProxySG for different network segment. To delete a previous default gateway, the IP address of the previous default gateway must be the same as the NIC IP address.

In order to modify or delete previous default gateway and configure the ProxySG appliance for the current network:

1. Record the NIC IP address.
2. Change the NIC IP address to be the same as the previous default gateway IP address.
3. Modify or delete the previous default gateway.
4. Change the NIC IP address to the address you recorded in the first step.

Note:

It is also possible to remove the old gateway by previously changing an interface that you are not using. This should be a safer method as it doesn't tamper with any existing configuration. If this is the case, the steps are as follows:

1. Go to an interface you are not using (no IPv4 address configured)
2. Add the IP of your Gateway to the interface and apply the change.
3. Delete the gateway from the Routing configuration.
4. Delete the IP you added to the non-used interface (as it is no longer required).