You may need to edit trusted internal as well as external IP addresses.
To edit a trusted internal or external IP address
In Symantec Endpoint Protection Manager, click Admin.
Select and expand the group of Enforcers.
Select the group of Enforcers for which you want to edit a trusted internal or external IP address.
Under Tasks, click Edit Group Properties.
In the Gateway Settings dialog box, on the Auth Range tab, in the Trusted IP address range area, select Trusted Internal IP address range or Trusted External IP address range from the drop-down list.
The addresses for the selected type appear in the table.
In the Trusted IP address range table, click anywhere in the column of IP addresses and click Edit all.
In the IP Address Editor dialog box, locate any addresses you want to change and edit them.
In the Settings dialog box, click OK.