In order to avoid difficulties after updating to firmware version 4.50, the second registrar address must not be the IP that is already registered as registrar.
Background: It was noticed that in one installation the same server was registered as primary registrar and also as second registrar.
As a result, conversations broke off after an indefinite period of time. The time was between 30 and 50 seconds.
In this configuration field, only the standby server may be entered as the second registrar, if one exists, otherwise the field must be left blank.