The SBC Core communicates with the external PSX over the Management Interface and Packet Interface. The SBC core can choose any alternate IP addresses attached to the Packet Interface to communicate with the external PSX over the Management Interface and/or Packet Interface.
The communication between the SBC and the external PSX follows a sequence, as described below:
The SBC requests registration and receives response from PSX.
The SBC periodically sends request to know the status of external PSX.
The SBC requests for policy and receives response.
The SBC requests for de-registration and receives response.
The SBC global configuration includes an optional metaVariable field (ipVar) to fetch an IP address from the PSX for use in connecting with the PSX. When the ipVar field is blank, the SBC picks any random IP address from the configured interface to connect with the PSX.
Additionally, the interfaceIpAddress field is added to the policyServer 'show' command to identify the IP address the SBC uses to communicate with the PSX for the specified Policy Server.
Refer to Use Alternate IP Address to Communicate to the PSX for details.