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# Overview of IP Address Manager Integration

You use the Monitoring Agent application with the event notification method of logging in subscribers and creating subscriber sessions. You can use event notification when you integrate devices into the SRC network that do not notify the SAE about subscriber events, such as when a subscriber logs in or when the address assignment is terminated.

For example, you can use monitoring agent in a cable network. When events occur between the IP address manager and the cable modem termination system (CMTS) device or PacketCable Multimedia Specification (PCMM) device driver, Monitoring Agent creates event notifications on the IP address manager that are delivered to the SAE using the event notification application programming interface (API).

For information about event notification in the PCMM network, see SRC PE Solutions Guide.

For information about event notification with other third-party network devices, see SRC PE Getting Started Guide.

The Monitoring Agent application monitors DHCP or RADIUS messages for DHCP or RADIUS servers running on the same host as Monitoring Agent and generates subscriber events. Monitoring Agent intercepts messages on every available interface unless configured to do otherwise in the property file.

The Monitoring Agent application must run on every server host that can allocate IP addresses to subscribers. Monitoring Agent is stateless and cannot synchronize the current set of subscribers when there is a failure. If events are missed because of a software or network failure, the overall state recovers when DHCP leases are renewed or RADIUS interim updates are sent. For example, missed ipUp events become effective when the affected lease is renewed or the next interim update is sent, and missed ipDown events time out when the lease expires or after the configured RADIUS time to live.

The Monitoring Agent application can be configured as the pseudo–RADIUS server. In this case, Monitoring Agent acts as a RADIUS accounting server and no longer needs to run on the same host as the RADIUS server. However, your router or RADIUS server should be configured to duplicate accounting packets to Monitoring Agent. When Monitoring Agent is the pseudo–RADIUS server, it handles software failures more robustly. The pseudo–RADIUS server does not acknowledge failed accounting requests and gives the RADIUS client the option to retransmit the accounting packet to a backup Monitoring Agent.

## Monitoring DHCP Messages

When Monitoring Agent is intercepting DHCP messages, it captures every UDP packet that is received or sent on UDP port 67 (BOOTP/DHCP server).

Monitoring Agent processes messages for the following DHCP message types:

- DHCPACK—Sent from the server to the client when a lease is acknowledged. The Monitoring Agent application translates the client IP address and IP address lease time into an ipUp event.
- DHCPNAK—Sent from the server to the client when a lease is not renewed or the client configuration is wrong. The Monitoring Agent application translates the client IP address into an ipDown event.
- DHCPRELEASE—Sent from the client to the server when the client cancels the lease. The Monitoring Agent application translates the client IP address into an ipDown event.

All other DHCP messages are ignored.

## Monitoring RADIUS Messages

When Monitoring Agent is intercepting RADIUS accounting messages, it captures every UDP packet that is sent to the RADIUS accounting port (1813 is the default port).

Monitoring Agent processes messages for the following RADIUS attributes:

- Acct-Status-Type (RADIUS attribute [40])—Start and interim update events are translated into ipUp events. Stop events are translated into ipDown events.
- Framed-Ip-Address (RADIUS attribute [8])—The IP address identifies the notified interface.
- Acct-Session-Id (RADIUS attribute [44])—The accounting session ID is set as the EA_SESSION_ID attribute of the event notification.
- NAS-Port-Id (RADIUS attribute [87])—If present, the NAS port ID is set as the EA_NAS_PORT_ID attribute of the event notification.

The RADIUS client must send interim update accounting requests with a known frequency because the Monitoring Agent application cannot keep the state of logged subscriber sessions. To allow for lost messages, you might set the timeout value for ipUp notifications to a value that is larger than the interim update interval. For example, setting the timeout value to twice the interim update interval allows for one lost message.

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