3Com 3C13636 Configuration Manual page 453

3Com Router 3000 Ethernet Family
Configuration Guide
Figure 9-3 Structure of the DHCP accounting packet
Code: One byte for identifying the type of the DHCP accounting packet. A value of
4 indicates an accounting start request, while a value of 5 indicates an accounting
stop request. If the Code field of an accounting packet is not valid, the packet is
discarded.
Identifier: One byte for matching requests and responses. The RADIUS server
checks this field for duplicate requests from the same IP address and UDP port of
a client.
Length: Two bytes for identifying the length of the accounting packet.
Authenticator: 16 bytes for identifying the information between the RADIUS server
and client.
II. Fundamental of DHCP accounting
After you complete AAA authentication and RADIUS configuration on a router with the
DHCP server function enabled, the DHCP server acts as a RADIUS client. For the
authentication process of the DHCP server acting as a RADIUS client, refer to the
"Introduction to the RADIUS Protocol" section of the "Security" part in this manual. The
following describes only the interactive accounting operations between the DHCP
server and the RADIUS server.
After sending a DHCP_ACK packet with the IP configuration parameters to the
DHCP client, the DHCP server sends an accounting start request to the specified
RADIUS server. The RADIUS server processes the accounting start request,
makes a record, and sends a response to the DHCP server.
Once reclaiming a lease for some reason, the DHCP server sends an accounting
stop request to the RADIUS server immediately. The RADIUS server processes
the accounting stop request, stops the recording for the DHCP client, and sends a
response to the DHCP server. A lease can be reclaimed for an expired lease, a
release request from the DHCP client, a manual reclamation operation, an
address pool removal operation, and the like.
3Com Corporation
9-6
Chapter 9 DHCP Configuration