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Figure 142 Access procedure for a DHCPv4 user
DHCP client
(1) DHCP-DISCOVER
(11) DHCP-ACK
1.
The DHCP client sends a DHCP-DISCOVER message to the BRAS.
2.
The BRAS inserts Option 82 in the DHCP-DISCOVER message, and creates an IPoE session.
3.
The BRAS sends the AAA server an access request that includes user information, such as the
client ID and source MAC address.
4.
The AAA server returns an access accept that contains authorization information to the BRAS if
the authentication succeeds. If the authentication fails, the AAA server returns a reject
message.
5.
The BRAS marks the IPoE session state as success and forwards the DHCP-DISCOVER
message to the DHCP server if the authentication succeeds. If the authentication fails, the
BRAS marks the session as failure and discards the DHCP-DISCOVER message.
6.
The DHCP server sends a DHCP-OFFER message to the BRAS.
7.
The BRAS forwards the DHCP-OFFER message to the DHCP client.
8.
The DHCP client sends a DHCP-REQUEST message to the BRAS.
9.
The BRAS forwards the DHCP-REQUEST message to the specified DHCP sever.
10. The DHCP server sends a DHCP-ACK message containing the assigned IP address to the
BRAS.
11. The BRAS performs the following:
a. Obtains address information from the DHCP-ACK message.
b. Assigns a user profile.
c. Updates the IPoE session information.
d. Forwards the DHCP-ACK message to the client.
BRAS
(DHCP relay)
(2) Inserts Option82 and
initiates an IPoE session.
(5) Updates the IPoE session
as an authorized session.
(6) DHCP-DISCOVER
(7) DHCP-OFFER
(8) DHCP-REQUEST
(9) DHCP-ACK
(10) Completes IPoE session
establishment.
387
DHCP server
(3) Access Request
(4) Access Accept
(12) Accounting-Start
AAA server
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