(Optional) Configuring Global DHCPv4 Parameters

Procedure

1. Run system-view

   The system view is displayed.

2. Run dhcp slot-id max-sessions user-number

   The maximum number of DHCPv4 access users allowed for a specified board is set.

3. Run dhcp check-client-packet strict

   The function to strictly check packets from a DHCP client is enabled.

4. Run dhcp-server ip-address [ vpn-instance vpn-instance ] send-discover-speed packet-number time-value

   A limit on the packet transmission rate of a DHCPv4 server group is set.

5. Run dhcp server identifier dest-ip

   The destination IP address of a packet forwarded by a DHCP relay is set as the identifier of the DHCP server.

   After the dhcp server identifier dest-ip command is configured, the DHCP response packet forwarded by the NetEngine 8000 F carries the destination IP address of the request packet as the DHCP server identifier.

   The command only applies to a scenario in which the NetEngine 8000 F is not the first PE and functions as the DHCP server.

6. Run dhcp request-ip-address check { enable | disable }

   Check of DHCP request packets with Option 50 is disabled or enabled.

   After a user sends a DHCP request packet with option 50, the NetEngine 8000 F authenticates the user. If the requested IP address has been assigned to another user, the NetEngine 8000 F replies an NAK packet to the user. If a large number of users resend DHCP Discover packets to apply for IP addresses, the NetEngine 8000 F authenticates the users again, causing high CPU usage. To resolve this problem, run the dhcp request-ip-address check enable command to enable check of DHCP request packets Option 50. After that, if the request IP addresses have been assigned to other users, the NetEngine 8000 F replies NAK packets without authenticating users again. In this manner, high CPU usage is prevented.

7. (Optional) Run dhcp giaddr zero user-type layer2

   The device is enabled to set the giaddr field to 0 in a DHCPv4 message to be sent to a DHCPv4 client in Layer 2 access scenarios.

8. Run access-line-id attach

   The BRAS is enabled to send Option 82 information to the RADIUS server if user packets do not carry Option 82 or the BRAS does not trust Option 82 in user packets.

9. (Optional) Run dhcp rebind no-user action keep-silence

   The device is disabled from sending an NAK message in response to a client's DHCP Rebind message if no corresponding user entry exists on the device.

10. Run commit

    The configuration is committed.