access-user dhcp auto-save

Usage Scenario

In a DHCPv4 user access scenario in which the NetEngine 8000 F functions as a BRAS, when the NetEngine 8000 F is restarted or its board, subcard, or interface is faulty, DHCPv4 users are logged out and their information is lost. If a DHCPv4 client does not detect the fault, the DHCPv4 client does not resend a DHCP request packet to the device or redial up after the fault is rectified. As a result, the DHCPv4 user cannot go online again. To address this problem, save DHCPv4 user information automatically before any fault occurs and allow the DHCPv4 users to go online automatically after the fault is rectified.

The DHCPv4 users include those who share one MAC address but go online from multiple sessions.

To automatically save DHCPv4 user information, run the access-user dhcp auto-save command globally to enable automatic backup of DHCPv4 user information and specify the maximum number of DHCPv4 users whose information can be backed up in all domains.

Configuration Impact

The access-user dhcp auto-save command applies for a memory space based on the maximum number of DHCPv4 users. If the command cannot apply for the size of contiguous memory space, the command fails to be executed, and automatic backup of DHCPv4 user information is disabled.

You must also run the access-user dhcp auto-save enable (domain view) command in a domain to automatically back up DHCPv4 user information. The information about DHCPv4 users in a dual-system hot backup scenario is not saved.

The device backs up only information about the configured maximum number of DHCPv4 users in all domains. The excessive part of DHCPv4 user information is not backed up. Specify <max-user-num> as the total number of DHCPv4 users whose information needs to be backed up in all domains.

Follow-up Procedure

Run the access-user dhcp auto-save enable (domain view) command to enable automatic backup of DHCPv4 user information in a domain.

Run the access-user dhcp auto-recover enable command to enable automatic DHCPv4 user login.

Precautions

This command is supported only on the admin VS.

NOTE:

The following DHCPv4 user information is saved: MAC address, IP address, VLAN, access interface, VPN instance name, domain name, lease, Option 82, Option 60, Option 61, and IP address of the DHCPv4 server. The DHCPv4 user information is used only when the DHCPv4 users go online automatically.

Note:

If the memory space is insufficient, automatic backup of DHCPv4 user information may affect other services. Exercise caution when using this function.

Running the access-user dhcp auto-save command may fail if memory fragments exist. Therefore, it is recommended that you run the command when the system just starts or the traffic load is light.

The command configuration consumes memory resources that are in direct proportion to <max-user-num> . Specify <max-user-num> based on the maximum number of DHCPv4 users to be backed up to prevent high memory usage.