Enabling the DHCPv6 Server Function

Context

When the device functions as a DHCPv6 server, the DHCPv6 server function can be enabled in the system view or interface view.

Enable the DHCPv6 server function in the interface view.

Enable the DHCPv6 server function and specify the IPv6 address pool on the interface that connects the device to the DHCPv6 clients. After receiving the DHCPv6 request packets sent by the clients from the interface, the device assigns configuration parameters such as IPv6 addresses or DNS server addresses to the DHCPv6 clients from the IPv6 address pool bound to the interface.
- If the DHCPv6 server and DHCPv6 clients are in the same link scope (that is, no DHCPv6 relay exists), configuration parameters such as IPv6 addresses or DNS server addresses are assigned to the DHCPv6 clients on the interface of the DHCPv6 server.
- If the DHCPv6 server and DHCPv6 clients are in different link scopes (that is, a DHCPv6 relay exists), configuration parameters such as IPv6 addresses or DNS server addresses are assigned to the DHCPv6 clients in one network segment connected to the DHCPv6 relay.
- Only one IPv6 address pool can be specified on an interface.
- If the DHCPv6 server function is enabled in the interface view, the configuration information only takes effect on the interface.
Enable the DHCPv6 server function in the system view.

The DHCPv6 server and DHCPv6 clients are in different link scopes (that is, the DHCPv6 relay exists). If the DHCPv6 server function is enabled in the interface view, configuration parameters such as IPv6 addresses are assigned only to the clients in one network segment connected to the DHCPv6 relay, because only one IPv6 address pool can be specified on an interface. If configuration parameters such as IPv6 addresses need to be assigned to the DHCPv6 clients in multiple network segments through the DHCPv6 relay, enable the DHCPv6 server function in the system view.

The configuration method of enabling the DHCPv6 server function in the interface view is affected by the physical interface status. If the interface status is Down, the DHCPv6 server cannot successfully assign network configuration parameters to clients through the DHCPv6 relay. When the DHCPv6 server function is enabled in the system view and there are multiple reachable routes between the DHCPv6 relay and DHCPv6 server, configuration parameters such as IPv6 addresses can be assigned to clients through the DHCPv6 relay as long as one route between the DHCPv6 relay and DHCPv6 server is reachable. This improves reliability of the configuration information obtained by the clients. In addition, no configuration is required on the interface, which reduces the administrator's maintenance workload.
- If the DHCPv6 server function is enabled in the system view, the configuration information takes effect on all interfaces of the device.
- If the DHCPv6 server function is enabled concurrently in the system view and interface view, the configuration in the interface view takes precedence over that in the system view.

Procedure

Enable the DHCPv6 server function in the interface view.
1. Run system-view
  The system view is displayed.
2. Run dhcp enable
  The DHCP service is enabled.
3. Run ipv6
  The IPv6 function is enabled globally.
4. Run interface interface-type interface-number
  The interface view is displayed.
5. (Optional) On an Ethernet interface, run undo portswitch
  The interface is switched to Layer 3 mode.
  
  By default, an Ethernet interface works in Layer 2 mode.
  
  Only the S5720-EI, S5720-HI, S5730-HI, S5731-H, S5731-S, S5731S-H, S5731S-S, S5732-H, S6720-EI, S6720-HI, S6720S-EI, S6730-H, S6730S-H, S6730-S, and S6730S-S support switching between Layer 2 and Layer 3 modes.
6. Run ipv6 enable
  The IPv6 service is enabled on the interface.
7. Run ipv6 address { ipv6-address prefix-length |ipv6-address/prefix-length }
  The global unicast IPv6 address is configured for the interface.
8. Run dhcpv6 server pool-name [ allow-hint | preference preference-value | rapid-commit | unicast ] ^*
  The DHCPv6 server function is enabled on the interface.
  
  By default, the DHCPv6 server function is disabled in the interface view.
Enable the DHCPv6 server function in the system view.
1. Run system-view
  The system view is displayed.
2. Run dhcp enable
  The DHCP service is enabled.
3. Run ipv6
  The IPv6 function is enabled globally.
4. (Optional) Run dhcpv6 server { allow-hint | preference preference-value | rapid-commit | unicast } ^*
  The behavior of the DHCPv6 server is configured.
  
  By default, no behavior is configured for the DHCPv6 server in the system view.
When functioning as a DHCPv6 server, the device may be configured with multiple IPv6 address pools. After receiving the DHCPv6 request packets, the DHCPv6 server chooses the IPv6 address pool based on the following rules:
- If a relay exists, the server chooses the address pool that belongs to the same link scope with the configured network prefix (using the link-address command) or IPv6 address prefix (using the address prefix command) based on the first link-address field that is not 0. The link-address field identifies the link scope of the DHCPv6 clients.
- If no relay exists, the DHCPv6 PD server function cannot be enabled in the system view.

Follow-up Procedure

For clients (such as PCs) that automatically obtain IPv6 addresses based on IPv6 RA packets by default, flags in RA messages need to be configured on the client gateways so that the clients can obtain IPv6 addresses using DHCPv6.

When the DHCPv6 relay does not exist and the device function as the client gateway:
1. Run system-view
  
  The system view is displayed.
2. Run interface interface-type interface-number
  
  The interface view is displayed.
3. Run undo ipv6 nd ra halt
  
  The RA packet sending function is enabled on the device.
  
  By default, the switch for sending the RA packets is disabled.
4. Run ipv6 nd autoconfig managed-address-flag
  
  The managed address configuration flag (M flag) of stateful auto-configuration in an RA packet is configured.
  
  By default, the M flag in the RA packet is not configured.
5. Run ipv6 nd autoconfig other-flag
  
  The other flag (O flag) of stateful auto-configuration in an RA packet is configured.
  
  By default, the O flag in the RA packet is not configured.
  
  After the M flag and O flag of stateful autoconfiguration in the RA packet are configured, the client can obtain an IPv6 address using DHCPv6.
When the DHCPv6 relay exists and functions as the client gateway, the configuration needs to be performed on the DHCPv6 relay device. Perform configuration based on the preceding steps.