IPv6 Address Management
Address Pool
The BRAS uses address pools to manage addresses, such as allocating, renewing, and reclaiming addresses. The BRAS provides gateway information for access users. Address pools are classified into the following types:
Local address pool
The BRAS manages local address pools on its own. The BRAS is in charge of allocating, renewing, and reclaiming IP addresses in local address pools. A local address pool is used when the BRAS allocates a shared IPv6 prefix in ND mode or allocates an IPv6 prefix in DHCPv6 IA_PD mode.
Delegation address pool
A delegation address pool is used when the BRAS allocates an unshared IPv6 prefix in ND mode or allocates an IPv6 prefix in DHCPv6 IA_PD mode. The global unicast addresses for ND users are generated based on prefixes and interface IDs.
Remote address pool
A remote address pool is used when an external DHCPv6 server is used.
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Table 4-1 Mapping between address pools and address allocation
CPE Working Mode
IPv6 Address Allocation Mode to WAN interfaces
IPv6 Address Allocation Mode to LAN interfaces
Address Pool Type to WAN interfaces Address Pool Type to LAN interfaces Numbered routing mode
ND(shared mode) DHCPv6-PD Local Delegation Numbered routing mode
ND(unshared mode) DHCPv6-PD Delegation Delegation Numbered routing mode
DHCPv6 (local address pool) DHCPv6-PD Local Delegation Numbered routing mode
DHCPv6(remote address pool) DHCPv6-PD Remote Remote Unnumbered routing mode
NA DHCPv6-PD NA Delegation Bridging mode
ND(shared mode) NA Local NA Bridging mode
ND(unshared mode) NA Delegation NA Bridging mode
DHCPv6(local address pool) NA Local NA Bridging mode
DHCPv6(remote address pool) NA Remote NA Bridging mode
ND(remote address pool) NA Remote NA
Address Protection
When one or more addresses in an IPv6 address pool become unavailable, you can take any of the following methods:
Locking the IPv6 address pool
After an IPv6 address pool is locked, no address in this pool can be allocated. This method applies to scenarios where the IPv6 address pool fails to be deleted because it is in use. Locking the IPv6 address pool prevents the address pool from allocating addresses to new users. After all users of the address pool go offline, addresses in the IPv6 address pool will be released. You can then delete the IPv6 address pool.
Excluding specific IPv6 addresses
In complicated networking scenarios, you can use this method to prevent some IP addresses from being allocated.
Setting conflict flags
If some IP addresses in the IPv6 address pool conflict with device IP addresses, use this method to attach conflict flags to the IP addresses in the address pool. After the conflicts disappear, delete the conflict flags.
Address withdrawal
If you want to withdraw the addresses of some offline users, use this method.
Address Lease
The leases of user addresses are under management. When the lease of a user's address is close to expiration, the protocol automatically renews the address lease. The renewal will be successful so long as the requested IP address is available.
Address Reservation
- MAC reservation: The IPv6 addresses are dynamically allocated through DHCPV6 based on MAC addresses. If a user's MAC address and the allocated IP address are recorded during the first login, the user can still use the originally allocated IP address when he goes online for the second time.
MAC- and lease-based reservation: An address is dynamically allocated to a client. After the client goes offline, the binding relationship between this address and the client retains for a lease. The address is released only after the lease expires. During this lease, the address is exclusive to the client.
DUID reservation
DUID- and lease-based reservation
Address Overlapping
The IP addresses of address pools in different VPN instances can overlap each other.
