The BRAS manages addresses through address pools, including assigning and renewing addresses, reclaiming DNS server resources, and providing a gateway address for access users.
Local address pool
The BRAS manages local address pools, including assigning, renewing, and reclaiming IP addresses in a local address pool. In ND shared prefix assignment or DHCPv6 (IA_NA) address assignment mode, IP addresses are assigned from a local address pool.
Delegation address pool
In ND unshared prefix assignment or DHCPv6 (IA_PD) address assignment mode, IP addresses are assigned from a delegation address pool. ND clients use ND to obtain prefixes. A prefix and an interface ID constitute a global unicast address.
Remote address pool
When an external DHCPv6 server is used, a remote address pool is used for address assignment.
The BRAS assigns an IPv6 address (for the WAN interface) and an IPv6 prefix (for the LAN interface) to a CPE.
When one or more addresses in an IPv6 address pool are not allowed to be assigned, the address pool can be protected. The following methods of address pool protection are available.
Locking an address pool
An address pool can be locked using the corresponding command. IP addresses in a locked address pool cannot be assigned any more. This method is usually used when an address pool cannot be deleted because an IP address in the pool is already used by an online user. In this case, lock the address pool so that no IP address can be assigned from this address pool. After all users go offline and all IP addresses in the address pool are released, delete the address pool.
Disabling IP addresses
In complex network planning, some IP addresses may need to be excluded.
Setting the IP address conflict flag
When an IP address in an address pool conflicts with a device's IP address, this IP address can be set to conflict using commands. After the conflict is cleared, the flag of the IP address can be reset manually.
Reclaiming IP addresses
When an IP address in an address pool is abnormal, that is, the IP address is in use but actually no user is using it, this IP address cannot be used any more. In this case, you can run a command to forcibly reclaim the IP address.
If a user fails to apply for an IPv6 address from an address pool for a specified number of times, the address pool is considered faulty and will be automatically isolated. The BRAS then preferentially selects addresses from another available address pool. If no other address pools are available, the BRAS continues to select the current address pool.
Address pool lease management is used to manage the validity period of user addresses. If the lease of a user's IP address expires and the user still wants to use this address, the user can apply for a lease renewal. As long as this IP address is valid, a lease for this address will be automatically renewed.
When one MAC address maps to multiple sessions, IPoE users are identified based on the MAC address, access interface, and access VLAN of the client. When a client goes online for the first time, an IP address is first dynamically assigned to the client.
A VPN instance can be configured for an address pool. The IP addresses in the address pool corresponding to a VPN instance can overlap with those in the address pool corresponding to another VPN instance.