Array (  => Array ( [version] => 7.1 [language] => en )  => Array ( [version] => 7.0 [language] => en )  => Array ( [version] => 6.5 [language] => en )  => Array ( [version] => 6.4 [language] => en ) ) Rel: bcc/dhcp/key_concepts/bcc/dhcp/dita/provisioning_with_dhcpv6 URI: bcc/dhcp/key_concepts/provisioning_with_dhcpv6 === Tags === Array (  => provisioning with DHCPv6  => provisioning with DHCPv6 provisioning cable modems in DHCPv6  => DHCPv6 address allocation  => DHCPv6 address allocation DHCPv6 subnet rules  => DHCPv6 address allocation DHCPv6 prefix delegation rules ) === Related === Array (  => Array ( [id] => 321 [title] => DHCPv6 Prefix Delegation Rules [slug] => dhcpv6_prefix_delegation_rules [product] => bcc [component] => dhcp [category] => topics [version] => 6.4 [common_tag_count] => 1 [uri] => bcc/dhcp/topics/dhcpv6_prefix_delegation_rules )  => Array ( [id] => 326 [title] => DHCPv6 Subnet Rules [slug] => dhcpv6_subnet_rules [product] => bcc [component] => dhcp [category] => topics [version] => 6.4 [common_tag_count] => 1 [uri] => bcc/dhcp/topics/dhcpv6_subnet_rules )  => Array ( [id] => 665 [title] => Provisioning Cable Modems in DHCPv6 [slug] => provisioning_cms_dhcpv6 [product] => bcc [component] => [category] => tutorials [version] => 6.4 [common_tag_count] => 1 [uri] => bcc/tutorials/provisioning_cms_dhcpv6 ) )
Provisioning with DHCPv6
The service supports the DHCPv6 protocol as defined in RFC 3315 and related specifications. The service includes temporary and non-temporary allocations, prefix-delegation allocations, and a full range of options.
The concepts of address leasing and renewal are referred to in DHCPv6 as assigning valid and preferred lifetimes for addresses. Devices may request and be granted multiple addresses. The protocol also allows for devices to request a range of address space, which is provided by a response to prefix delegation requests.
- Non-temporary (IA_NA). These contain IPv6 addresses that are expected to be used as long as the client requests renewal.
- Temporary (IA_TA). These contain IPv6 addresses that are not expected to be renewed.
- Prefix delegations (IA_PD). These define a set of IPv6 prefixes to be allocated from a delegating router to a requesting router for prefix delegation. Prefix delegations are expected to be renewed.
A device can make requests using one or more identity association types. Each request may be for one or more IA instances and each instance may request one or more addresses or prefixes. Lease durations are specified on a per-IA basis.
DHCPv6 Address Allocation
To request allocations, clients send a SOLICIT message to the standard multicast address ‘All_DHCP_Relay_Agents_and_Servers’ (or Unicast if set in options). However, most communication from client to server occurs through a relay, which forwards the message to the server in a RELAYFORWARD message with the client message as its content.
When a client sends a SOLICIT message, it may receive multiple ADVERTISE messages in response, and it may choose to follow with a REQUEST message to one or more. If the server accepts the client request, then it will commit the allocation and respond to the client with a REPLY message.
Prefix delegation allocation handling follows a similar flow. It is distinguished by the options present in the message denoting the request for a delegation of address space. Also, some message types in the described list do not apply to prefix delegation messages, for example, CONFIRM and DECLINE messages.
The service evaluates the request information it receives from the client against the defined DHCPv6 subnet rules and prefix delegation rules. Clients can be restricted to allocation from a particular rule through client class criteria.
|SOLICIT||DISCOVER||Client sends to locate DHCP servers|
|ADVERTISE||OFFER||Server sends in response to clients sending SOLICT messages|
|REQUEST||REQUEST||Client sends to specific server determined from ADVERTISE messages received|
|CONFIRM||REQUEST||Client sends to check configuration|
|RENEW||REQUEST||Client sends to specific server to renew lease|
|REBIND||REQUEST||Client sends if RENEW is not answered|
|REPLY||ACK/NAK||Server sends in response to SOLICIT, REQUEST, etc. messages|
|RELEASE||RELEASE||Client sends to inform address can be freed on server; client no longer using it|
|DECLINE||DECLINE||Client sends to inform that address is being refused|
|RECONFIGURE||N/A||Server sends to inform willing clients that new configuration information is available|
|INFORMREQUEST||INFORM||Client sends to request option information (except lease changes)|
|RELAYFORWARD||N/A||Client sends (or any DHCPv6 relay agent), any of client side messages contained within it|
|RELAYREPLY||N/A||Server sends in response to the RELAYFORWARD, back to relay agent|