DHCPv6 and Manual Bindings

Unanswered Question
Sep 17th, 2010

With DHCPv6, do manual address bindings not apply?  I see manual bindings for prefix delegation but none for addresses.

In dhcpv4, there was the ability to specify a client-id (or hardware-address) and then use the command 'host a.b.c.d' to assign a specific address to a specific host.

In studying dhcpv6, I do not see a similar capability.

Thanks

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keiththomas Tue, 11/09/2010 - 07:16

Wow, all those Cisco folks and CCIEs out there and nobody knows! I have either stumped or bored the world's experts.

Does anyone know the answer to my question?

@jsidwell@ Tue, 11/09/2010 - 13:54

Hope this helps. 

http://www.cisco.com/en/US/tech/tk872/technologies_white_paper09186a00801e199d.shtml#wp41640

http://www.cisco.com/en/US/docs/ios/ipv6/configuration/guide/ip6-dhcp.html

If I understand your question, you are asking if you can do a one-to-one mapping between a client and an IPv6 address.  Are you looking for this mapping to be a global, link local or unique local?  What is the driver behind this requirement?  If you have the DHCPv6 configured to hand out a /64 prefix then using the manipulation on the MAC address, you will know (predictably) what the address will be:  .

Here is what Cisco has to say about their implementation of DHCPv6 (from the first link):

The Cisco IOS Software DHCPv6 function runs in routers. It is based on RFC3315 DHCPv6 specification. Prefix Delegation [PD] and DNS [DNS] DHCPv6 options are supported and allow distribution of a prefix, as well as a list of DNS servers and domain names.

The Cisco IOS Software DHCPv6 client and server are specifically intended as a PD solution and do not implement the entire DHCPv6 protocol. Cisco IOS Software DHCPv6 currently implements PD, the rapid-commit mechanism, stateless DHCPv6 ("DHCPv6-lite"), and the following:

Client Identifier option

Server Identifier option

Option Request option

Preference option

Status Code Option

Rapid Commit option

Identity Association for Prefix Delegation option (IA_PD option)

IA_PD Prefix option

Domain Name Server option

Domain Search List option

keiththomas Wed, 11/10/2010 - 13:27

Thank you , that is helpful. The server is handing out IA_NA and chooses the 'host' bits (those beyond the address prefix specified in the dhcpv6 pool.)

I was looking to see if I can also control the lower 64 bits being handed out.

@jsidwell@ Wed, 11/10/2010 - 13:58

I am not aware of a DHCPv6 server that does this.  I believe that the expectation and design for IPv6 is that the host is responsible for this (per RFC 4862).

   This document specifies the steps a host takes in deciding how to
   autoconfigure its interfaces in IP version 6.  The autoconfiguration
   process includes generating a link-local address, generating global
   addresses via stateless address autoconfiguration, and the Duplicate
   Address Detection procedure to verify the uniqueness of the addresses
   on a link.

I hope that helps.  To be clear, I am speaking of link-local addresses.  Global addresses are a different matter when mapped to a DNS name.  I would expect that any FQDN name would resolve to a static IPv6 address (or by some DDNS means).

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