IPv6 DHCP configuration

[Steph1963]

Hi,

I am trying to configure a IPv6 DHCP server and I found the following thread discussing two different configurations:

https://learningnetwork.cisco.com/thread/10339

Configuration 1

ipv6 dhcp pool TEST
prefix-delegation 1111:2222::/32 1234ABCD
prefix-delegation pool TEST lifetime 1800 60
dns-server 1111:2222::13
domain-name PIPROUTING.NET

Configuration 2

ipv6 dhcp pool Test-Me2
  address prefix 2000:CC1E:0:1E1E::/64 lifetime infinite infinite
  link-address 2000:CC1E:0:1E1E::AA/64

Is there anybody who knows the difference between using

prefix-delegation 1111:2222::/32 1234ABCD
prefix-delegation pool TEST lifetime 1800 60

as opposed to

  address prefix 2000:CC1E:0:1E1E::/64 lifetime infinite infinite
  link-address 2000:CC1E:0:1E1E::AA/64

What it purpose of the link-address command? Will it be used by a DHCP client to determine it`s link-local address.

Note: Any link that would explain me the prefix-delegation would be greatly appreciated

Thanks for your help

Stéphane

[Peter Paluch]

Hi Stéphane,

Just a quick answer, certainly not covering all your questions but just as a starting point: try to read the following portion of the IOS Configuration Guide about IPv6:

http://www.cisco.com/en/US/docs/ios/ipv6/configuration/guide/ip6-dhcp_ps6441_TSD_Products_Configuration_Guide_Chapter.html

It may answer some of your questions.

Best regards,

Peter

[Steph1963]

Hi Peter,

The part that I do not understand with this delegation concept is the client-duid iaid

prefix-delegation ipv6-prefix/prefix-length client-duid [iaid iaid] [lifetime]

Router(config-dhcp)# prefix-delegation 
2001:0DB8:1263::/48 0005000400F1A4D070D03

 
 What is the client-duid [iaid], where can we find it on a host PC. Is it something we can configured on a PC or is it something that is present by default.

Thanks for your help

Stephane

[Peter Paluch]

Hello Stéphane,

The DUID is the DHCP Unique  Identifier. It is a value that uniquely identifies the DHCP client and  server. On a Cisco device, you can display it using the command

show ipv6 dhcp

It is described in the document I've referenced, specifically:

http://www.cisco.com/en/US/docs/ios/ipv6/configuration/guide/ip6-dhcp_ps6441_TSD_Products_Configuration_Guide_Chapter.html#wp1055483

It is also used by DHCP clients such as PCs but because these clients do not use prefix delegation, you do not need to know the value for an ordinary PC.

Best regards,

Peter