Persistent DUID (DHCP Unique Identifier) for Server

[Simon Hobson]

At 06:11 +0000 25/11/11, Madhu Krishna Sandadi wrote:

>>Bear in mind that the RFC _requires_ that the DUID_LL only be used 
>>in cases where the hardware address is hard-wired, and can't be 
>>changed either by changing hardware or overwriting firmware.

>I need one clarity from rfc-3315. It says  from session 9.2 for DUID-LLT
>
>Clients and servers using this type of DUID MUST store the DUID-LLT
>in stable storage, and MUST continue to use this DUID-LLT even if the
>network interface used to generate the DUID-LLT is removed. Clients
>and servers that do not have any stable storage MUST NOT use this
>type of DUID.
>
>
>It says that even if we remove the network interface that used to 
>generate the DUID-LLT.
>That means do we need to use the same DUID even if we replace the 
>new network interface card that has new link layer address.

DUID-LLT is different to DUID-LL

LLT includes a time element, LL does not.

Thus if you were using LLT and changed the hardware - moving it to 
another device - then that other device would be exceedingly unlikely 
to generate the same DUID-LLT value since it's clock would be 
different. Thus it would be same to continue using the same DUID-LLT 
value even if your hardware address changes.

With DUID-LL, if your hardware changes, then you cannot be 100% 
certain that another device won't get that hardware and generate the 
same value.

-- 
Simon Hobson

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