host-identifier with IPv6

Ted Lemon Ted.Lemon at
Mon Mar 2 03:44:33 UTC 2009

On Mar 1, 2009, at 7:52 PM, Frank Sweetser wrote:
> And what if, rather than a fixed address, the address assignment  
> were a
> dynamic one?  In DHCPv4, the client would get a different address,  
> but a
> number of people would be happy if it were legal for it to get the  
> same one
> instead.

Two things.   First of all, implementors are encouraged to provide  
ways for things like DUIDs to be known by all the protocol agents that  
might use them.   But of course we have no control over what  
implementors actually do.

Secondly, with DHCPv6, there simply isn't a shortage of IP  
addresses.   So if you set an artificial goal of absolutely never  
having a client get a different IP address in the boot prom than in  
the operating system, you may have trouble.   But if your goal is  
simply to notice that two clients are the same device, you can do that.

You can always come up with a scenario where you can show that DHCP  
doesn't do what you want in that scenario.   But each specific  
behavior of DHCP is there for a reason.   Rather than attempting to  
engineer a different protocol that does precisely what you want, and  
in the process opening yourself up to all the interoperability  
problems we were trying to avoid when we wrote the spec, why not  
simply figure out how to get what you need in the context of the spec  
as written?

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