DHCPv6-4.1.mumble

Ted Lemon Ted.Lemon at nominum.com
Thu Jun 12 22:28:06 UTC 2008


On Jun 12, 2008, at 2:54 PM, Sten Carlsen wrote:
> As I see it we don't have the solution at this moment, dhcpd will give
> out EITHER IPv4 info OR IPv6 info. So you need to switch the whole
> network at one time or at least have each PC select will it be 100%  
> IPv4
> or IPv6.

No offense, Sten, but this is just silly.   dhcpd will give out IPv4  
information if you get an IPv4 address.   It will give out IPv6  
information if you get an IPv6 address.   If you get both, you have to  
choose which to use, but assuming the network is managed competently,  
that's a non-issue - it doesn't matter whether you do DNS over IPv4 or  
IPv6, for example, and DHCPv6 doesn't really configure very many more  
things than that.

We (the DHC working group in the IETF) left the decision of how to  
choose parameters up to the implementor because we didn't feel  
qualified to firmly state a single mechanism for making this choice,  
but there are a few fairly obvious mechanisms, none of which are  
particularly hard to implement:

  * use what the DHCPv4 server sends you if you get an IP address from  
DHCPv4, always.
    This is your safest bet right now.
  * Use what the DHCPv6 server sends you if you get a response from a  
DHCPv6 server, always.   Use what you get from the DHCPv4 server if  
the DHCPv6 server didn't provide equivalent information.
    This probably fairly safe even now, because DHCPv6 really only  
configures services that are known to work for IPv6.   And if your  
customer base is running dual-stack, and some parameter doesn't work  
when provided by DHCPv6, report the bug and stop providing the  
parameter until the bug has been fixed.
  * Use only what the DHCPv6 server provides, if you get a response  
from it, even if you get additional parameters from the DHCPv4 server.
    I wouldn't recommend this right now, but it's a good conformance  
testing regime if you're doing research.

If you add support for configuring IPv6 services in DHCPv4, how much  
bigger does the above list get?   IMHO, it gets a lot bigger, and  
that's a bad thing.



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