DHCPv6-4.1.mumble

[Simon Hobson]

bmanning at vacation.karoshi.com wrote:
>i did mention merging as an issue -IF- it was not possible to
>pass DNS server information.  to borrow from the DNS side of the
>house, it is perfectly reasonable to return, over IPv4 transport,
>data about IPv6.
>the dhcp "Domain Nameserver" option should be able to return a series
>of IP addresses that a client might use.  this capability is seriously
>crippled by the presumption that the IPv4 version of DHCP can -ONLY-
>return IPv4 addresses for this option and the IPv6 version of DHCP can
>-ONLY- return IPv6 addresses for its functional equivalent of the
>Domain Nameserver option.  The presumption seems false.
>
>If, as asserted elsewhere in this thread, the IP address string to be
>returned is unspecified then it should be fairly easy to assert that
>any valid IP address string/structure should be valid. I am working on
>patching the ISC code to do just this.

You seem to have missed the point - completely !

The existing option was defined well before IPv6 was even being 
considered, and so it was defined in terms of IP addresses taking 4 
bytes<period>. There is no 'flag' in there to say what the contents 
are, it's just a sequence of one or more 4 byte values.

Certainly, if DHCP was being started from scratch now then we almost 
certainly wouldn't come up with what we have now - but we are where 
we are.

Changing the source won't help you. You could stick an IPv6 address 
in the option, but unmodified clients will assume that it's four IPv4 
addresses and (wrongly) configure four IPv4 nameserver entries. The 
only way to fix that will be to modify EVERY client on your entire 
network - including the closed binary clients included in Windows, 
Mac OS etc. You CANNOT put a flag in there to say "this is an IPv6 
address" because that will break compatibility with unmodified 
clients.

It took years for the 'old' DHCP to be implemented and supported, 
your chances of getting all the vendors to modify existing clients in 
a timely manner is (being optimistic) approximately nil !