Where to buy Internet IP addresses

Jack Bates jbates at brightok.net
Tue May 5 14:49:01 CDT 2009


Mikael Abrahamsson wrote:
> Why wouldn't DHCPv6-PD work within the home as well as between the ISP 
> and the home?
> 
DHCPv6-PD requires manual configuration.

> I see little reason why the main home gateway can't get a /56 from the 
> ISP, and then hand out /62 (or whatever) to any routers within the home 
> that asks for PD?
> 

Sure, but how does the router know it needs to hand out a /62? Then what 
about the router after that? Does it hand out a /61? then the router 
behind that?

What if the ISP only gave a /60?

The problem with automatic arbitrary splitting of a prefix into smaller 
prefixes is that the entire topology is unknown. In such a case, 
bidirectional communication is useful, as is multiple prefix assignments 
to a single node generated from chaining DHCPv6-PD requests.

PD is not designed for multiple stage delegations without manual 
configuration for each stage.

Even the PD clients I tried on linux failed horribly in how they 
assigned a prefix to the interfaces. One of them just took the prefix 
length and divided it by the number of interfaces. Another, which I 
ended up using allowed you to set the bits to use as a subnet, but that 
meant you had to know the length from the ISP, and then the desired 
length on each of the interfaces to set the appropriate SLA (ie, I 
couldn't tell it I want a /64 on the interface, but instead had to tell 
it the SLA is 4 bits, which from a /60 would give a /64, but if I 
received a /56 it would break and have to be changed to 8 bits).


-Jack




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