Re: IPv6 fc00::/7 — Unique local addresses

Jay Ford jay-ford at uiowa.edu
Wed Oct 20 21:54:43 UTC 2010


On Wed, 20 Oct 2010, Jeroen van Aart wrote:
> According to http://en.wikipedia.org/wiki/IPv6_address#Special_addresses an 
> fc00::/7 address includes a 40-bit pseudo random number:
>
> "fc00::/7 ? Unique local addresses (ULA's) are intended for local 
> communication. They are routable only within a set of cooperating sites 
> (analogous to the private address ranges 10/8, 172.16/12, and 192.168/16 of 
> IPv4).[12] The addresses include a 40-bit pseudorandom number in the routing 
> prefix intended to minimize the risk of conflicts if sites merge or packets 
> are misrouted into the Internet. Despite the restricted, local usage of these 
> addresses, their address scope is global, i.e. they are expected to be 
> globally unique."
>
> I am trying to set up a local IPv6 network and am curious why all the 
> examples I come accross do not seem to use the 40-bit pseudorandom number? 
> What should I do? Use something like fd00::1234, or incorporate something 
> like the interface's MAC address into the address? It'd make the address 
> quite unreadable though.

Use the cool tool at http://www.sixxs.net/tools/grh/ula/ to generate a ULA, 
then use it for local-scope stuff.  Slick.

________________________________________________________________________
Jay Ford, Network Engineering Group, Information Technology Services
University of Iowa, Iowa City, IA 52242
email: jay-ford at uiowa.edu, phone: 319-335-5555, fax: 319-335-2951




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