pTLAs missing in action

[Richard Draves]

> It would be very nice if, for every piece of topology identified by an
> address prefix, the border routers of that piece of topology would
> automatically assign to themselves an anycast address consisting of
> the relevant prefix followed by all zeros.  The anycast address would
> be assigned to the interface(s) attached to the prefixed topology.
> This would allow you to ping a prefix and get an answer from 
> the nearest
> border router of that prefix.  This particular use of anycast 
> addressing
> does not impose any additional load on routing outside the piece of
> topology (since it aggregates with all the other addresses for that
> piece of topology), and adds only one entry to the routing inside the
> piece of topology (for the zero-valued next-level-down prefix).

Well this would certainly make my life easier right now.

> Note that we already require this for the border routers of subnets
> (effectively, all routers), and I recall that the IPv6 
> address allocation
> policies that the regional registries are proposing/using 
> requires this
> for border routers of sites.  I suggest we require it for the border
> routers of all prefixes.

Does anyone actually implement the subnet anycast addresses? I know I've
been lax about it, and from the brief experiment I just tried it seems Cisco
& Telebit routers also do not.

Something for UNH to check...

Rich