Need some assistance with IPv6 addresses

[Andrew Falanga]

Hi,

At work I have a FreeBSD machine that I use for various testing and I need
to setup an IPv6 only LAN using this machine.  To this end, I have a few
questions.

1)  How can I remove an address from an interface using ifconfig (or other
utility)?  That is, I want to remove all IPv6 addresses this system might
already have (except of course the link-local address fe80) and create new
ones the fly and I don't want to reboot every single time.

2) Second, how, exactly, does the prefix length figure into things.  I am
reading up on IPv6 using various sources such as RFC's and the Handbook and
what it says about IPv6, but when I assigned an address of fec0/10
(mentioned in the handbook) I can't ping the other system I assigned the
same address to.  In the handbook, I noticed that it linked to RFC 3513 and
in that RFC it specifies the following:

Site-Local addresses have the following format:

   |   10            |
   |  bits           |         54 bits         |         64
bits            |
   +----------------+-------------------------+----------------------------+
   |1111111011|        subnet ID        |       interface ID         |
   +----------------+-------------------------+----------------------------+

Which is fec0:<subnet>:<interface>

>From the above, I'd assume that the prefix length should be /64.  But this
is assuming that my understanding of the prefix length is correct in that it
is synonimous with the subnet mask in IPv4.  This is what I originally
thought, but thought I might be incorrect when I read in the handbook that
the prefix length for fec0 is /10.  So, on my FreeBSD system I did this
(after a reboot, which I'd really rather avoid):

ifconfig sis0 inet6 fec0:1:1:1::1/10

I can ping this address but not the other system I configured like this with
fec0:1:1:1::2/10.  So, where is my error in IPv6?  Second, how do I remove
previous IP addresses from an interface with rebooting?

Andy