Re: IPv6 comes in the game

["Paul D. Robertson" <paul () compuwar net>]

On Tue, 4 May 2004, Lorand Jakab wrote:

> Now the box has an IPv6 address as well, and a prefix for the internal
> network, and I would like to forward IPv6 traffic too. But the above
> approach is not feasable anymore (not a good idea to have a 2^64 entry
> static neighbor cache). Is it possible to prevent using unassigned IP
> addresses to be used for Internet access without entering each assigned
> address in the firewall, while still having static MAC entries for
> registered addresses?

Surely you're not going to have 2^64 active neighbors?  I don't see how a
v6 address changes things really?

In any case, you might want to look at your layer 2 networking gear and
see if authenticating the device via 802.1x is reasonable (it's built into
the green switches, not sure about the others.)  You may be able to do
some "hand out an address by authentication group" sort of thing.  I'm not
sure what RADIUS servers support 802.1x though- and it's probably not a
well-trodden path.

> What would you recommend for this scenario, so it would only be possible
> to spoof an address, if a user changed the MAC addres of his NIC to
> another legitimate user's MAC, the IP to the other user's IP (if no
> autoconfiguration will be used, I haven't decided that yet) and the
> legitimate station would not be turned on?

If you force the user to authenticate prior to forwarding packets, as
802.1x does on switches, then you're able to log the authentication at the
RADIUS server, and equate network activity to a port.  If the port's locked
to an IP address, then you have the ability to track and basically
eliminate abuse by authenticator.

I'd probably look at RADIUS servers to see if there's any group addressing
support, so that you could enable a user's addressing request by userid to
be v4 or v6.

I really wish I had the time to fool around with 802.1x, it really looks
like the best place to do authentication, especially if you can translate
the results into VLANs or address blocks.

Paul
-----------------------------------------------------------------------------
Paul D. Robertson      "My statements in this message are personal opinions
paul () compuwar net       which may have no basis whatsoever in fact."
probertson () trusecure com Director of Risk Assessment TruSecure Corporation
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