I know a nearby WISP that gives his customers IP space and his CPE space on the same last 3 octets. Makes figuring out who's CPE belongs to who's equipmnent much easier:

For example: Customer addr =, CPE addr:

We keep out CPE private, and customer addr public, but we aren't quite THAT organized.


Ryan Langseth wrote:


On Thu, 2006-11-09 at 11:23 -0600, David E. Smith wrote:
As part of the ongoing (does it ever stop?) efforts to make a Better
Network, I've finally started using private subnets where appropriate.

I'd love to be able to better automate some parts of my network, though,
and I'm not sure how to do both of 'em at the same time. (Right now,
substantially our whole network uses static IP assignments everywhere,
and that's not really viable long-term.)

My ideal scenario would be something like this:

* The AP runs a DHCP server and talks to a RADIUS server (that's easy)
* When a client associates, do a RADIUS lookup to see if they should be
 allowed to associate (that's easy too)
* Give the CPE an IP address from one subnet, then give "whatever else
 is there" an IP from a different subnet (that's the tricky part)
Why not have the AP run a DHCP relay instead of a full server, have
everything relayed to a central server of your choice that way IP
management becomes a one stop shop. Reservations would take care of
setting IPs for specific mac addresses.
This is made even more complicated by the fact that many of our CPE are
Senao CB3 units, which do MAC cloning and I don't think you can turn it
off. (Basically, both the CPE and the customer's router, or whatever,
show up in my tower as having the CPE's MAC.)
We are currently setting two IPs for each customer using a cb3, one for
the cb3 and one for the customer's equipment ( router, computer etc ) so
you should be able to apply a different IP for each piece of equipment.

If I weren't trying to conserve public IP space, this would be easy
enough - just give the CPE one IP address and the customer's gear a
second one. But there's really no reason for my radios to be visible to
the public Internet, and it's wasteful of those sweet sweet IPs.

I know there's a solution to this problem, because that's basically how
most cable modem setups work. (Annoyingly, I can't get my company's
wireless Internet at home, so I've got cable modem there.) The cable
modem is a bit "smarter" than a CB3, though, thanks to DOCSIS. I'd like
to do all this at the tower, instead of having to buy (or invent) new
CPE if possible.

Is this even possible?
Anything is possible.

I am planning a similar system, hopefully deployed by the first of the
year. Along with our own IPs from ARIN and all new bandwidth.

David Smith

Ryan Langseth

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