[CDBUG-talk] PPPoA ... ?

Jonathan Franks jonathan.franks at gmail.com
Tue Nov 8 12:51:57 EST 2005

On 11/8/05, Patrick Muldoon <doon at inoc.net> wrote:
> On Nov 8, 2005, at 11:12 AM, Jonathan Franks wrote:
> If you are using PPPoA, then I think you need an ATM interface to
> terminate the traffic on. All of our DSL runs PPPoE or Route
> Bridged 1483, so I don't have much experience with PPPoA. But you
> can try it :) Since perhaps the DSL modem will just bridge the PPP -
> > ethernet interface and then the PPP stuff will work.
> So if I read your Above desc.
> You have ISP -> PPPoA -> DSL Modem (NAPT) -> RFC1918 Space -> OBSD
> FW -> NAT? -> clients?
> So you effectively have double NAT.

Actually it's even worse than that :-)

The modem does NAT, the OBSD FW does NAT, and the Linksys WRT54G does NAT.

ISP-> (external address) [Modem] <> -><>[PF] <> -> <>[Linksys] <> -> LAN


I suppose it's easy to see why I'd want to change this :-)

When I set it up it just never occured to me that I could just use the
WRT54G as an access point, so that's how it ended up in the chain. That part
is relatively easy to reconfigure, I just figured I'd do it all at once.
Every time I shut down the Linksys router I have to spend 20 minutes getting
the other access point, which is configured as a repeater, to see the thing
again and start, well, repeating. Needless to say I probably wouldn't use a
Linksys solution like this again... but it's there.

Incidentally, does anyone know if OBSD access points can be set up as
repeaters in this fashion? (ie: simply repeat a wireless signal with no
wired network connection) just curious.

> > The modem also offers a "half-bridge" mode which theoretically
> > authenticates to the ISP and then passes the IP back to the router.
> > Assuming that special HW is required, could this be used instead?
> Sounds like the above is what you will probably want to do, as it
> sounds like it will be the easiest to configure. The Modems that some
> of our ISP's use support ZIPB (Zero Installation PPP Bridge) which
> does the same, terminates the PPP connection and passes it on. It is
> a piece of cake to configure the firewall side, just tell it to gets
> is IP via DHCP and tell your firewall that the interface is dynamic
> and you should be good to go.
> -Patrick

Thank you, sir. Just to make certain that I understand, I would set the
external interface of my OBSD FW to use DHCP, set the modem to "half-bridge"
and essentially be all set?

I'm interested to try using pppoe just to find out if it would work, but I
think that the above does indeed sound like the way to go....
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