Subject: NetBSD vs. PPPoA (with native IPv6)
To: None <>
From: Matthias Scheler <>
List: regional-london
Date: 05/03/2006 15:29:18

like most NetBSD users I've talked to I've used an ADSL router in the
past to connect my NetBSD boxes to a BT ADSL service (in my case via
AAISP). Such a setup has various disadvantages:

1.) If you have only 1 public IPv4 address it will be used by the router
    and you can provide service only via NAT.

2.) Even if you have multiple public IPv4 addresses you either have to
    use a briding firewall (difficult), a transfer network (not possible
    with most providers) or settle for the poor firewall functionality
    offered by the ADSL router.

3.) It cannot support native IPv6 over the ADSL line unless the router
    supports it, too. It seems that the Cisco 872 is the only ADSL router
    on the market which supports IPv6. And like all Cisco products it is
    expensive (and has probably a lot of bugs in its IOS ;-).

The only alternative solution I've heard about is to use a SpeedTouch
330 USB ADSL Modem. These modems are only supported via driver for the
the NetBSD port FreeBSD's Userland PPP. Besides causing considerable
overhead (because network traffic is copied between kernel and
userland several times) this solution supports neither native IPv6
(unless somebody ports a newer version of the Userland PPP) nor ADSL 2+.

Searching for a better solution I found the Linksys ADSL2MUE. Besides
being a very simple ADSL router it can also act in "Bridge Mode".
While running in this mode it will look out for PPPoE (PPP over
Ethernet) packets on its ethernet interface and send them out as
PPPoA (PPP over ATM) packets over its ADSL interface and vice versa.
And PPP over Ethernet is supported by NetBSD very well via the
pppoe(4) network interface. This allows you to use a NetBSD box as
the ADSL router quite easily and without burning a lot of CPU time.

I'm using such a setup at home since a few days with a SPARCstation 20
acting as firewall and ADSL router. It is connected to the ADSL2MUE
modem over an extra ethernet interface (probably not necessary). On
that interface it uses IPv4 for configuring and monitoring the modem
and PPPoE for the DSL connection. This setup works reliable and fast
(getting the ADSL router out of the IP routing improved ping times by
a few milliseconds) and allows me to use AAISP's support for native
IPv6 over DSL connections (without any tunneling).

I hope somebody else finds this suggestion useful, too.

	Kind regards

Matthias Scheler