[SWLUG] ADSL Routers.

Matt Willsher matt at monki.org.uk
Tue Jun 24 13:46:02 UTC 2008

On Tue, Jun 24, 2008 at 12:27 PM, Dave Cridland <dave at cridland.net> wrote:

> On Tue Jun 24 11:31:25 2008, Matt Willsher wrote:
>> While on the subject of routers/modems, I've been looking for a basic
>> modem
>> (not router) for a while but not been able to find one that I'm sure will
>> do
>> the job. I'm after something with a good ADSL/ADSL2+ chipset and allows
>> half-bridging (Firewall>PPPoE>modem>PPPoA>ISP
> Most "routers" will do that job.
>   or
>> Firewall<DHCP<modem>PPPoA>ISP).
> And that's basiclly a product of Evil Bridging, and is basically acting as
> a router.
>   The modem musn't expose itself to the
>> internet
> That will happen in the second case.
>   and I'd like SNMP for monitoring, preferably with the ability to
>> monitor line quality etc. in addition to the usual MIBs. Any suggests
>> gratefully accepted.
> AFAIK, RFC 2662 and RFC 4706 aren't available with NET-SNMP, but those are
> the ones you probably want.
> http://tools.ietf.org/wg/adslmib/ is the (still active) working group
> making those, and apparently implementations of at least 2662 do exist. I
> suspect you'll find those are provider-side, though.
> Let me know if you find something.
> Dave. (Cheerfully still using an original Speedtouch slug).

Perhaps I should have approached my request my saying what I'm trying to do.
I'm trying to get the most effecient connection for the following:

1. IPv6 - my ISP can offer IPv6 over the wire with PPPoA, so no need for
tunnels and loosing packet space to tunnel headers
2. Linux firewall/router/QoS to handle the connection. I don't want a
router/modem to touch the data.
3. I want to graph SNR, connection speed, FEC errors, packet loss etc.
4. I want to be able to transition to ADSL2+ without having to replace the

Possible solution I've come up with/tried so far:

A PCI ADSL card would satisfy most of that, but I've not been able to find
an ADSL2+ PCI card.

PPPoE to the ISP works, but it means an 8 byte loss per packet to the
header, which
I'd like to avoid for fragmentation and bandwidth usage reasons.

I can do 3 by polling the modem's web server if it gives such information or
via telnet (my Zyxel allows for this, buts it's not really ideal). I'd not
seen the RFCs you mention, but I think you're right, they're going to be in
headend ISP grade stuff. I'll have a dig around.

What I'm after is a modem that will let me use a full 1500 MTU and stay out
of the way and just do the Ethernet/ATM bridging and lets me check how it's
doing. I think perhaps I'm looking for something that doesn't exist and that
PPPoE is the most 'correct' way of going about it.

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