Restarting an Ethernet modem (ADSL) with software

[D. Hugh Redelmeier]

| From: William Case <billlinux at rogers.com>

| On Mon, 2007-04-09 at 15:22 -0500, Bruno Wolff III wrote:
| > On Mon, Apr 09, 2007 at 20:53:35 +0100,
| >   Paul Smith <phhs80 at gmail.com> wrote:
| > > 
| > > Is there some way of restarting an Ethernet modem (ADSL) with
| > > software, i.e., without switching it off and then on by hardware?
| > 
| > This is a bit off topic for this forum (unless the modem is running Fedora).
| > 
| 
| Yea, it is OT, but, boy, would I like to read an answer.
| 
| I have a cable service provider, rogers.com, that won't talk to you if
| you have a router or use Linux.

Rogers.com isn't ADSL, it is cable TV broadband (DOCSIS).

Why do you (Paul) want to restart your ADSL modem?  Or you (William)
want to restart your Rogers DOCSIS modem?

I ask because this sounds like you have a solution in mind for some
problem and I suspect that there might be a better solution.

William: I have found that my Rogers cable modems have been quite
reliable (Lancity then SB5100).  Certainly more reliable than the rest
of their network.  When I call Rogers with a trouble report, they
often ask me to power cycle the modem but it has almost never makes a
difference.

Paul: what is the problem that you expect to fix by power cycling your
ADSL modem?  Proper modem functionality (ADSL <=> ethernet) or
additional functionality (PPPoE <=> TCP/IP or NAPT)?  If it is the
latter, consider using a broadband router.



More detailed discussion of the division of labour in home network
components:

Each of DOCSIS and ADSL require their own modems to convert the
signal coming into your house into ethernet.

With Rogers version of DOCSIS, the modem presents a regular TCP/IP
ethernet access to the internet to the in-house network.  With one
globally-routable IPv4 address.  (I have heard that they will let you
have more IP addresses for a fee.)

Most home ADSL connections use PPP over Ethernet protocol.  This
peculiar protocol needs to be converted to give you a normal TCP/IP
ethernet connection.

Originally, ADSL modem boxes did NOT convert PPPoE to TCP/IP ethernet.
Customer computers were expected to do this conversion.  Our local
ADSL provider provided software for Windows boxes called "Access
Manager", quickly dubbed "Access Mangler".  On Linux, several versions
of PPPoE support existed.  Fedora has this support.

Newer ADSL modems seem to auto-detect if the machines expect PPPoE or
TCP/IP.  They seem to implement PPPoE and NAPT (Network Address
and Port Translation) as a bundle.

My guess is that the modem function is fairly reliable but the rest
(PPPoE decoding, NAPT) is less so.

For most people, a broadband router is useful as an intermediary
between their modem and their modem (ADSL or DOCSIS).

- broadband routers usually know how to do PPPoE

- the typical router is an inexpensive turnkey box.  It should require
  little maintenance and "just work".  Unaffected by computer upgades.

- it allows multiple computers to connect to your LAN by using NAT
  (NAPT really).  Most have built-in switches allowing 4 computers
  to be directly connected (more with external switches).

- it protects your LAN with a simple firewall (mostly: because of
  NAPT, by default (i.e. without port forwarding) all communication
  with the internet has to be initiated from the LAN side)

- many broadband routers include an 802.11g wireless access point

- most service providers will support broadband routers more willingly
  than Linux (most of their MS Windows customers use them too).

A broadband router isn't needed if you only have one computer and you
trust its firewall.  A broadband router isn't sufficient if you have
gateway policies that it cannot implement.

If you have ADSL and a broadband router, I recommend not letting both
do NAPT.  Double-NAPTing is pointless and can cause problems.  That
may mean that you have to use the router's PPPoE implementation and
not the modem's.