[plug] Bridging in ADSL modems

[Craig Ringer]

Ben Jensz wrote:
> It can mean two similar, but different things.
> 
> 1.  You put your ADSL router/modem into bridged mode and you then plug 
> it into a computer which has a PPPoE client on it which handles the 
> authentication.  So basically it acts like an old 56K analogue modem in 
> that the computer controls it and handles all the authentication.

This is the more common meaning these days, as there are fewer and fewer 
bridged ADSL services around.

> 2.  You put your ADSL router/modem into bridged mode and have a specific 
> bridged ADSL line configuration (non-standard) done to your phone line 
> that doesn't have any authentication on it.  You generally lose some 
> features such as shaping with some ISPs if you do this though.

On the other hand, the reliability is incredible. I held on to my 
bridged ADSL connection until iiNet forced us off it kicking and 
screaming, despite the fact that we paid $30/month extra for it toward 
the end. Our DSL service has never been anwhere near as solid since - I 
never used to have to worry about Telstra's authentication services dying.

> Some of the reasons why you'd do the first one would be if the computer 
> you're plugging the modem into handles the authentication and connection 
> in a more reliable and stable manner than the PPPoE client built into 
> the ADSL router/modem does or if you wanted to have finer control over 
> firewalling etc. than the simple NAT / firewalls built into most ADSL 
> routers/modems.

Running your own PPPoE client also gives you better control of packet 
queuing and things like that. I've found it very helpful when trying to 
keep latency down on interactive traffic while bulk data transfers are 
running - especially when combined with a good QoS setup.

It's also much easier to tell at a glance what's wrong with your 'net 
connection. 'tail /var/log/messages' is rather easier than "examine 
blinking lights in an attempt to figure out what's going on."

--
Craig Ringer