[ previous ] [ next ] [ threads ]
 From:  Fred Wright <fw at well dot com>
 To:  m0n0wall at lists dot m0n0 dot ch
 Subject:  Re: several messages
 Date:  Thu, 9 Sep 2004 23:30:44 -0700 (PDT)
On Thu, 9 Sep 2004, Rob Diehl wrote:

> I was having some problems with my PPPoE DSL connection being dropped 
> (using m0n0wall's PPPoE client). After several weeks and much research 
> and frustration, I believe I have found it is due to m0n0wall sending 
> out LCP packets and not receiving any LCP echos from my provider 
> (Bellsouth).

Just to get the terminology straight, it's sending LCP Echo Request
packets, and failing to receive LCP Echo Reply packets.  This exchange is
like a ping, but at the LCP layer instead of ICMP.  It's a crock that they
don't honor it, but good luck getting them to fix it.

Disabling "LCP" would disable PPP altogether. :-)

> Soo.... I found a way to disable LCP by editing /var/etc/mpd.conf and 
> setting the "link keep-alive" option to 0 seconds.
> What are the implications of disabling LCP? If my modem drops connection 
> for some reason, will m0n0wall just sit there and not ever try to 
> re-establish a connection? What if a PC requests something on the 
> Internet, will it then try to reconnect?

There are two possible motivations: detecting link loss, and defeating an
idle timer on the other end (though LCP echoes aren't necessarily
sufficient for that).  It appears that MPD is only expecting to use it for
the former purpose, since otherwise you could enable it without the
timeout (which at least isn't a documented possibility).

I don't believe MPD will do "dial on demand" as currently configured by
m0n0wall, although it has that option.

On Thu, 9 Sep 2004, Rob Diehl wrote:

> Well, out of curiosity I unplugged my phone line from my DSL modem, and 
> let it retrain and no problems. I even turned off my DSL modem and 
> turned it back on, and m0n0wall reconnected transparently without me 
> even knowing. Next, I tried leaving my modem plugged in, but unplugging 
> the phone line for an extended period of time until m0n0wall reported a 
> LINK DOWN event in the log. Then I plugged it back in and immediately it 
> re-established my connection.

Execept for the last, the PPP client and server may not have even noticed
the link loss.  That's the whole reason for periodically testing it.

When it "immediately reestablished", what did the log show about who
initiated that and why?

> Now, the interesting thing is that even with keep-alive set to 0 to 
> theoretically disable LCP echo requests, I still see "mpd: [pppoe] LCP: 
> no reply to 1 echo request(s)" and so on when the phone line is 
> disconnected. Why is this?

Continually, or just once?  It may try to "test" the link after it's
brought up.

Did you specify both values ("seconds" and "max") as 0?  That might

Of course MPD logging information is so verbose that you probably need to
change the "show last 50 lines" to "show last 50,000 lines" to see what
you want. :-)

					Fred Wright