I recently moved and my only broadband solution at the moment is Bellsouth FastAccess DSL (bellsouth.net).
I had been using Comcast cable-modem for several years prior to this with no difficulties at all. I took all my equipment
as-was to the new house. The only variable here is the change from cable-modem to DSL.
The DSL modem is a Westell 6100 in PPPoE mode and it provides NAT and DHCP. If I connect any single one of my PCs or laptops directly to it, everything works
perfectly. My net connection stays up 24/7. The problem begins when I put my firewall/router (Netgear RP614v2) in the loop between the DSL modem and my LAN. At first, everything
works great. Then within 10-15 minutes I simply lose connectivity to the Internet. When this occurs, it fails in one of two ways:
1. I can no longer access the DSL modem interface (192.168.1.254) from the LAN, but the "Internet" light on the DSL modem is still green.
2. I can still access the DSL modem interface (192.168.1.254) from the LAN, but the "Internet" light on the DSL modem is out and when I
go into the modem's "expert" interface and look at the statistics, I see on the ATM page that the PPPoE connection is DOWN. I've left it
that way overnight and during the workday and it never recovers on its own.
Either way, if I reset the DSL modem (power off, wait, power on), everything works fine again for another 10-15 minutes. Very frustrating. :)
Here's whatI have tried and/or learned so far...
The DSL modem had the PPPoE connection set to "On Demand". I tried setting that to "Always On". No change.
I tried cloning one of my PC's MAC address to the firewall's WAN port. No change.
I read all about MTU and set that down to the first value that passed the 'ping -f -l' test (MTU = 1372, why so low?). No change.
I made sure my firewall would respond to ICMP/ping on the WAN port. No change.
The DSL modem has the latest version of its firmware for that model (verified with BellSouth technician).
I captured about 16 hours worth of IP traffic with ethereal between the DSL modem and my laptop. I saw nothing generated by the DSL modem
that looked like it would expect a response except an occasional ping (already turned that on on the firewall, see above).
I have an older Netgear FR314 firewall/router. I put that in the loop for a "second opinion". No change, exact same behavior as with the RP614v2.
Here's what I'm currently thinking...
My firewall also does NAT and DHCP for my LAN. I do have the DSL modem and my firewall NAT/DHCP set to separate subnets (192.168.1 vs. 192.168.0).
Is there some other double-NAT issue I'm yet unaware of?
Is DHCP on both an issue? Are requests to the firewall somehow bleeding through to the DSL modem and "confusing" it?
What's really bothering me is what's the difference between my PCs/laptops and the firewall as far as the DSL modem is concerned?
Is there some kind of low-level ethernet traffic that I cannot see with ethereal that PC will respond to differently than the firewall?
It's almost as if the DSL modem knows the difference between the two...
I'm looking for further advice past all this. I am a software engineer with lots of hands-on (non DSL) network experience, so please feel free to
hit me with an obscene level of technical detail and/or references. :)