Hi there I have an unusual problem, (I think), regarding my ADSL connection. I will try to give as much background as possible.

First off this is in a corporate environment so I have frustrated users (and boss!) after me.

Here's a diagram of my current setup:

Internet -- adsl modem -- Linux server -- switch -- LAN clients

The ADSL modem is NOT a router. The linux server is an IBM eServer xSeries 335 wtih Linux Mandrake MNF on it (Kernel 2.4.18-8). This server is a firewall (iptables,) router, gateway, DNS server, proxy cache and DHCP server for my Lan clients (mostly Windows XP professional clients).

Now most of the time, everything works great.

However, some mornings I come in to work (about 1 or 2 times per week) and the Internet connection is not working. However all other (internal) network activities do work, like DHCP and network printing.

Logging in to the server and issuing a "adsl-restart" or "adsl-stop/adsl-start" has no effect (the adsl appears to think it is connected fine.) We use to have a hardware router before acquiring this server, and this problem never happened. The only way we have found to get the Internet back on is to reboot the server. Obviously I don't think this is an acceptable solution.

We have tried, restarting squid (no effect), restarting the adsl connection (no effect) and restarting named (no effect). I dont know if this is related, but my MNF operating systems seems to have automatically configured crontab to issue an adsl-reconnect.sh script every five minutes. However this doesn't seem to affect normal browsing.

Any other suggestions are welcome!!!

is your asdl modem set as a dhcp server to your linux server? I am running the same setup Internet ----> ASDL Modem ----> LInux Server -----> Switch -----> LAN Clients. My modem has a static internal IP (say 10.0.0.2) and gives eth0 (1st NIC on server) a dynamic ip (somewhere betwen 10.0.0.3-10) then my linux server runs as a dhcp server out of eth1 to the LAN. Anyways not sure if that makes sense or not but I was having the same problem. I would come in and squid would be running, samba would be running but the internet connection would be off for some reason. I finally figured out that the modem was set to lease out the ip to eth0 for a certain time.
Not sure if this will help but maybe give you another avenue to check out?

Hm, interesting.... I have no idea. I know that ppp0 gets an IP dynamically from the ISP, (eth0), however I don't know how to check the modem. It isnt' a router, and doesn't handle DHCP on its own, and I can't log into it.

How did you end up solving your problem?

I have a wee bit of a breakthrough here.

I've noticed that when the Internet connection seems to go down, the log file entries change from:
to

What is IPSEC? It seems my iptables rules are dropping it. What would cause it to switch from PPP to IPSEC? It seems to happen randomly after a keep-alive adsl-reconnect.

Anyone?