ADSL Modem and Router

[LordEric02]

Here's the situation:

I have my computer hooked up to a Linksys wireless router which is in turn connected to my ISP's ADSL modem which is obviously connected to my phone outlet :) The problem is, when I have them connected this way, my computer does not receive a correct IP address from the modem and I get the message for limited or no connectivity. If I take the router out of the equation and plug my computer directly into the modem it works fine. This is frustrating for two reasons: 1.) I would like to be able to connect multiple machines to this DSL line. 2.) This configuration has worked in the past, baring some frequent loss of connection problems cause by (I'm assuming) the router.

Steps I tried to take:

I went into my router's settings and disabled DHCP, I figured there was no reason to have my router assign my computer an IP when the modem is already doing that. Unless of course I'm wrong and the modem only assigns the router an IP. Even if this is the case and I am wrong in disabling DHCP on the router, what else do I need to look at to get this configuration going again?

Your help is appreciated and let me know if you need more information.

[classicsoftware]

Your DSL modem is acting as a DHCP server as well as the router. You will need to speak to your ISP about putting the modem into bridge mode...

[Variable]

You could also try setting the wan side of your router to DHCP.

[LordEric02]

I'm not sure I understand what you mean by setting the wan side of my router to DHCP.

As of right now, I have a new DSL model from my ISP, they changed the password on me so I can no longer change any of its settings. I did manage to get the router hooked up and working though. The only problem is periodic disconnects. If I continuously ping my modem, I get a steady stream of 1ms replies except for about once a minute, I get a Request timed out. Then once every five to ten minutes, I get a whole string of request timed out. Usually at least a minute's worth, before the connection picks back up. Then the cycle repeats.

Any thoughts?

[LordEric02]

Also forgot to add:

If I ping both my router and my modem at the same time with the -t command, when my modem gives me the 'request timed out' my router shows nothing but solid connectivity. But I do know that if I take the router out of the equation, then my modem will give me no problems with no dropping of connection.

[classicsoftware]

Your DSL modem is acting as a DHCP server as well as the router. You will need to speak to your ISP about putting the modem into bridge mode...

This is the answer to your problem. Your DSL modem is also functioning as a router. Until you resolve this issue with your ISP, you will continue to have problems.

[LordEric02]

Ok, I guess I was just trying to avoid the stupid service fee that accompanies the call to my ISP. $50 for them to come to my house and change a few settings that I could have done over the phone with them.

[Variable]

If you cannot get into the modem and they charge you for help.
All you need to do is make the routers WAN side (the internet port connected to the modem) gets it's IP address via DHCP from the modem. On the routers LAN side (your computers are plugged into the routers switch ports) also do DHCP. It will work just fine. If the modem is doing one to one NAT it won't matter, if it is doing NAT like a router and your router is doing NAT, then you can have issues opening ports up for certain applications or for hosting online games because you have to configure the port forwarding on both devices.

Dropping a ping is not a big deal, the modem could simply have ICMP filter rules that drop ICMP requests after so many happen within a certain time.

Do a speed test once it is up and running. If speed is fine there is no issue.

[LordEric02]

I did have my modem and router setup as you suggest, and I still get regular connection drops. When I said I lost a ping I realized that one here and there isn't a big deal. But not only did I lose a ping but my entire connection went down. I could be browsing the internet and suddenly lose all access to any web page for a few minutes until the connection picked back up again.

I'm not sure what my ICMP settings are right now since I'm at work, but I'll check it out when I get home.

Thanks.

[Variable]

That could indicate a problem with physical connections or devices or TCP/Ip stack.