My network used to work.

My network is set up like this:

Charter cable modem -> my Netgear cable modem used as a wireless router -> Airlink secondary router used as a secondary wireless access point.

Things were so easy when I used my personal cable modem hooked up to Charter internet. Then Charter said I had to user their modem except it didn't have built in wireless capability. I managed to install my cable modem, Netgear CG814WG, as a wireless router. I also added a second wireless router, an Airlink 101. All was fine. I could access either wireless network from either wireless router and also access the settings from any computer in my system. Then one morning, the power supply for the cable modem quit. Unfortunately, not realizing it immediately and unable to figure out why it was nonresponsive, I hit the reset button. I waited for the lights to come back on but they didn't. Then I checked the power supply, nothing. I couldn't find another power supply and I was unable to easily open the adapter to repair it so I pulled it out of the system. The Airlink router became my main router and that's where things remained. Then I looked through my box of orphaned power supplies. I found an Epson power supply which I think fit one of my old zip drives. The voltage and current ratings matched the burned out supply so I decided to put the network back the way it was (see line 2 of this post).

Now for the part I can't figure out. If I plug the Netgear cable modem (this modem has no internet port, just four Ethernet ports) into the computer without hooking it up to the modem, like this:

Netgear wireless router/cable modem -->Computer

I can access the router's menu and settings. If I then plug the Ethernet cable from the Charter modem to my Netgear modem/router like this: Charter modem --> Netgear modem/router --> Computer it will work ok. Now I run ipconfig (Windows XP) and the ip address shown is my internet ip address, not the router ip address. Sometimes I'll restart the modem and then the correct router address will show up but then the internet connection will not work and then I can't access the router settings either. What the heck is going on here?

Thanks for your reply.

David Farber 
Los Osos, CA
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David Farber
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I don't quite understand your configuration, but I'll add a few things.

private IP address, Usually 192.168.x.x..or 10.x.x.x and one other. public IP address - The one the internet knows of

NAT - Network address translation. This part of the router. That makes it appear that your on the Internet with the public IP, Incoming ports on a port to port bases are routed to the proper private IP,

DHCP: Dynamic Host Configuration protocol - It CAN provide name server info , Your router's private IP can be the name server relay. The name server all ows you to use names for IP addresses,

It can reserve certain address for automatic generation of private IP addre sses. There cannot be more than one DHCP server for the subnet, Static IP's need to be excluded from the pool. A "lease" for a specific amount of time is associated with the address.

Certain devices behave better with fixed IP addresess: e.g. Router, printe rs

That said, there are two ways to "bridge" a network and I;m only going to t alk about one way. One allows you to be able to see the cable modem, and t he other doesn't.

If you place the cable modem in "bridge mode", by using a direct connection , it just relays traffic from network and it has a public IP, but not a pri vate IP.

In DSL, things get complicated as to where a ping response comes from. It may not include the wiring from the DSLAM to the premises.

The only way to see my modem's config pages in bridge mode is to connect it directly. I set it to a static IP of, but my network is 10.10 .0.x.

There is another address called the MAC address and that's called the Media Access Control, Think of it like latitude and Longtude, Every adapter ge ts assigned a unique one at the factory. The wireless adapter has one and so does the wired adapter on your PC. These addresses are written on the b ox and adapter. In the form of AA:BB etc for IPV4. Sometimes the : are m issing.

It's this addressees that the cable company has associated with your accoun t and credentials. You put another cable modem in it's place, the MAC addr ess doesn't match and it doesn't work. Since the lines are physical on a D SL system, the MAC authentication isn't used.

Yes, the cable modem company can be told that you have another modem and ma ke it work, but they have also customized their router;s firmware to be abl e to run tests.

So, some routers offer the ability to "clone" mac addressees. This allows your new modem to masquerade as the real cable router.

Earlier I did say that every MAC address is unique. The uniqueness is by r outeable network, So, as long as you don't duplicate a MAC address on you r private network, your OK.

I will be running at some point a very unique configuration and some of it' s in place. My DSL modem is within feet of the demarc point and the wireles s is in the center of the basement. Wireless will eventually be wireless A C with a repeater. I can't then use a any DSL modem with wireless capabili ties. Their modems limit the 10baseT ports to 100 mb/s and the wireless ports to

300 mb/s. I have a RAID server on a Gigabit ethernet.
Reply to
Ron D.

Hi Ron D,

Sorry for the delayed reply. You packed a lot of good information in there. My configuration, which was working at one point, is like this:

Starting from the coaxial wire from the wall: The coax goes to the ISP provided Cisco cable modem. My ISP now prohibits customer owned modems so that's why I'm using theirs and not my Netgear box.

The ethernet cables wired from the ISP provided cable modem to my previous cable modem which is a Netgear cable modem gateway. The model number is CG814WG v3. I only want to take advantage of the wireless capability of the Netgear device as there is already a cable modem in place.

From the Netgear box, there is an ethernet cable going to my Airlink 101 wireless router into the WAN port and that functions without any problem.

As I said before, I cannot get internet access from the Netgear box when the default ip address/gateway is After some experimenting within the *Netgear gateway/setup menu*, the ip address for the Netgear gateway flips to the ip address that is assigned by the ISP (that's what I see when I run ipconfig in XP). But once that happens, I am unable to access the Netgear setup menu but I am able to get internet access.

Ideally, I'd like to return to the condition where each router/gateway has its own ip address, be able to access both devices' (Netgear and Airlink) setup menu, and get internet access.

Thanks for your reply.

David Farber 
Los Osos, CA
Reply to
David Farber

I changed providers and had issues especially during the changeover when I wanted to switch back and forth. Finally figgered it out. Put the ISP modem in IP passthru mode. It doesn't do anything but take the ISP input and stuff it into the output. I do all the wired and wireless routing in MY router plugged into the modem.

The modem shows up in two places. The External IP address presented by the ISP and the configuration address at presented to the WAN port on my router. I can configure my router at and the modem at My router is responsible for DHCP, but I use address reservation so everybody has a stable IP address. Another secret is to use a specified destination MAC address for your IP passthru instead of automatic.

Got rid of all the multiple natting and address mixups that I had. Now, I can plug stuff in and out at most every level and it just works without any address conflicts.

When I was considering switching to FIOS, I was assured by the guru that I didn't need their modem at all. I could plug mine directly into the FIOS box on the wall. Have not tried it tho.

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You need to detach the routers other than the ISP-supplied main router, and program it/them to extend the existing DHCP services of the new main router instead of hosting their own local network(s). Or, you need to pick one main router, and change the ISP-provided unit to be a transparent bridge to that main router.

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