IP Address & Router Problem

Netgear / Fvs336g
September 18, 2009 at 08:30:51
Specs: XP, 2GB
Hi Everyone.

I have a static IP but why is it that my router picks up the ISP cable modem (virgin media) local IP address?

The router looks like this:

IP Address:
Subnet Mask:

but when i login into the cable modem at the static IP is ok on there. The internety works fine through the router.

The only issue is that without the router using the static ip that was assigned to me it's using the cable modems which makes it impossible for me to use port forwarding.

I have also tried manually entering the static ip and subnet mask into the wan settings but the internet will just stop working. The lan is setup ok with all DHCP clients not facing any problems (

Thank You

See More: IP Address & Router Problem

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September 18, 2009 at 08:32:40
sorry, when i say: The router looks like this:

IP Address:
Subnet Mask:

I mean the routers WAN setup looks like this.

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September 18, 2009 at 08:49:15
Your isp is giving you private ip and as such you can't do port forwarding.

It would appear they are bridging their network to you vs you getting a public ip from their public ip block.

Have you gone to ipchicken.com to confirm your external ip address?

Perhaps your modem is also a router? If you can put it in bridge mode your router will get the public ip.

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September 21, 2009 at 01:12:01
Hi Wanderer, my last post.. i can't find it on my message list so i had to make this new one.

I've logged onto the cable modem and there is no option for bridging the only settings that can be changed are user names and DHCP static leases. It looks like a router though as on the information page it has the two sub-sections. Internet Settings & Local Settings.

I've just looked at ipchicken.com and the external address is appearing as it should (the static ip provided by the isp).

I have tried again to type the information in again into the router... do you think once i type the info of the IP into my router i should reset the cable modem?

Thanks for your reply.

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Related Solutions

September 21, 2009 at 10:31:03
It sounds like your Cable modem is using DHCP Dynamic IPs. You said it had reservation capabilities then Put a Static IP on your Routers WAN port and add it to your modems DHCP reservations. Do not forget to use the MAC address of your routers WAN port not the LAN port. This will make it so that your modem only give that IP to that MAC and will be a static IP.

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September 22, 2009 at 01:35:06
When you say put a static ip address in my routers wan port, what static ip address? the one provided by the isp?

My options look like this:

Index / MAC Address / IP Address / Enabled / Clear

Would this work even if the ip address as above says 192.168.0 (im referring to the "0" where my router takes it as


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September 22, 2009 at 09:21:39
ace missed the point that the modem is providing private ip to your router which results in you not being able to do port forwarding.

I take it you can't access the wan interface of the modem?

Would it be possible to plug direct to the router and not use the modem?

Unless you can or get the modem into bridge mode you will never be able to port forward with private ip.

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September 23, 2009 at 01:07:20
The address of the modem is and i can access that fine, but the options are minimal, the only real thing i can change is the DHCP reservations and parental control.

I need the modem, it's through coaxil cable that comes from underground. Then that's plugging into my router.

Would it work if i set the router instead of the local ip address of: to use (which i can also still access the router from) then see if the router will pick up the IP address from the modem?

Or is there a way i can use the modems MAC address for the router?

Do you think this is something i would need to talk to the ISP about? They are funny about this kind of stuff i.e. pay this and pay that.

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September 25, 2009 at 08:57:51
Ok your right I am a little confused. What is it that you are trying to do exactly.

It looks like you are trying to establish a DMZ between your router and the modem which would be on subnet 192.168.0.x and a Private subnet which would be 192.168.1.x so that you can configure a proper firewall? Is this correct?

Also it looks like you have put on the routers WAN port. This way the Router and Modem are on a separate subnet or DMZ. Is this correct?

The problem is as I have said above, is that if the Cable Modem its self (I have a Motorola Surfboard for my cable modem) has DHCP server turned on and your ISP (like mine) has disable the configuration functions in your modem and you will not be able to do this. Is this the Case?

The ISP does this because most users do not know how to use static IPs and to lower the number of tech calls (and becuse their tech support know nothing of networking) they enable DHCP on the modems and disable the ability to turn it off or even specify a scope.

Now if your "modem" does indeed give you the ability to do "reservations" then you are golden because a reservation will over ride a DHCP TTL and make sure that that address is always assigned to that device using its MAC address.

Did I miss any thing? Please let me know.

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September 28, 2009 at 02:34:24
Hello Ace, i just simply want to forward some ports. But im having trouble doing so because the router is taking a WAN IP address from the cable modem of

I didnt put the settings for the WAN its setup to auto-detect and when i try manual and enter the IP Address given by my ISP the internet won't work unless i put it back to automatic.

My cable modem does give me the ability for static reservations, but im confused on what information i would put in here? Do i put the routers lan IP of

The virgin media cable modem is for business so they shouldnt have limited this if they have.

You see, i have tried over & over again to port forward, the settings are ok as i've done it on many routers before but this just wont work because the netgear router is not finding the static ip addy.

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September 28, 2009 at 07:51:57
To do a reservation, you simply put in the static address (yes switch it to static) of your WAN port on the router and the MAC address of the WAN port. Yes the modem will continue to give out dynamic addresses but if it sees a device with the MAC address specified in your reservation, then it will give it the reserved address.

Now that you have a static address you can setup port forwarding on that address.

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September 28, 2009 at 08:39:27
Let's review:

can't assign a static ip address to the wan interface
can't put the modem into bridge mode.
can't port forward because its private ip not public ip
can't use the static ip given by the isp

Everyone on the same page?

ace, if medievil2003 can't assign the public ip to the router it certainly isn't going to work as you suggest putting it into the modem as a ip reservation.

medievil2003 talk to your ISP and ask them why the ip they gave you won't work when used. If you don't want them knowing its a router connect your pc directly to the modem and assign that ip to the pc nic. It very well be they want to register your pcs mac to that static ip. Let them do so. Then clone that mac to the routers wan interface and you are good to go.

Remember, that ip from the isp has to be public not private if you are to be successful for port forwarding.

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October 15, 2009 at 03:06:42
Hey, sorry i have not replied in a while.

Ok, I have been on and off the phone to my ISP and they said its nothing to do with them because the cable modem is giving out the IP address and the internet works & just because my netgear router is taking the local ip address in the WAN settings of the cable modem local settings its definetely something to do with my router configurations (says the technical team)

I was thinking, would this work:

1. The cable modem has a DHCP server and gives out IP addresses on the range between - what would happen if i changed the router's local IP address to either inside or outside the cable modems DHCP range and then try and setup the static IP address on the router?

Or then try and clone the routers MAC address?

I have at the moment tried cloning/spoofing the cable modems MAC address on the router but when i do, nothing will work..no internet, no connection to cable modem.

My ISP said to picture the cable modem acting transparent.... i thought thats rubbish, how is it transparant if its giving out DHCP address.

Help? :S

Thank You.

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October 15, 2009 at 08:54:07
Modem has a wan and lan interface. What has to happen here is the modem can't route, which is what it is doing. It has to bridge which means no lan and its wan ip is passed to the wan interface of your router.

ISP techs don't seem to comprehend the issue.

This is an ip/hardware issue and there is nothing you can do with your router or the modems dhcp server that will address your issue.

Talk to the isp again and in very simple sentences say you want the ip that is on the modem wan interface to be passed thru the modem/router to the wan interface of your router. ******You want the modem to be in bridge mode.******

Your only other option is to gain control over the wan interface of the modem router and do port forwarding there.

It would look like this:

modem wan [public ip] port forward to your routers wan ip [configure modems dhcp to only give one ip address] then port forward from your routers wan ip to your internal static ip

Alternately you maybe able to just open the port(s) on the modems wan interface then forward on your routers wan interface.

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