comcast router, Dlink connection from outside world

Posted on 2008-11-02
Last Modified: 2013-12-14
hello experts

I have a comcast router with 2 static ip address. The comcast cable router is connected to my DLink router. My DLInk router has the IP address of 75.XXX.XXX.205
when I ping the router I get response back. In my router I made sure that the DMZ is set to forward port 80 requests to my webserver. but from intranet or internet both, when I enter 75.XXX.XXX.205 in the address bar, it just gives me error.
If I put the local lan ip address of the webserver in the intranet which is, it takes me to webserver from intranet only. What could I do.
I have already did port forwarding to for all port 80 requests.
I called the cable company but their support is useless.
can anyone help.
Question by:syedasimmeesaq
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LVL 26

Accepted Solution

akahan earned 250 total points
ID: 22862219
You say:

"I have a comcast router with 2 static ip address".

What does that mean?  It has two different WAN Ip addresses?  Can you show us a screenshot of the setup page in the router showing this?

"My DLInk router has the IP address of 75.XXX.XXX.205"

How is it getting this IP address?

"when I ping the router I get response back."

Which router?  The comcast or the Dlink?

"In my router I made sure that the DMZ is set to forward port 80 requests to my webserver. "

in WHICH router?  the DLink?  The Comcast?  The "DMZ" is a place where ALL ports are open.  Do you mean you set NAT to forward port 80 requests to the web server?  

Can you try again, explaining how EACH router is set up, both on the WAN side, and the LAN side, where each router is getting its WAN address, how it hands out LAN addresses, etc.?

And please explain what you mean when you say your comcast router has two static IP addresses.  I can understand that comcast might have ISSUED you two static IP addresses, but how does your single comcast router handle both of them?  Normally, I'd expect you to have two comcast routers, one for each IP address, and a switch sitting in front of them.

LVL 26

Assisted Solution

by:Fred Marshall
Fred Marshall earned 250 total points
ID: 22862437
In general, *depending on the mode*, a modem can deliver access for more than one public IP address.  So, if your Comcast "router" is a modem configured in that way then you could have 2 devices with public IP addresses connected to it on your side.  

Many "routers" include a switch.  That is, there are perhaps 4 ethernet ports.
You may be able to use that switch or you might as easily connect a switch on the LAN side.

Now, you plug your Dlink router into the switch and manually give it one of the static IP addresses on the WAN.  I should think this would be manual - because if you're getting DHCP from Comcast via the modem then something is wrong I would think.  .... I can imagine it being otherwise but not for now.  Don't forget to configure DNS.

Now, you plug your webserver into the switch and manually give it the other static IPP address.

So, no port forwarding for the webserver because it's connected directly to the internet - if I understand your meaning.

I guess an alternate configuration would be to put the webserver on the DMZ port of the Dlink.  That's pretty much the same as putting it on the switch unless the Dlink provides some services for the DMZ port that are useful .. such as firewall which you'll need.  Still no port forwarding for this as the device on the DMZ has a public IP address.  No ports....

If I understand ... and this is all conjecture ... it should look like this:

Comcast gateway ... cable .... Comcast modem ... "internet switch"

No NAT or DHCP in the Comcast.......

"Internet switch" ports populated like this:
.....Comcast modem providing the internet gateway
.....75.XXX.XXX.205  WAN<> Dlink Router <>LAN / DHCP on / etc.
.....75.XXX.XXX.206??  <>webserver

I had to guess at what the 2nd static IP address would be so I used .206

Now you can ping the webserver from inside the LAN at 75.XXX.XXX.206 connecting "over the internet" address space in whatever manner....

The webserver won't have a local LAN address unless you add a NIC and put that on the LAN.  But I don't see why you'd want or need to do that.


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