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Port forwarding through cable modem and router

Posted on 2014-09-02
Medium Priority
Last Modified: 2014-09-06

Recently I switched to Comcast and I'm having issues getting a port forwarded through the Comcast cable modem and my EA4500 switch.

I really just don't know what to do... please help :)

Question by:prosit
LVL 22

Expert Comment

ID: 40299505
The cable modem is likely a router as well.  You have 2 options.


Remove the EA4500 from the mix and do your port forwarding at the cable modem/router


You can login to the cable modem and assign the WAN IP Address of the EA4500 to the DMZ on the cable modem or just forward all ports to the WAN address of the EA4500.  The WAN address of the EA4500 is likely a 192.x.x.x address as it is assigned from the LAN side of the cable modem.  There may also be an option to disable the firewall all together on the cable modem.  Any of these will work for what you need.
LVL 97

Expert Comment

by:Lee W, MVP
ID: 40299511
You're going to have to be more specific than that... What have you done, what are you trying to do... how have to determined they aren't working... etc.

Author Comment

ID: 40299516
1. The cable modem is a router yet, but a crappy one.  Doesn't have guest network and the range is limited at best.

2. but then the ea4500 would stay in the dmz correct?  Not the solution I'm looking for since my wireless printers are all connected to the ea4500.
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Author Comment

ID: 40299520
I want to be able to connect to a plex server from the outside running on a machine on the inside of my network.

If there's a better way, I'm all ears.

LVL 22

Expert Comment

ID: 40299538
Putting the ea4500's WAN IP address in the Cable Modem's DMZ just bypasses the firewall at the Cable Modem for your ea4500.  You still have the firewall on the ea4500 protecting your network.

You do not need two firewalls; it just inhibits performance.
LVL 23

Accepted Solution

tailoreddigital earned 2000 total points
ID: 40299723
I've dealt with this problem numerous times, but i can't remember the exact models.

Comcast has modem/routers that simply fail to do the port forwarding it's designed to do.    After going through the levels of tech support, even returning what i thought was a bad brand new router, it turned out to be a faulty modem/router from Comcast.    I don't mean i had one bad modem/router, the particular model Comcast gave my client had a known issue with forwarding, bridging, or any other feature beyond basic usage.    I finally ran across a upper level tech at Comcast that was aware of the known issue.   Why none of the other techs knew of this, i don't know.    The tech explained the problem and suggested i return the modem/router for another specific brand modem/router that Comcast also offered and is known to work with Forwarding.    Once i switched everything worked as it was designed to do (in minutes).

I spent hours/days troubleshooting this.   I wished Comcast actually had a competitor in this area, because they have no motivation to improve these crappy tech support issues.  Someone should have know this at Comcast when i initially called.   What a waste of time, thanks Comcast.

Oh and i should mention that you still could have a good device and simply not have it configured properly.   My suggestion is simply a plan B.    If you feel you have it configured correctly and still nothing, then plan B.

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