This is something I would contact your service provider with. If you have a modem, you can hook multiple hard wires throughout your house. I may also be confused on what your saying though

Are you running you ps3 wired or wirelessly an have you setup static ip's for both your pc and ps3 and only opened ports on the ps3 ip as I had issues initially with my router being setup incorrectly resulting in my pc not working correctly due to my ps3 ports forwarding and dmz settings as I hadn't assigned them to a single ip I changed it and everything now works fine

heres a guide of how to do it

1). Disable any firewall or security features within your router

2). try deleting the PS3 browser cache and the browser's cookies.to delete the PS3 browser cache:
a) In the Playstation XMB select "Network".
Scroll down and select "Internet Browser" and Press X.
c) Press the triangle button.
d) Highlight "Tools" and press Right on the analog stick or diagonal pad.
e) Scroll down and highlight "Delete Cache".
f) Press X and select Yes.

do the following to delete the browser's cookies:
a) In the Playstation XMB select "Network".
b)Scroll down and select "Internet Browser" and Press X.
c) Press the triangle button.
d) Highlight "Tools" and press Right on the analog stick or diagonal pad.
e) Scroll down and highlight "Delete Cookies".
f) Press X and select Yes.

3). DMZ - Putting your PS3 into a DMZ (demilitarized zone) simply opens all of the ports on it.

If you have the following problems, this is likely to fix it.

Not being able to join rooms
Not being able to speak over your headset
Not being able to hear other people over their headset
Not being able to join private games
Any problems to do with connectivity to the PSN, especially if your computer will connect to the internet, but your PS3 won't.



Part 1-(On PS3)


Firstly, you will need to assign your PS3 a static internal IP address. Normally whenever a device connects to your router it will be assigned a different internal IP address. These are normally 192.168.1.2, 192.168.1.3, 192.168.1.4 and so on. Assigning a static one will ensure that your PS3 will get the same one every time it connects.

Go to the "Settings > Network Settings > Internet Connection Settings" option on the PS3 XMB. Choose whether you are using wireless or wired.

Both selections should show a page called "Address Settings". Here you will need to select "Custom". Another page will then display entitled "IP Address Setting". The option "Manual" will need to be selected.

This will display a page where customizable IP Addresses are available to be entered.

IP Address - This will need to have the Static IP address in it. Use 192.168.1.80, simply because it is unlikely that 80 other devices will be connected at the same time.

Subnet Mask - always set to 255.255.255.0

Default Router - Is the internal IP Address of your router.

To get the exact ip of your router you should go to
Start
Run
cmd [Hit Enter]
Type in ipconfig and hit enter, this should come up with all the ip addresses to do with your computer and the network. The address you will need to enter in this option is listed as "Default Gateway".


Primary DNS - Same IP Address as "Default Router"
Secondary DNS - Same IP Address as "Default Router"
Proxy ********* When you get to the proxy screen, select "Do not use Proxy"
MTU ********* Automatic
UPnP ********* Enabled



Part 2-(On PC)


In your Internet Browser, type the address of your default gateway, this will take you to your Router Configuration Page. Look for any mention of DMZ
When you have found this, it will ask you for the Static IP of the DMZ host. This is simply the Internal IP that you assigned your PS3. We used 192.168.1.80.
Finally, turn off your Router, PC and PS3 for a few minutes to ensure that the new settings are loaded. Then your ready to go!


4). IF you dont want to DMZ your ps3 then you can assign static ip as above then port forward the cod ports and it should work better than it is at the mo but not as good as a DMZ.

black ops uses ports 81, 3074, 3075, 3478 (UDP) and port 80, 81, 443, 3074, 5223 (TCP)

id assume that mw3 would be the same

Hope this helps mate

Just reset your router/modem then connect it again and it should work other wise look on google for how to allow your ps3 ports through your router