Port forwarding to more than one computer on a network?

gobrun · 17 Jun 2008 at 14:33

Me and my housemate are both on a Netgear DG834 router. It was only today that I actually discovered that ports can only be forwarded to one machine on a network at a time

rolleyes

. This is a problem...

We both play company of heroes a lot and as any veterans of the game will know Relics peer to peer game matching service is a complete joke. Right, the game requires ports 6112 & 30260 to be forwarded, this isn't a problem, I'm perfectly adept at creating firewall rules to open ports. The problem is it only opens the ports on either my computer or his computer, it can't do both simultaneously. This means one of us is left with a torrid time trying to connect to the same 2v2 CoH game while the other gets straight in because only one computer has those ports open.

I'm thinking there has to be someway to get round this? Can't you assign one IP address to every machine on the network or something? I assume this is how a standard ADSL modem thats providing internet access for two computers works? Would I need a network card with dual sockets in order to do this using a router or is it only possible with a modem?

Thanks!

tolien · 17 Jun 2008 at 14:34

You can't forward a port to more than one machine at a time, and it works with a modem because a) it isn't forwarding anything and b) there's only one IP behind it.

HarryPainful · 17 Jun 2008 at 14:50

Why do you need to forward them, just open them.

Assign 1 ip to every machine on the network.. O_o

And a standard ADSL modem will not share a net connection, one of the machines on the net work will has ICS running and NAT takes care of everything...

You would probably find the solution is pretty simple if you didn't think you know everything.

gobrun · 17 Jun 2008 at 15:08

HarryPainful said:
Why do you need to forward them, just open them.

Assign 1 ip to every machine on the network.. O_o

And a standard ADSL modem will not share a net connection, one of the machines on the net work will has ICS running and NAT takes care of everything...

You would probably find the solution is pretty simple if you didn't think you know everything.

I can't open both ports to both IP addresses at the same time. The router will only unblock ports for one IP address. (whoever altered their static IP address last in the IPv4 config).

Let me explain what happens...

I set my computers static IP to 192.168.0.30
My mate sets his static IP to 192.168.0.31

I go into network config and make four new firewall rules. I make 2 rules opening ports 30260 & 6112 for my ip address and I make 2 rules opening the same ports for his IP address.

Unfortunately the router only opens these ports for one IP address at a time, for some reason it can't do both simultaneously no matter how many rules for how many static IP addresses I input....

The best 'solution' I've found so far is to only open 6112 for me and only open 30260 for him. Problem is I don't know whether CoH requires both ports to be open or one or the other. Thing is we've tried playing a few games and connectivity is still nigh on impossible for both of us at once.

Thanks for the answers so far folks.

tolien · 17 Jun 2008 at 15:11

HarryPainful is thinking of opening as in opening in the firewall (if there is one).

Unless you're trying to host a game you shouldn't need to forward any ports but the router would probably get confused if you were both on the same server.
The point of port forwarding is to tell the router what to do if traffic comes in on that port when no machine on the network has sent traffic out.

AbsenceJam · 17 Jun 2008 at 16:06

tolien said:
Unless you're trying to host a game you shouldn't need to forward any ports but the router would probably get confused if you were both on the same server.
The point of port forwarding is to tell the router what to do if traffic comes in on that port when no machine on the network has sent traffic out.

With Company of Heroes the multiplayer is peer-peer so port forwarding is necessary as each client is also a server.

gobrun, see if your ISP offers multiple static IP's, if they don't offer that look into tunneling.

HarryPainful · 17 Jun 2008 at 17:25

Just use NAT!!

mynsa · 17 Jun 2008 at 19:29

HarryPainful said:
Just use NAT!!

i dont think you quite understand the problem.

NAT is used on the outgoing connection - otherwise how would traffic get routed back to his lan.

NAT is also used on the incoming connection to port forward the traffic. But you cant forward traffic on the same port to two ip address simulataneously (sp?).

His problem will only be solved by either using a different destination port for the incoming traffic to one of the workstations on the lan (keep other the same) or to use another public IP address for the other workstation (again would need to be port forwarded)

m_cozzy · 17 Jun 2008 at 22:30

As mentioned it probably isn't necessary to open ports just to play a game unless your are trying to host. I would have thought the router could cope with you both connecting to a game server. I dont recall having issues playing UT many years ago when my mate used to bring his pc round.

drdimmer · 17 Jun 2008 at 23:07

Why don't you use port forwarding on one IP and setup a DMZ on the other ip?

Phemo · 17 Jun 2008 at 23:18

drdimmer said:
Why don't you use port forwarding on one IP and setup a DMZ on the other ip?

Because that'll just forward all other ports to the DMZ IP. The two ports that are actually needed will just go to the IP that has the port forwards configured.

As CoH multiplayer is p2p I don't think there's anything you can do without getting multiple IPs from your ISP.

russ0r · 18 Jun 2008 at 00:43

gobrun said:
I'm thinking there has to be someway to get round this? Can't you assign one IP address to every machine on the network or something? I assume this is how a standard ADSL modem thats providing internet access for two computers works? Would I need a network card with dual sockets in order to do this using a router or is it only possible with a modem?

There is no way round this with your current setup. Because of the way NAT works, it can't forward data from one port to two computers on your network simultaneously. Not easily anyway - You might be able to do something like this with a dedicated routing computer eg. a smoothwall box... but not 100% sure.

The only other way to do it is ask your ISP for two IP addresses, so you basically eliminate NAT on your network. Probably cost a fortune in equipment and ISP fees though.

Jumping · 18 Jun 2008 at 09:16

Most Enta net resellers offers upto 8 IP addresses for no extra money and with mulitpiple IP's you wont have any problems with having to use portforwarding.

JIM_BOB7813 · 18 Jun 2008 at 10:12

If you have multiple IP addresses from your ISP, assign 1 to each machine then you will have removed NAT. (not sure about your router, but this should open all ports to each machine).

Are you sure the firewall is still operating after you assign multiple IPs? If it is, and it won't let you configure it as you want, why not just turn it off and use a software firewall while you are playing coh?

edit: Just noticed, you are assigning local IPs, you need to get 8 IP addresses assigned by your ISP.

Isn't it possible to change the port that coh uses? Because this is your only other solution as i see it.

mynsa · 18 Jun 2008 at 10:39

JIM_BOB7813 said:
If you have multiple IP addresses from your ISP, assign 1 to each machine then you will have removed NAT. (not sure about your router, but this should open all ports to each machine).

Are you sure the firewall is still operating after you assign multiple IPs? If it is, and it won't let you configure it as you want, why not just turn it off and use a software firewall while you are playing coh?

edit: Just noticed, you are assigning local IPs, you need to get 8 IP addresses assigned by your ISP.

Isn't it possible to change the port that coh uses? Because this is your only other solution as i see it.

exactly what i was saying, get another public ip address, or change the port coh uses.

no other ways around this, unless you start to specify sources, but as its p2p its very unlikely you will know the source ip addresses in advance.

drdimmer · 18 Jun 2008 at 22:21

Phemo said:
Because that'll just forward all other ports to the DMZ IP. The two ports that are actually needed will just go to the IP that has the port forwards configured.

As CoH multiplayer is p2p I don't think there's anything you can do without getting multiple IPs from your ISP.

Ah I'm an idiot.... sorry!