Question Port Forwarding For A Server - Not Open

jtnoble321

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Hey all, been trying for a few hours on this and I am stumped.

I'm using a Netgear Router and trying to host a Valheim server. I've tried running a Minecraft server before and I believe I had the same issue.

For Valheim, you open ports 2456-2458 TCP/UDP, which I have done for the correct IP address. The IP on the server machine is NOT static, but the IP hasn't changed or anything.

I also added some Inbound and Outbound rules to open up ports 2456-2458 through the windows defender firewall. Also tried disabling my firewall, disabling any antivirus, and even making the local IP the default DMZ.

The problem is, when I type in 127.0.0.1:2457 or localhost:2457, it doesn't seem to work. If I type in [localIP]:2457, it works. Great right? You can probably guess where I am going with this.

My Public IP, lets say it's 123.456.789.01, cannot be connected to. I had friends try connecting and I tried troubleshooting through a mobile hotspot (so I didn't share the localhost).

I called my ISP and they said they don't block any ports besides known malicious ones, and they told me those ports weren't blocked. When going into the Steam server browser and typing 123.456.789.01:2456/2457/2458, it just shows up as blank. If I join the server from my gaming computer (joined on a different computer, same network), my friends can attempt to connect to my server, but they get a "Server Not Responding" error.

I know the server is up locally, but I am not sure why it isn't up publicly. Here is where I think the problem might arise, but I am unsure.

We don't go through a modem, our internet connection goes straight through the wall in our apartment.

My roommate and I both have separate routers, but upon having him check, we both share the same public IP despite being on different routers.

I wouldn't think this is the issue, but this is the only thing different from when I hosted servers before at previous locations. I tried forwarding the IP on his router too (and of course, the IP doesn't exist according to his network because it isn't connected to it), but alas, failure.

Kinda running out of options, so let me know if you have any ideas!
 

sds20020024

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Jan 23, 2019
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Okay I think this is happening because of multiple NATs (network address translation layers).
If you and your roommate have different routers but the same public IP, then both your connections are coming from another router.
You need to forward those ports on that router as well for the server to be accessible from the internet.
You don't neet a DMZ to run a server.

Also, it could be that your ISP uses CGNAT (carrier grade NAT), which is where it gives a bunch of it's customers in the same area the same public IP, but different local IPs.

If this is the case, you're plain out of luck because ISPs very rarely port forward on users' request on a CGNAT.

Check your router's WAN address. If it's not the same as your public IP, then you're going through multiple NATs.

You and your roommate are getting your connections from another router.
Most probably, that router's WAN IP is your public IP.
So whenever a packet comes to your public IP, that router doesn't know where to send it.
So it doesn't matter that your router has port forwarding set up.
The packets from the internet never reach your router.
They get turned down from the router that's giving you and your roommate the same public IP.

You said you don't go through a modem, your ethernet cables plug into your apartment wall.
Well this router that I'm talking about could might as well be the modem.

It could be that the coax cable comes in and goes into a modem that's in an electrical panel inside the wall or something, and that modem gives out two rj-45 cables that go to your router and your roomate's router.
 
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jtnoble321

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Nov 14, 2015
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Okay I think this is happening because of multiple NATs (network address translation layers).
If you and your roommate have different routers but the same public IP, then both your connections are coming from another router.
You need to forward those ports on that router as well for the server to be accessible from the internet.
You don't neet a DMZ to run a server.

Also, it could be that your ISP uses CGNAT (carrier grade NAT), which is where it gives a bunch of it's customers in the same area the same public IP, but different local IPs.

If this is the case, you're plain out of luck because ISPs very rarely port forward on users' request on a CGNAT.

Check your router's WAN address. If it's not the same as your public IP, then you're going through multiple NATs.
I tried forwarding the IP on his router too
I already tried forwarding my IP address on his router as well (even though it doesn't show up in his connected devices).

As for the WAN address, All I could find on my router's page was the default gateway and nothing that looked like a public IP
 

sds20020024

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Jan 23, 2019
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I already tried forwarding my IP address on his router as well (even though it doesn't show up in his connected devices).

As for the WAN address, All I could find on my router's page was the default gateway and nothing that looked like a public IP
Port forwarding on your roommate's router won't do anything.
As I said, since you and your roommate have the same public IP, your ethernet cables are coming out of another router (probably the modem-router that your ISP provided).
Unless you find that router and set up port forwarding on that too, it won't matter whether your router or your roomate's router has port forwarding set up, because the packets from the internet never reach your or your roomate's router.

The modem-router between your router and the internet doesn't know where to send the incoming packets when someone sends a request on your public ip on a certain port. So that modem just turns it down.
 

jtnoble321

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Port forwarding on your roommate's router won't do anything.
As I said, since you and your roommate have the same public IP, your ethernet cables are coming out of another router (probably the modem-router that your ISP provided).
Unless you find that router and set up port forwarding on that too, it won't matter whether your router or your roomate's router has port forwarding set up, because the packets from the internet never reach your or your roomate's router.

The modem-router between your router and the internet doesn't know where to send the incoming packets when someone sends a request on your public ip on a certain port. So that modem just turns it down.
So even upon calling my ISP, they told me the ports are open on their end but I've still got nothing. I assume with that there's really nothing I can do

Edit: Also my apologies, I misunderstood you when you said router, and assumed you meant my roommates router, not the modem.
 

sds20020024

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So even upon calling my ISP, they told me the ports are open on their end but I've still got nothing. I assume with that there's really nothing I can do

Edit: Also my apologies, I misunderstood you when you said router, and assumed you meant my roommates router, not the modem.
Actually no
I think you should try to find out first if you have a modem in your apartment or building somewhere which is branching out into the ethernet cables that plug into your and your roommate's router.

Most of the time , your ISP doesn't directly give you an rj-45 cable into your apartment. They give you a coax cable, which plugs into a modem or modem-cum-router, which then outputs rj-45 cables that you use.

I think this modem is somewhere in your apartment that you aren't aware of.

Once you find that modem, connect your PC directly to it, set up port forwarding for your local ip, which is your router's wan ip, ( the other local ip being your roommate's router's wan ip if it's just you and your roommate sharing the modem), and then your server will be accessible from the internet.
 

jtnoble321

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Actually no
I think you should try to find out first if you have a modem in your apartment or building somewhere which is branching out into the ethernet cables that plug into your and your roommate's router.

Most of the time , your ISP doesn't directly give you an rj-45 cable into your apartment. They give you a coax cable, which plugs into a modem or modem-cum-router, which then outputs rj-45 cables that you use.

I think this modem is somewhere in your apartment that you aren't aware of.

Once you find that modem, connect your PC directly to it, set up port forwarding for your local ip, which is your router's wan ip, ( the other local ip being your roommate's router's wan ip if it's just you and your roommate sharing the modem), and then your server will be accessible from the internet.
We connect our routers directly through the wall with an RJ-45, and I have definitely checked around and seen no modem inside my apartment. If there is one, it's in an inaccessible part of the building. If it helps, we have to register our MAC addresses of our routers on our ISPs website in order to get them working. The setup is really a little different than anything I have ever seen from an ISP.
 

sds20020024

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We connect our routers directly through the wall with an RJ-45, and I have definitely checked around and seen no modem inside my apartment. If there is one, it's in an inaccessible part of the building. If it helps, we have to register our MAC addresses of our routers on our ISPs website in order to get them working. The setup is really a little different than anything I have ever seen from an ISP.
I think in that case you should try to find out if your ISP uses CGNAT.
Trying to set up a server with a CGNAT isn't gonna happen.

Is your router's wan ip a static ip?
Did your ISP give you an IP, a subnet and a default gateway when you signed up?
If they did not, chances are your ISP is giving you a dynamic IP, and setting up a server with a dynamic IP isn't gonna work.

Your router probably runs DHCP.
Try setting up address reservation for your server that you're trying to run.
Or try plugging a computer in directly to the rj 45 cable, no router, and in the network configuration settings, set it to obtain ip automatically.

If you get access to internet, your ISP uses dynamic IP, not static IP, and unfortunately you can't set up a server with dynamic IP unless you tell your ISP to set up address reservation for you.

The fact that you and your roommate share the same public IP although you have two routers, and plug in directly to the wall seperately tells me that either both of you are getting your connections coming out of a modem, or your ISP uses CGNAT
 

jtnoble321

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I think in that case you should try to find out if your ISP uses CGNAT.
Trying to set up a server with a CGNAT isn't gonna happen.

Is your router's wan ip a static ip?
Did your ISP give you an IP, a subnet and a default gateway when you signed up?
If they did not, chances are your ISP is giving you a dynamic IP, and setting up a server with a dynamic IP isn't gonna work.

Your router probably runs DHCP.
Try setting up address reservation for your server that you're trying to run.
Or try plugging a computer in directly to the rj 45 cable, no router, and in the network configuration settings, set it to obtain ip automatically.

If you get access to internet, your ISP uses dynamic IP, not static IP, and unfortunately you can't set up a server with dynamic IP unless you tell your ISP to set up address reservation for you.

The fact that you and your roommate share the same public IP although you have two routers, and plug in directly to the wall seperately tells me that either both of you are getting your connections coming out of a modem, or your ISP uses CGNAT
I'll try plugging my computer directly into the wall and see if that does anything weird. Otherwise, I think most of what you're saying about them using CGNAT is right
 

sds20020024

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Question here though. Would bypassing the forwarding with Hamachi end up working in this case?
By Hamachi do you mean the VPN client?

I think for troubleshooting, at least for now, don't use a vpn if you can.

Btw if it wasn't clear,

How to confirm whether your ISP uses CGNAT?
Call them, or search on the internet.

About the dynamic IP thing.
How do you find out whether your ISP gives you a dynamic IP?
Plug a computer directly into the rj-45 coming out of the wall, and set the network adapter in your pc to get an IP address automatically.
If you can access the internet without entering any IP, subnet or default gateway, then your ISP uses dynamic ip.

Also while you're connected to the rj-45 cable coming from your wall directly, if you get access to the internet without having to enter an ip, and choosing ' get ip address automatically', once it does get an ip address automatically, open settings and see what ip address it got.
If that ip isn't the same as your public IP, you're going through another NAT, which again, is either a modem that's shared between you and yout roomate, or your ISP's CGNAT
 
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jtnoble321

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By Hamachi do you mean the VPN client?
Btw if it wasn't clear,
How to confirm whether your ISP uses CGNAT?
Call them, or search on the internet.

About the dynamic IP thing.
How do you find out whether your ISP gives you a dynamic IP?
Plug a computer directly into the rj-45 coming out of the wall, and set the network adapter in your pc to get an IP address automatically.
If you can access the internet without entering any IP, subnet or default gateway, then your ISP uses dynamic ip.

Also while you're connected to the rj-45 cable coming from your wall directly, if you get access to the internet without having to enter an ip, and choosing ' get ip address automatically', once it does get an ip address automatically, open settings and see what ip address it got.
If that ip isn't the same as your public IP, you're going through another NAT, which again, is either a modem that's shared between you and yout roomate, or your ISP's CGNAT
Kinda, Hamachi is like a VPN but you can connect other people with Hamachi to bypass ports.

As for confirming CGNAT, I called and they couldn't give me a straight forward answer, so I'll call again in an hour or so to see if someone else knows the answer. Haven't found anything online about them though.
 

sds20020024

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Jan 23, 2019
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Kinda, Hamachi is like a VPN but you can connect other people with Hamachi to bypass ports.

As for confirming CGNAT, I called and they couldn't give me a straight forward answer, so I'll call again in an hour or so to see if someone else knows the answer. Haven't found anything online about them though.
If you ask me , I'd say it's most probably a modem or another router between you and the internet.
Because CGNAT isn't that common. (Although CGNAT is essentially just another router between you and the internet, but one that your ISP uses to share a public ip among a bunch of its user)
So maybe ask the super of your apartment whether there is a modem into which your wall ports go?
Because I'm 85% sure this is the problem, because I've encountered scenarios like this before, and most of the time it was another router in between, or a modem that someone didn't realise was also working as a router etc
 

jtnoble321

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If you ask me , I'd say it's most probably a modem or another router between you and the internet.
Because CGNAT isn't that common. (Although CGNAT is essentially just another router between you and the internet, but one that your ISP uses to share a public ip among a bunch of its user)
So maybe ask the super of your apartment whether there is a modem into which your wall ports go?
Because I'm 85% sure this is the problem, because I've encountered scenarios like this before, and most of the time it was another router in between, or a modem that someone didn't realise was also working as a router etc
There are locked closets outside of our apartment doors, so if there's a modem it's likely in there (and our apartment doesn't let us manage that stuff)
 

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