External IP Address Conflict

[Enigma]

Hi! I am a "veteran" Telus user. I noticed around 2 months ago that I had an external IP address conflict between my computer, router, and Linux server. However, there could be more devices involved. Things run fine, except for cron service on my server, which doesn't work. I partly believe it doesn't work because of this conflict. The internal IP address are fine, but my external IP addresses are all same. I did multiple IP address releases, but each time I keep having this problem. Does Telus assign same IP Addresses for multiple users, or is this an incident? Thank you.

[rc · Accepted solution]

Assuming all your devices are connected the router, and the router is not in Bridge mode, then when when viewed from the Internet they will all have the same iP address.

The public address will be the router address while each device connected to the router will have a different private iPhone address.

[Nighthawk]

Your external IP will be assigned to the modem/gateway itself. I'd be surprised if you had a conflict there. In the exceedingly rare case that occurs a simple reboot of the gateway would be all that's needed to fix it. Are you sure it's not an IP conflict between your devices on your network? Is your router set to DHCP? Does your linux server have a static IP address?

[Enigma]

https://pastebin.com/7X5bW7Q0

Sorry. This site says "forbidden" when I try to send my reply.

[rc · Accepted solution]

Assuming all your devices are connected the router, and the router is not in Bridge mode, then when when viewed from the Internet they will all have the same iP address.

The public address will be the router address while each device connected to the router will have a different private iPhone address.

[Enigma]

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@rc wrote:

Assuming all your devices are connected the router, and the router is not in Bridge mode, then when when viewed from the Internet they will all have the same iP address.

The public address will be the router address while each device connected to the router will have a different private iPhone address.

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My modem is not in bridge mode. Then how do I access my server remotely? How can I make my IP Address different? Can I still access my computer remotely with same external IP addresses?

[Nighthawk]

Remote access will be heavily dependent on which ports the server is using as a number of them are blocked. Also it'll depend on how you configure port forwarding on the router so that traffic is routed to the right device on your internal network. It can be tricky.

Here is a list of the ports that Telus blocks incoming traffic on:

TCP 21 (ftp)

TCP 25 (smtp)

TCP 80 (www)

TCP 110 (pop3)

TCP 6667 (ircd)

TCP/UDP 135-139 (dcom and netbios)

TCP/UDP 443 (ssl)

TCP/UDP 445 (ms-ds)

TCP/UDP 1433-1434 (ms-sql)

[Enigma]

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@Nighthawk wrote:

Remote access will be heavily dependent on which ports the server is using as a number of them are blocked. Also it'll depend on how you configure port forwarding on the router so that traffic is routed to the right device on your internal network. It can be tricky.

Here is a list of the ports that Telus blocks incoming traffic on:

TCP 21 (ftp)

TCP 25 (smtp)

TCP 80 (www)

TCP 110 (pop3)

TCP 6667 (ircd)

TCP/UDP 135-139 (dcom and netbios)

TCP/UDP 443 (ssl)

TCP/UDP 445 (ms-ds)

TCP/UDP 1433-1434 (ms-sql)

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Okay. Thank you for the list. I needed it. But my primary question is: I have an external IP Address Conflict, and how do I access my computer from outside? Sorry if I wasn't clear on my question. I did port forwarding before when I didn't have this conflict, and it worked. But, suddenly, I wasn't able to connect anymore. Since then, I had the conflict. Thank you.

[Nighthawk]

Let's try a different approach. What is the exact error you are seeing including any error numbers, and on what device are you seeing it?

[JTL]

Do you know what NAT is? 

[rc]

How are static iP addresses assigned to your internal devices?

Assigned by the router's dhcp server or manually configured on the individual device. 

[Enigma]

Okay. I was using my server for Minecraft, however, I have decided that I will use it for hosting my website. I will just avoid the ports Telus blocked.

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@Nighthawk wrote:

Let's try a different approach. What is the exact error you are seeing including any error numbers, and on what device are you seeing it?

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I was using my laptop, and my friends said that they could not connect my server. I checked my server, and I wasn't able to connect.

[Enigma]

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@JTL wrote:

Do you know what NAT is? 

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No. I researched it, and it shows that it enables my devices to have a private and public IP Address? Okay. So is NAT causing IP Address Conflict to solve this IPv4 shortage?

[Enigma]

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@rc wrote:

How are static iP addresses assigned to your internal devices?

Assigned by the router's dhcp server or manually configured on the individual device. 

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My IP Addresses are DCHP. They are assigned by my router. Should I configure my server to have a static IP?

[JTL]

> No. I researched it, and it shows that it enables my devices to have a private and public IP Address? Okay. So is NAT causing IP Address Conflict to solve this IPv4 shortage?

Exactly. As long as the NAT "conflict" is done by your router it's usually not something to worry about.

[Nighthawk]

I think you are mistaking an IP address conflict for something else. Your external IP address will be the same for ALL devices connected to your router. That's how a router works. No problems there. DHCP employs leases for IP addresses so simply rebooting your router means you get the same IP back and in most cases renews the lease. If you left it unplugged for a few days you may get a new IP depending on how long the lease period is.

I would not recommend running a server unless you know how to correctly configure one, including being able to secure it, as well as how a router, DHCP, NAT, etc. all work.

A web server uses port 80 by default and so do browsers when trying to connect to a domain. If using a different port, users trying to connect to your server will need to include the port # in the address / URL. Telus blocks port 80 by default on residential connections. You'll have to use a different unblocked port on the router to forward to port 80 for your server's IP. 

• Can you access the server from within your network by entering the linux box's 192.168.x IP address in your browser? If no, your server is not configured correctly. This will be the first thing you'll need to test / fix before doing anything else.
• Which Telus gateway are you using? (copper or fiber?)
• What router (if any separate from the gateway) are you using? If you are us
• What port number do you have forwarded from your router to the server's IP?
• Try https://www.yougetsignal.com/tools/open-ports/ and see if the open ports include the one you set for the server. If the port you set on the router isn't open, go back and reconfigure the port forwarding on the gateway.
• For the web server, are you using Apache or something else? Disable SQL unless you really need it / know how to secure it.

[rc]

The answer is it depends on what you are trying to accomplish and what the applications require.  Some applications can pass through a nat firewall using upnp (and other techniques ) to enable multi-player games etc to work.

If you are settling up a server (ie  mail) then you will be using port fowarding (or bridging ) to a static address.

As mentioned in above posts if you are not a experienced Unix system administrator you are opening your network to hackers.

[Enigma]

Thank You!

[Enigma]

Wait if all public IP Addresses are same, what IP Address should I use? Do I just use my external IP? Thanks.

[Nighthawk]

Public IP addresses are not all the same. There are 3.7 billion IPv4 addresses in use currently, plus the new IPv6 ones. You only have one IP that is assigned to your modem. Focus on that one only.

Again as I mentioned before, unless you are sure of what you're doing and the technology involved, it is not recommended for you to run a server. IP addressing is a very basic concept in IT. If you're not familiar with IP addressing, how IP addresses are assigned, IPv4, IPv6, static vs dynamic IPs, WAN vs LAN addressing, etc, you are going to run into problems. Telus does not support servers on residential accounts so you will not be able to get any assistance from them on this. 

If you are intent on proceeding and opening up your network to security risks, please answer the questions I posted earlier.

[Enigma]

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@Nighthawk wrote:

Public IP addresses are not all the same. There are 3.7 billion IPv4 addresses in use currently, plus the new IPv6 ones. You only have one IP that is assigned to your modem. Focus on that one only.

Again as I mentioned before, unless you are sure of what you're doing and the technology involved, it is not recommended for you to run a server. IP addressing is a very basic concept in IT. If you're not familiar with IP addressing, how IP addresses are assigned, IPv4, IPv6, static vs dynamic IPs, WAN vs LAN addressing, etc, you are going to run into problems. Telus does not support servers on residential accounts so you will not be able to get any assistance from them on this. 

If you are intent on proceeding and opening up your network to security risks, please answer the questions I posted earlier.

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Thanks for the help but, I don't think I need to improve my security of my server now. That is a topic for another thread. Again, you help has helped me. I didn't know that all my devices on my networks have the same external IP Address. My server is accessible from the web. Sorry for the late reply. Happy new year!

[Enigma]

Thank you! I didn't know that all of my devices on my network had the same external IP Address. I tried connecting to my web server, and it worked. Thanks for the help. Happy new year!