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sasllc
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How to connect to a PC moved to the local LAN from a static IP

First, I am assigning this to "Networking" like other dns2go questioners have done, but if there are better topics to assign it to please advise!


I have a simple setup in my office with three PCs running DCHP on a Comcast router.  No server, no domain, everything straightforward simple.


I also have a PC on a static IP address of xxx.297.242.67 we lease from Comcast that is running Robo-FTP server for about 100 clients who back up to this PC.  That setup has been working fine for years.  But I need to change to a different ISP who does not offer static IPs so I am trying to find a way to make that work.


When I set up a Robo-FTP client I do not use the static IP address of xxx.297.242.67 because I subscribe to the dns2go.com service.  I "could" use that static IP address, but the address xxx.dns2go.com we use from dns2go is easier to remember--plus it worked very well for us when we moved from one city to another where the static IPs were different.  This is because the dns2go service running on this PC connects to the dns2go server using our current static IP address.


(If it would help for me to provide our full static IP address and dns2go name, first I just need someone to tell me if that is considered legit (and safe) here on E-E .)


So this backup PC is currently configured for its static IP xxx.297.242.67 and that's what the dns2go server sees as well.  The first thing I tried was to configure the network card for this PC to DHCP like all our other PCs, and indeed it gave it a 10.1.10.x address.  Then when I checked the status on the dns2go server it showed an IP address for this PC at xxx.297.242.70 which is our gateway address.  The dns2go service on this PC connects to the dns2go server just fine.


But the problem is that the Robo-FTP clients can no longer connect to my Robo-FTP server.  So I sent a tech support request to dns2go.com asking if this should still be able to work without a static IP...because I thought that was the whole point of a service like dns2go, where it could "find" the PC no matter what it's IP address is.  Below is their response:


Yes, you should be able to utilize a dynamic IP address assigned by your ISP for what you are describing.

 

Where is the static IP address you are paying for presently configured?

 

On the backup PC or on a public interface of an Internet router?

 

What protocol does the backup process utilize?

 

What ports TCP and/or UDP does the backup process utilize?

 

The only reason why it might not work is if your ISP blocks certain inbound ports on dynamically assigned IP addresses.


After they asked me about protocols and TCP and UDP info, I wrote to Robo-FTP tech support and they gave me that info.  But now it occurs to me that no matter what those answers are, it seems like it should still work with the PC now on my local LAN since it worked when it was assigned to the static IP.  Is that correct?


And then they said that the ISP might block certain inbound ports in dynamically assigned IP addresses, I don't understand how I would find that out.  I do know there is no firewall turned on in the Comcast router, and during my testing I had the Norton firewall turned off on this PC.  Of course I could assign a static IP in the 10.1.10.,x subnet but I can't imagine that helping...right?


Furthermore, even if I find someone at Comcast tech support who can figure this out, my end goal is for this to all work with a different ISP who offers nothing but dynamic IP addresses, and worse yet it is in a city 1000 miles away--so if I ship it there and it doesn't work I'm up a creek.


What I'm really hoping that someone here can make sense of all this, and tell me not only how to get it working here on my current Comcast setup, but helping me insure that it will work with the ISP 1000 miles away--and how to do so.  Or if the whole thing is hopeless without a static IP then I need to know that.  TIA








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sasllc

8/22/2022 - Mon
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Lee W, MVP

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sasllc

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I believe the ISP being currently being used at our office far away in Shallowater TX is Spectrum.  My staff member our there asked about static IPs was told no way no how since her office is at her home address.  

I have not yet called Comcast about the constraints they may be imposing.  Even if I do find that they are doing some blocking, will they have the option to NOT block.  And same with Spectrum.  Or are these rules that they will have no control over?

Below is what Robo-FTP said back to me:
~~~~~~~~~~~~~~
Robo-FTP Server supports numerous protocols: FTP, FTPS, SFTP, HTTP, and HTTPS. You may be using one or more of the above (different clients could be using different protocols).
By default, each of these protocols uses the standard TCP port (you can find what the standard ports are with a quick Internet search). However, that is configurable. You can determine what ports you are using for each protocol by looking in the Robo-FTP Server Console. Look in the "SFTP Server" section for SFTP and in the "FTP Server" section for FTP and HTTPS (in the General Settings) tab. You can find the ports for FTPS and HTTPS in the "FTP Server" section in the "SSL Options" tab.
~~~~~~~~~~~~~~
Please give me an idea of what you would ask of a good tech support at Comcast or Spectrum in terms of what they might be blocking--and could conceivably unblock.  I know YOU understand what is going on, but I don't want to end up in a situation of "the blind leading the blind" and getting nowhere...so I need your guidance on what to ask.
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Lee W, MVP

I would call spectrum again and tell them you're operating a home business and need a BUSINESS CLASS line at that address.

What I'm trying to get across to you is that the ISP (especially if it's spectrum) is a behemoth of a company.  You may be told by the person on the phone that it's no problem, nothing is blocked.  You may even try to verify with them and the person you speak to might re-iterate that nothing is blocked.  Then you get the line installed and guess what?  It's BLOCKED.  And then you call up and explain a third (or a fourth, or a fifth) time and they then tell you "sorry, we don't have that option on home accounts" or something like that.  I've tried verifying things with Cable companies before.  I tried verifying with Spectrum that the copy once flag was NOT enabled on cable card accessed programming.  I was assured it wasn't. Guess what - it IS.  And they won't do anything to change it for me - I'm a speck to them.  

Put another way, there are some companies you can call - some circumstances where it doesn't matter much - and verify a feature/capability is present.  The Cable Television/Internet industry has a HORRIBLE reputation for a reason.  Verify all you want, *I* still wouldn't trust it until you've actually got it running and it works.

Now, that said, they don't block all incoming ports. It sounds like (and I'd be surprised if it weren't the case) that Robo-FTP allows you to run things off different ports.  As long as you don't use another well known port (see here: https://en.wikipedia.org/wiki/List_of_TCP_and_UDP_port_numbers) you can probably use any other port number to host the server.  HOWEVER, doing so would require re-configuring all your endpoints to alter their connection address (dns2go can be used to make the IP switch easy, but *IF* the ports are blocked, it won't translate those for you, you'll need to adjust them manually on all clients).

The internet is a dangerous place.  And while they don't (yet?) do this, I wouldn't be shocked if EVENTUALLY, some ISPs decide they want to block ALL incoming ports for home uers.

BTW, a quick googling of Spectrum Blocked Ports finds this: https://www.spectrum.net/support/internet/blocked-ports/
It would SEEM they don't touch the various FTP ports.  But again, *I* don't trust them.  CONFIRM IT FIRST by actually using it successfully!
sasllc

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It did not occur to me to set up port forwarding in the router, so I will try that next.


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