SSH seems to be blocked by my ISP (Free.fr).

I have several sites hosted by GoDaddy (Linux deluxe shared hosting with cpanel.) I have enabled SSH access and installed my public RSA key. My computer is connected to my router with an ethernet cable. But whenever I try to SSH, I get 'ssh_exchange_identification: read: Connection reset by peer'.

So I contacted GoDaddy, and they've assured me that they were not blocking my IP address.

What's strange is that when I connect by wifi, SSH works perfectly.

I have contacted Free.fr, but customer support is terrible (almost 1 h on hold, then somebody finally speaking for about 15 s, then you're put on hold again, and so on until you give up.)

Although I can use wifi to SSH, I'm curious about what's going on and wondering if there are any possible workarounds.

So if you connect to your router via wifi, everything works fine, but if you connect to your router via wired ethernet, it doesn't work? Same router, same ISP, same computer? If so, then it's clearly not the ISP blocking anything, it's a problem with either the router or the network configuration on your computer.

No, I connect via wifi to a hotspot (FreeWifi), so I'm using someone else router ('freebox'), ie a different IP address.

Edit: as a Free.fr customer, I'm allowed to use any FreeWifi hotspot (with the right credentials).

Ah, so if you use your computer to connect to a public wifi, everything is fine, but on your home network the connection doesn't go through?

Is it possible you have inadvertently added your own IP to the server's blacklist with too many failed connections while initially trying to set it up? Do you have SSH access to any other machines that you could test on?

ISPs sometimes block certain services for residential connections, but that's on the incoming port. I've never seen an ISP block outgoing connections.

That was what I suspected first. But GoDaddy insisted my IP was not blacklisted. They asked for a traceroute and later told me it could be my ISP.

Edit: There isn't another machine that I could try to access at the moment. And I've now merge all my previous hosting accounts into a single new one.

Edit2: Of course, I can *only* take GoDaddy's word.

When using soneone elses freebox, aren't you still using the same ISP free.fr? If so you would have thought ssh was blocked for that freebox too if free.fr were doing it.
Can you change your routers public IP address by powering it off and on or is it static?
Does your WiFi interface have different firewall settings to your Ethernet interface? Try disabling the firewall on Ethernet to test it.

Yes, you're definitely right. In that case, what's different is the IP.

The router has a static public IP.

About the firewall, disabling it doesn't change anything.

Not totally sure (because I made a lot of trials) but I think that I've been able to connect via SSH on the ethernet interface a couple of times, so the problem could also relates to what suicidaleggroll mentioned (too many failed connections while initially trying to set up SSH).

Edit: Could it be that my ISP is now blocking SSH traffic from my IP address because something looks fishy?

It could be they are blocking business type ports.

How much does it cost for an ISP anyway?

I've never seen one that blocked outgoing connections though. That would be really annoying.

Sorry, what are 'business type ports'?

21 - FTP
22 - SSH
80 - HTTP
etc.

Any of the common services. They just don't want you hosting websites, email, data servers, etc. on a residential line, they want to charge you business rates if you're running a business.

OK, I see, thanks!

Edit: It's a shared hosting so, AFAIK, there is no way I can change sshd config (including port number) on the server.

Try connecting to another remote ssh server from your home network. If you succeed in establishing a connection it will be clear that your ISP is not blocking, and more likely that the problem really is GoDaddy despite their denial. On the other hand if you are unable to ssh in to other sites then the problem may be your ISP or it may be something wrong with your own network configuration (or your ssh configuration).

If you don't have access to another ssh server you can set up a free Linux or Unix shell account for this purpose at one of the sites listed here:
http://aruljohn.com/freeshell/.

Just tried out. What I get is:

Edit: I just set up the password so I *know* it.

Ha ha. Same thing happened to me when I tried it last night. They have a very unintuitive 2-step registration process. First go to picrofo.com which brings you to their homepage, logged in as guest. Click on [Login] and set up your username and password there.

Then go to linuxshell.picrofo.com, choose one of the available shells (CentOS 6.5 or Ubuntu 14.04 LTS), click on Register, enter the same username and password that you already set up at the homepage and you should now be able to log into the shell in your browser window.

Now you can log out of that shell and try to connect by ssh from a terminal. It should work, although you might have to wait a while until the "too many authentication attempts" ban times out. I don't know how long that takes. Good luck.