How to find what ports are open/blocked

[#1]

I have a technicolor TG582n router.

How can I find out what ports are open and blocked (TCP, UDP)?

I need to get Skype for Business working when I work from Home and there's a suggestion that the firewall maybe blocking a port.

Cant find anything on the search unless its about port forwarding, whatever that is.

Thanks

[#2]

Run a full shields up scan (google for shields up)
That will tell you if any ports are open.

But you shouldn't need to open any to use Skype. Unless you have disabled UPNP on the router?

[#3]

OK, thanks Hairy,

I'll give that a whirl.

Ive not made any changes to the thing, never needed to.

[#4]

I assume you are on windows, check your LOCAL firewall isn't blocking it.

[#5]

Yes, I'm running windows 7.

Specifically the prolem is that Skype for business on my work laptop does not connect to the server when I VPN in to the office.

However it does work if I am in the office and disconnect from the LAN and VPN in to the office.

Which made IT Support suggest that my home firewall was the problem. I did a shields up test and it was all good.

[#6]

Right a vpn complicates things.
Try without the VPN connected, if skype connects then it is a setting in the vpn that needs checked. If not disable your pc's firewall and try again.

[#7]

Skype for business won't work without the VPN, because the server is in a cloud that can only be accessed from within our organisation and I can only get inside our organisation via the VPN.

I also cannot disable the FW on the laptop because that is locked down by the administrator. 

The fact that SFB works from within the organisation via the LAN or via the VPN would suggest some external influence when I try via the VPN at home - the router (at least that's the theory they are working on)

[#8]

What subnet does your corporate VPN use? I wonder if there's overlap with the IP's the Hub One assigns to the LAN.
When connected to the VPN, open a command window, type 'ipconfig /all's (minus quotes) and press enter.
What's returned?

[#9]

Bob, I don't know, TBH I think this is an infrastructure issue and I'm inclined to let our infrastructure team deal with it, but as we're in the process of outsourcing our infrastructure they are not being overly helpful as they all know that redundancy is looming.

It will be resolved in due course. It's just that it should work and it works for other users, but not on my laptop for some reason.

[#10]

I have a NAS and its reporting hacker attacks from Russia that are failing due to repeated password violations.  That means they are getting through the router firewall using the remote signon port.  I have in the past used the NASs remote signon service and I suspect that has left a port open.

How do I find out what ports are open on my plusnet hub one?

If I want to close a port number how do I do that?

Can I set the firewall to block anything coming from a specific IP or range of IP addresses?