Port Forwarding and Loopback with HomeHub 3B

Question

There have been a number of threads discussing port forwarding and loopback, so I thought it might be useful to summarise my experiences. I have two HomeHub 3Bs on separate lines, one is a standard broadband line, the other is on an Infinity connection. My experience is limited to these two specific devices :-)
Port Forwarding does work but it is "temperamental" and "arcane" in the way you need to set it up. Although I have had it running perfectly, I have also had experiences where the router has refused to "accept" my changes. Tentatively, I put this down to the fact that I was running a Seagate GoFlex network drive on the network and this piece of equipment (definitely a Do Not Buy) was acting aggressively and screwing up the DDNS allocations. But ... YMMV
One definite probllem with Port Forwarding is if you attempt to specify a range of addresses. I have failed to get this to work on both my hubs. In my case I was trying to forward (say) 8021-8022 to 21-22, and the router insisted on forwarding both 8021 and 8022 to port 21.  The cure is to set up each port as a separate rule within the same user-defined application.
On Loopback, I know various people have said it doesnt work, but it has always worked fine for me, at both the locations where I have a HomeHub 3B. I use a DDNS service and I can test that my port forwarding is working by opening a Command Prompt window on my PC and typing  telnet mydomain.dyndns.web.com 21 or whatever. That command contacts my DDNS host to ascertain my IP address and then (attempts to) connect to port 21.
If port 21 is closed on your router (i.e. you have no port forwarding in place) you will see the message attempting to connect to mydomain.dyndns.web.com... and, after a while that will time out, with Could not open connection to the host, on port 21: Connect failed. If you do have your port forwarding set up correctly then your application will respond in some appropriate mannerr. However, you do need to understand what youre doing, because the response of an application that is expecting HTTP data is simply to do nothing!  You will probably get a blank screen. If you type GET / HTTP/1.1 [note spaces] (which is not echoed to your screen, so be careful not to mistype it) you will receive a page of HTTP response data and HTML data. Thus proving that your port forwarding is working.
If you do not have any port forwarding set up at all, you can still test the loopback function by attempting to connect to port 161. This port is open on the BT routers and telnetting to it will result in a blank screen (as opposed to the attempting to connect message).
In summary: loopback works on the Home Hub 3B. Port forwarding also works to a degree but it is temperamental and does have some quirks, like not properly accepting ranges of ports. On this last point, at least, it would be helpful to get an acknowledgement from BT that this is a known fault.

Answer 1

There have been a number of threads discussing port forwarding and loopback, so I thought it might be useful to summarise my experiences. I have two HomeHub 3Bs on separate lines, one is a standard broadband line, the other is on an Infinity connection. My experience is limited to these two specific devices :-)
Port Forwarding does work but it is "temperamental" and "arcane" in the way you need to set it up. Although I have had it running perfectly, I have also had experiences where the router has refused to "accept" my changes. Tentatively, I put this down to the fact that I was running a Seagate GoFlex network drive on the network and this piece of equipment (definitely a Do Not Buy) was acting aggressively and screwing up the DDNS allocations. But ... YMMV
One definite probllem with Port Forwarding is if you attempt to specify a range of addresses. I have failed to get this to work on both my hubs. In my case I was trying to forward (say) 8021-8022 to 21-22, and the router insisted on forwarding both 8021 and 8022 to port 21.  The cure is to set up each port as a separate rule within the same user-defined application.
On Loopback, I know various people have said it doesnt work, but it has always worked fine for me, at both the locations where I have a HomeHub 3B. I use a DDNS service and I can test that my port forwarding is working by opening a Command Prompt window on my PC and typing  telnet mydomain.dyndns.web.com 21 or whatever. That command contacts my DDNS host to ascertain my IP address and then (attempts to) connect to port 21.
If port 21 is closed on your router (i.e. you have no port forwarding in place) you will see the message attempting to connect to mydomain.dyndns.web.com... and, after a while that will time out, with Could not open connection to the host, on port 21: Connect failed. If you do have your port forwarding set up correctly then your application will respond in some appropriate mannerr. However, you do need to understand what youre doing, because the response of an application that is expecting HTTP data is simply to do nothing!  You will probably get a blank screen. If you type GET / HTTP/1.1 [note spaces] (which is not echoed to your screen, so be careful not to mistype it) you will receive a page of HTTP response data and HTML data. Thus proving that your port forwarding is working.
If you do not have any port forwarding set up at all, you can still test the loopback function by attempting to connect to port 161. This port is open on the BT routers and telnetting to it will result in a blank screen (as opposed to the attempting to connect message).
In summary: loopback works on the Home Hub 3B. Port forwarding also works to a degree but it is temperamental and does have some quirks, like not properly accepting ranges of ports. On this last point, at least, it would be helpful to get an acknowledgement from BT that this is a known fault.