Unpredictable connect to broadband - IP address problem? Or...?

[#1]

@itsme
No, you are not out of your depth, no-one always gets things right, but in this case I believe you are wrong. If you read the manual for this (horrible IMHO) device and look at the stats provided something is amiss, so going through methodically checking everything is the only sensible option. Softmuse may not have responded yet for several reasons, there was a couple of days delay in his responses at the start of this thread, and several weeks spread on another of his threads on his problems. I suggest we leave this thread alone until he has had time to pick his way through it and come back, if indeed he's still got a problem.
Regards.

[#2]

As I do use an Ethernet Modem and I can't see anything amiss with the stats please let me know what you find amiss? Also bear in mind that these stats are when the OP has the system working. If you believe it's the Public IP address being passed to the LAN and  you believe that the LAN should have a private IP can I ask how this can be achieved without a NAT?
Also I need to correct an early recommendation/suggestion to buy a 5-port switch. Don't as the modem has no router and the switch will not work. The DSL-320B can either be connected to a single PC or a router if multiple PC and needed to be connected.

[#3]

Quote from: itsme

Also I need to correct an early recommendation/suggestion to buy a 5-port switch.

That might have been me. RTFM
The D-Link site says:
"The DSL-320B ADSL2+ Ethernet Modem is a high-speed broadband modem which connects to any computer with an available Ethernet port, or to a broadband router to share high-speed Internet access with a group of users at the office."
OK, so maybe £15 rather than £5 for a cheap one. 

[#4]

It seem that Plusnet and others don't know how Ethernet modems work reading this

Quote

I've just had broadband activated and the ISP (Force9, ie. PlusNet) sent me a D-Link DSL-320B router. I'm on Edgy Eft Ubuntu and I think it's a RealTek network interface. The router uses DHCP and supplies a local IP address to my network card (eg. 192.168.1.3), all fine. (I'm checking this through System / Admin / Network Tools.) Then I attach the router to the ADSL line and it clearly connects to the ISP - the router's DSL light comes on and its status page shows that it has picked up an external IP address from the ISP, along with DNS servers. As soon as that happens, my network card acquires the same network address as the router just picked up - 87.something. I can no longer even connect to the router at that point, and have to put the PC on a static 192. address to do so. I can't get to any web pages. I've tried with and without static address and DHCP, and also twiddled the DNS entries (System / Admin / Networking) and the proxy info in Firefox, to no effect. I spoke to the ISP and they reckoned the router should not be providing the external address to my network card, so they sent me a new router - which does exactly the same. I'm going to try a Windows laptop tonight to see if it works for Windows. Ideas welcomed, bearing in mind that I know next to nothing about Ubuntu/Linux at the command line

I believe the latest firmware for the DSL-320B was to get over the problem of losing the modem control panel when connected to the internet.

[#5]

Interesting, D-Link describe the DSL-320B as a modem.
What have PlusNet been describing it as?
All current products now have a "free 4-port router" according to the web site.
Maybe this neeeds to go to a new thread, to avoid digressing too far from the OP's original problem?

[#6]

I think I can see now why this D-Link DSL320B is such a fiddly device to work with.  What you get may depend on what sequence you connect or switch things on.
In its default configuration (and after you have used its Wizard setup as described in Plusnet's webhelp) it is set up in "Half-bridged" mode whereby it will sync with the exchange and handle authentication of your session with Plusnet.  But from thereon it passes (almost) all traffic to the local LAN port including the assigned WAN IP address and gateway which is then adopted by the local network card (.. or independent router if substituted).  When your network card has acquired a WAN address from Plusnet (87.x.x.x in the previous examples), by rights you shouldn't be able to talk to your D-Link modem anymore as 192.168.x.x is defined by international standards as a private-network non-routable address and when your browser passes any such addressed packets to the Plusnet gateway it will just drop it rather than passing it back to the D-Link modem.  This should certainly be the case in Full Bridged mode.
However the D-Link has to provide a way to access its configuration pages and this is why I guess it is set up to act as a DHCP server, so that if you plug into it with your network card (without the D-Link being connected to the telephone line) it will give you an IP address in the 192.168.1.x  range so you can talk to it.
However, now comes the interesting question, if your network card has been assigned (as usually) a 3 day lease of an 192.168.1.x  address by the modem, what is going to happen when you now plug the modem into the telephone line to connect to Plusnet?  Will the network card and Plusnet remain in different universes (IP address speaking) until you explicitly release the previous IP address -- or reboot the computer?  Especially as, apparently, the D-Link doesn't do Network Address Translation.
Curiously, Softmuse was still able to access his modem stats at (presumably) 192.168.1.1  when he was connected -- which is not standard rules or behaviour when your originating device has an address of 87.112.x.x  (ie to all intents and purposes you are part of the great internet.)  Hence why I said "(almost) all traffic" in the 2nd paragraph.
I think my suggestion to Softmuse would be to, (1)switch on computer, (2)switch on modem and plug it into the phone line, (3)when lights show DSL connection -- plug computer into the modem.  If it doesn't work, do an explicit "IPconfig /renew" or "Network Connection Repair" as described earlier in this thread.  It could of course also be that his (or all) D-Link modems are flaky at doing the session authentication with Plusnet.
All in all, seems easier to buy a new combined modem-router, with NAT & robust firewall.

[#7]

You have got it right except with the Ethernet modem that I have if I use the PPPoA bridging which I'm not sure is half bridging then the DHCP supply the gateway address as the public IP plus 1. As the gateway is via the modem then the control panal can be accessed using the private IP.
I have used my modem in full bridge mode probably with the DHCP disabled and the router get the PN IP and gateway and I can't access the modem control panel.

[#8]

Anyone out there with a real 320B who knows what they're doing that can give a full and correct answer to the OP? 
(if not, as I'll be passing, I might call in this morning on the person whose 320B I set up very recently and have a  quick look)

[#9]

Did you have a quick look? For completeness of this thread it would be great if it can be confirmed what IP address is passed to the LAN.

[#10]

Quote from: itsme

Did you have a quick look?

They were out and I haven't been near since.

[#11]

Dont over look your anti-virus program could cause problems with connecting too.
I find windows anti-virus and my virus program (panda global 2009) fight each other until panda pop up a message asking which to make a default.  Some virus programs dont always display the message and with ms vista you need to turn its firewall off then exceptions off  and then take the tick out of the box for your lan card and or wireless.
I find since I have had a static ip address its a lot easier but their are times when I cannot connect but a re-boot  often helps.
puddy