Topic: SME Gateway - ADSL2+ Half bridge modem

[arne]

Hello !

For a while I have been working with a Billion Bipac 5102S ADSL2 router to reconfigure it to run PPPoA under Annex_B (ADSL over ISDN) and bridge mode.

After some discussion with Billion support I received an firmware that should be able to make what they call a "half bridge".

To make a rather long story short, I now run a SME 7.0 gateway with a "half bridge" in front, and in some strange way it works.

I really do not understand completely what this "half bridge" really is. First at logon the SME gateway only receives a local ip from the Billion box. (192.168.1.100) After a number of reeboots of the Billion box and the SME gateway then the local ip that the SME gateway had received from the Billion box suddenly were replaced with an external ip.

It works now, but it is my impression that if I should power down my quipment, I would have to make a series of reboots (??!!) to make this stange "half bridge" to start working again (??!!).

Is there any of you who know more abouth this "half bridge" solution, or how to make it work bether ?

If I could make it work copleteley and reliable, I think I could have the external ip and the full ADSL+ speed into the SME gateway.. (At the moment I only pay for standard ADSL as my old Netopia bridge modem can do only standard ADSL speed. If the Billion box can work reliabile in ADSL2 Annex_B and bridge mode I will upgrade.)

I think there is some other brands as well, exept for Billion, that use this "half bridge priciple" ..

Best reg Arne

[arne]

To ask the same question in a little bit different way:

From searching the internet a little bit and from my own experiments it looks likt this "half bridge mechanism" has something to do with the dhcp client of the sme server and how this work.

If the ADSL2 modem working in "half bridge mode" is considered to be a "black box", it looks like the first time it is requsted for an ip by the sme server, the SME server dhcp client it will receive an internal ip. (In my case 192.168.1.100).

Then, it looks like, later on, when it is asked again by the SME dhcp client, it will for some reason deliver the external ip to the SME gateway and the internet connection will work.

Is there some way to make the dhcp client of the SME server to ask about the IP adress, one time more, or in some way "different", so it will more easily obtain the external IP that the ADSL2 modem will give, it if it's just asked "deep and well enough" .. ??

[arne]

Something here ?
http://www25.nortelnetworks.com/library/tpubs/pdf/router/soft1300/03513A00.PDF

[SARK devs]

Hello Arne,

We commonly run "half-bridge" mode  for our customers (PPPoA over ADSL/ADSL2) and we also use the 5102, although I believe the device is now obsolete or obsolescent.   Restart is not an issue and is totally automatic.  SME server runs in server-gateway mode and the  IP it receives fom the modem (from DHCP) is the true external IP address so it looks to a casual observer as if the 5102 doesn't exist.  

The 5102 is a little quirky to set up in half bridge but not difficult once you know it.  Here are the steps.

1  Connect the modem to the ADSL filter and to your network switch in the normal way. Initially I think the factory default for the modem is 192.168.1.1.

2. Log on to the modem and use the quickstart wizard to fill out your ADSL radius details.

3. In the advanced setup turn half-bridge mode on and turn NAT off. This will be automatically reported in the modem as a DHCP pool of 1 member with an address range which is the external wan address of the modem. Save your changes.

4. Disconnect the modem from your network switch and connect it to the WAN ethernet socket of your SME Server.

5. Set yor SME Server to server-gateway mode and to receive an IP address from the modem via DHCP.

6. Connect your netwotk switch to the LAN ethernet socket of your SME Server.

7. Restart SME Server.

That's it. you are done.  If you now log on to your SME Server and issue an ifconfig you will see that eth1 has your true external IP Address.  It's as if the modem doesn't exist; it runs completely transparently.  

I have never traced the DHCP process between SME and the router but I was not aware of any "two-stage" process such as the one you describe.  We simply observe SME Server coming up with the external IP address.  It makes for very easy and convenient running in server-gateway mode and uses only a single external IP address.

Kind Regards

Selintra

[arne]

Thanks a lot for your info. I will try to go trough it all once more.

About the half bridge .. After the SME server has received the external IP and the Billion box is made "transparent" I am actually still able to go into the Billion modem from the lan using this address: http://192.168.1.254

From here it is posible to log into the modem as if it was running in routing mode, even though it deliver in the external adress to the SME server.

It works like a bridge with an internal IP connected to it.

The bridge has the IP 192.168.1.254, the external card of the SME box has the external address. The internal card of the SME box has the ip 10.0.0.1 Still it is possible to type this adress in a web server at lan to go into the Billion bridge/modem: http://192.168.1.254 (So that the logon should not be admin/admin.)

The bridge ip can of cource also be pinged.

It could be things are working slightely different here.

As the Billion Box is delivered here it can do "half bridge" as standard while comunicating against an analog telephone line. If it is a ISDN line and a standard firmware, the "half bridge" option does not exist. It is removed. To make it work with PPPoA against an ISDN line I had to install another firmware, that Billion claimed is still Beta. It could be things are working slightely different here because of this beta software (??)

By the way .. yes you are right it is no a outgoing product, but it was the latest and newest modell when I started up to make my configuration (And hopefully in the end now, it's working.)

Arne

[arne]

Today I wanted to make a test for a complete shutdown and power down for the SME server gateway and the Billion modem, to see how they would boot up again.

surprice, surprice .. this time it just booted up and the SME gateway just received the external IP without a problem.

I can see from the log (/var/log/messages) that yesterday when I made the first setup the dhcp client of the sme gateway made houndreds of request to the Billion modem before it got the right and proper external IP. Today I think it received it on first attempt.

In some way the Billion box is transparant in that way it does not have en external IP, and in some way it is not as it is also comunicating against the sme server as ip 192.164.1.254

I don't understand it completely, but here is a sequens from the log during startup today:

Dec  5 16:33:05 s7 dhclient: DHCPOFFER from 192.168.1.254
Dec  5 16:33:05 s7 dhclient: DHCPREQUEST on eth1 to 255.255.255.255 port 67
Dec  5 16:33:05 s7 atalk: Starting AppleTalk services:
Dec  5 16:33:05 s7 atalk: (backgrounded)
Dec  5 16:33:05 s7 atalk:
Dec  5 16:33:05 s7 dhclient: DHCPACK from 192.168.1.254
Dec  5 16:33:05 s7 rc.e-smith: Starting atalk:  succeeded
Dec  5 16:33:05 s7 atalkd[3315]: restart (2.0.3)
Dec  5 16:33:05 s7 smb: Starting nmbd:
Dec  5 16:33:05 s7 nmbd: Starting nmbd succeeded
Dec  5 16:33:05 s7 smb: 
Dec  5 16:33:05 s7 smb:
Dec  5 16:33:05 s7 smb: Starting smbd:
Dec  5 16:33:05 s7 smbd: Starting smbd succeeded
Dec  5 16:33:05 s7 smb: 
Dec  5 16:33:06 s7 smb:
Dec  5 16:33:06 s7 rc.e-smith: Starting smb:  succeeded
Dec  5 16:33:06 s7 atalkd[3315]: zip_getnetinfo for eth0
Dec  5 16:33:06 s7 messagebus: Starting system message bus:
Dec  5 16:33:07 s7 esmith::event[3314]: Processing event: ip-change 80.202.198.114
Dec  5 16:33:07 s7 esmith::event[3314]: Running event handler: /etc/e-smith/events/actions/generic_template_expand
Dec  5 16:33:07 s7 messagebus: messagebus startup succeeded

If I gi into ip 192.168.1.254 with a web browser from LAN I can still log into it.

My last router modem the Netopia 3351 vere just invisible when I reconfigured it to be a bridge. The Billion "half bridge" is still available for configuration and maintenace from its local IP.

All in all it loks like everything now works OK and that I did not get all those problems that I expected after trying to boot up the system the first time.

One more time thanks for the help.

Arne.