Help with ADSL router and my network, please

[Woz]

Right. I currently have a pants WDSL connection that is as reliable as Chinese imports. It is currently plugged into a 4 port Netgear firewall/router. It works absolutely fine and, apart from the poxy WDSL has never fallen over in 5 years (oh crap I wish I hadnt said that).

Now I have ADSL set up on a phone line and if I connect directly to the Voyager 205 router using ethernet then it works fine so no problems with the ADSL connection.

Ideally what I would like to do is simply plug the Voyager modem straight into my existing router, replacing the WDSL one so then I'll have the minimum of fuss and fiddle swapping over. However- when I do this and set up my Netgear jobbie with the appropriate ADSL IP settings nowt happens.

Just to complicate things I have an SBS 2003 box on the network that hijaks all the services it can like DHCP and DNS. I don't really want to run the ADSL connection into the back of this, though.

Any hints?

[Keiron]

Have you cloned over the MAC address, not sure if your ISP requires this but a lot do.

Is it worth dumping the kit and buying something else? Thinking about it you are going from the Voyager 250 (2 ports) to Netgear Firewall/Router (4 ports). All that port routing is going to be a pain?

[John Touhig]

Originally Posted by Keiron

Have you cloned over the MAC address, not sure if your ISP requires this but a lot do.

Most ISP's grab the MAC address of the device thats attached to the xDSL when you go through set up. So you will probably need to get your router to spoof the new MAC address.

[Woz]

Kieron it's not really a 2 port only a 1 port with another USB connection which I am not going to touch with a barge pole. All I want the 205 to do is simply act as a modem rather then do the whole NAT / DHCP malarkey and leave the NAT and other thingummies to the Netgear box. The 205 is still directly connected to the ADSL service so the ISP should pick up its MAC address anyway.

[MattS]

First off the the BT voyager 205 is known to have issues when connected to a hub or switch. I have a customer with a similar problem which I am due to look at in the next day or so. As an alternative to the Voyager I use these things;
http://www.refreshcomputers.com/defa...uct&txtid=5309
It is based on a bog standard Connexant ASR400 chipset and does pretty much anything you might want at the cost of not being totally user friendly.

Once you manage to get traffic onto Ethernet you need to think about the NAT implication. Your WDSL router, is more than likely a bridge, rather than a router. All ADSL modems used in the UK are actually routers and thanks to BTs IPoA implementation they don't like bridging or half bridging. So you need to set up a legitimate route from the public address space to your private LAN address space.

There are various ways to do this. The only method that I don't charge good money to provide is double NAT.

For instance, assuming your internal LAN is on 192.168.1.0. Physically connect the Modems LAN interface to the Firewall's WAN interface (you may need a crossover cable). Keep it simple and avoid patching through a hub/switch.
Modem WAN interface - some public IP
Modem LAN interface - 10.0.0.2
Firewall WAN interface - 10.0.0.1
Firewall LAN interface - 192.168.1.2

The common mistake is to put the Modem LAN interface and the Firewall WAN interface on the same subnet as the Firewall LAN interface. Nothing flows as routers only forward between different subnets.

The basic rule with SBS is to put everything on the SBS server. DNS, DHCP, WINS etc. This will mean turning off the DHCP server on the Firewall (only one DHCP server per segment). If there is a DHCP server on the modem turn that off as well although in theory it should not cause any trouble.

I guess you are not using ISA server?

[Woz]

Aha. Right- will give it a go. I may be some time. Send roast potatoes.

Right. A quiz for you on the firewall and modem settings:

Firewall:
WAN router address 10.0.0.2
Firewall NAT public address 10.0.0.1
WAN subnet mask 255.255.255.0

Voyager 205:
WAN address: public IP assigned by ISP
LAN address: 10.0.0.2

I'll give it a shot.... will I be able to browse the settings/Telnet into the modem at 10.0.0.2?

[Woz]

Update:
tried that and no joy with the settings above. However- the modem for some reason whenever I change its IP address then fails to connect to anything- I can't ping it. Even if I change it from the default 192.168.1.1 to 192.168.1.2 which should not really make a difference.

If it's any use I have a block of static IP addresses so can use one for the modem and another for the router. I just need the modem to talk to the WAN port on the router without sulking.

So- how about I set up the modem with one IP with NAT disabled then set up my firewall to use the other IP with NAT enabled for the rest of the connected network? Then all I have to do is get the modem to talk to the WAN port on the firewall. Somehow. With a mallet possibly.

[StuartC]

in theory you ought to be able to assign your IP addresses to each device.
Set your PCs to use the router as their default gateway, and the router to route external traffic outside your IP subnet to the ADSL modem, which will then communicate with the external big bad web.

in theory at least....

[Woz]

Yes, in theory. However in practice it appears the 205 is a bag of kak and should be used only for warming your pies at lunchtime. However- I will persist for a bit then throw a wobbly and stamp on the smug little green lighted git.

[Woz]

What I'm trying to do is essentially the same as using an external ethernet connected ADSL modem with a wireless router. Same problem. So I can't be the only person wrestling with it.