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VPN over ADSL

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VPN over ADSL

Hi,

I have two offices, each with NO NAT ADSL. I want to connect them using VPN. The firewalls I am using have VPN capabilities. I have two DLink DSL-500 Modem routers but I cannot get them to work as I need.

If I take one office as an example.

IP Address Range: 212.159.64.212 - 212.159.64.215
Subnet Mask: 255.255.255.252
Giving 2 Useable IP Addreses: 212.159.64.213 is assigned to the Modem/Router

I want to assign 212.159.64.214 to the firewall, which in turn routes to my mail server and the rest of the network if I open the ports.

How do I get the DLink modem/router to allow me to assign 212.159.64.213 on the ethernet address side when this is the address assigned to the Modem side. If I try it I get an error "WAN IP and LAN IP must be on different subnets". There is an option to set it up as a Bridge with RFC 1483 and Router with RFC 1483 Bridged Encap., but what do these mean.

I have the latest UK firmware installed and the manuals and DLink website don't seem to have caught up with it yet.

Anyone done anything like this? Any help much appreciated.

Steve C
4 REPLIES
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RE: VPN over ADSL

This will not work. The router needs one IP all for itself. If you ahve a second IP assigned to a firewall, you have no more available IPs for VPN, unless the firewall is a PC running the VPN client.

Kind Regards

Kevin

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RE: VPN over ADSL

Hi Kevin,

The Firewall is Smoothwall Corporate Edition (linux), which has VPN built in. It is simple to set up a VPN connection between two private networks. You don't even need PPTP enabled on the Network servers.

The problem I am having is with the DLink modem/router. I need it to have the 212.159.64.213 presented on the ethernet port so that I can give Smoothwall's Red NIC the 212.159.64.214 IP. Smoothwall's Green NIC faces my private network (192.168.xxx.yyy), but it doesn't seem to like this. I have an old BT ADSL modem which did this no problem, but I cannot figure out how to change the IP address. When I use this to connect it seems to retain it's old IP (213.2.30.1).

Should I be using just an ADSL modem, without the router bit. These seem difficult to obtain, except in USB or PCI internal cards. Can you reccomend any?

Regards

Steve C
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RE: VPN over ADSL

Quote
How do I get the DLink modem/router to allow me to assign 212.159.64.213 on the ethernet address side when this is the address assigned to the Modem side. If I try it I get an error "WAN IP and LAN IP must be on different subnets.


I'm a bit surprised at this. The WAN side of the link is a PPP connection, and I thought it is legitimate for a PPP interface and an Ethernet interface in the same device to both be given the same IP address. (Source: "Using & Managing PPP" by Andrew Sun, O'Reilly, Ch.8 ""Network Architectures Incorporating PPP", p.19Cool.

This is exactly how Force9 suggests in its Networking with ADSL page for No-NAT; and they show how to do this for the D-Link DSL-504 a few pages later --
http://www.plus.net/supportpages.html?a=218.

Edited on 2003-08-27 to bring up to date for phpBB and added the references to the Force9 support pages. (Also corrected my horrible spelling of "source" as "sourse" Shockedops: )
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RE: VPN over ADSL

> > How do I get the DLink modem/router to allow me to assign 212.159.64.213 on the ethernet address side when this is the address assigned to the Modem side. If I try it I get an error "WAN IP and LAN IP must be on different subnets".
>
> I'm a bit surprised at this. The WAN side of the link is a PPP connection, and I thought it is legitimate for a PPP interface and an Ethernet interface in the same device to both be given the same IP address. (Sourse: "Using & Managing PPP" by Andrew Sun, O'Reilly, Ch.8 ""Network Architectures Incorporating PPP", p.19Cool.

Hi Stephen

That's what I thought should happen.

I'll have another go, to see if I can get it working. If not I may try DLink again, or switch to Eicon Modems.

Thanks

Steve C