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VPN between two sites with only one static IP?

Discussion in 'Cisco Small Business Routers and VPN Solutions' started by cable_guy, Mar 31, 2007.

  1. cable_guy

    cable_guy LI Guru Member


    I want to setup a hardware VPN between two sites. The issue I have is each ADSL site will have only one static IP offered by the ISP. Assuming that the first device connecting to the ADSL takes the static IP address, am I right in thinking I would need an all-in-one VPN Router with built-in modem? For example the Linksys RV042 or RV082 has all ethernet RJ45 ports and so couldn't dial the ADSL connection, so the connecting modem/router would adopt the single IP address?

    Is there another way to get a hardware VPN working with this setup, or is there a device that is a VPN Modem Router (and ideally wifi)? :confused:

    Any tips would be appreciated?

  2. d__l

    d__l Network Guru Member

    You don't need multiple static IPs for the devices behind the VPN routers. The ADSL modem will pass through the static IP to the router or simply be bridged and transparent to the router. Each router's WAN side has the public IP and the devices behind the router will have private IP subnets (each end of the tunnel with a different Class C subnet!).

    Once the tunnel is made, the two different subnets will be connected as one virtual subnet. Of course there are some tunnel configurations that can exclude portions of the subnets if desired to keep some devices "private" and non-shared from the devices on the other end of the tunnel.
  3. Toxic

    Toxic Administrator Staff Member

    you should also be able to use dyndns for the site that has no static IP.
  4. YeOldeStonecat

    YeOldeStonecat Network Guru Member

    Works just fine with a dynamic dns service. Matter of fact..you can have both ends on dynamic DNS...they'll find each other when one changes IPs.
  5. cable_guy

    cable_guy LI Guru Member

    Thanks guys, in fact both sites have the one static IP address each so there should be no need for dyndns. I wasn't sure if the DSL modem would adopt it though, so thanks for clearing that up.

    In which case is there a recommended Linksys DSL modem to use to bridge to the Linksys VPN routers. I have some experience with the RV082 and wanted to buy two to provide a stable VPN tunnel each side, but what are your thoughts on the RV042? I see the main difference are the number of ports and that the Rv082 supports a DMZ. Is the VPN technology as well implemented on the 42?

  6. d__l

    d__l Network Guru Member

    Which DSL ISP will you be using?

    Usually it is better to use the basic DSL modem that the ISP provides or sells with a static account. All the different ADSL modems are supposed to be completely plug compatable now, but some modem models will work better on certain DSLAMs. The ISP would provide modems tested for complete compatibility with their equipment and in the event of DSL sync problems, the ISP-provided modem should be fully supported.

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