DHCP and static IP in the same time. Is it possible?

Discussion in 'Cisco Small Business Routers and VPN Solutions' started by Sfor, Nov 26, 2007.

  1. Sfor

    Sfor Network Guru Member

    I do have 3 Linksys routers connected through Airbites WAN. Two WRV200 and one RV042. They all make one IPSec VPN network.

    The WAN IP is obtained by DHCP according to the MAC. Or rather, it should be done that way. If the static IP is forced, the Airbites Internet gateway server redirects HTTP queries to other servers demanding autentication every few hours. On the other hand the VPN goes down, when the DHCP server (in the Airbites gateway server) goes down. The DHCP lease time is 18 hours, but the WRV200 routers are rebooting themselves quite often. If the Airbites server goes down, so is the VPN, as the router is not getting the proper IP after a reboot, then. Static IP makes the VPN much more reliable, but it results in the problematic HTTP traffic redirections.

    I was unable to persuade the Airbites workers their authentication system does not work correctly. They are always saying to turn the DHCP on, instead of tweaking their servers.

    The work around would be to turn the DHCP for a moment, just to make a proper entry in the server database, then to switch to static IP, again. Or perhaps to make the DHCP IP renew routine from some other network device without touching the router config. The problem is, the MAC address has to match the router MAC during the DHCP renewal procedure. Still, there should not be two devices with the same MAC connected to the same network. So, the other device with the same MAC should be connected just for the time necesary to renew the IP address.

    I'm looking for other ideas, but the additional device just to trigger the DHCP autentication mechanism seems to be relatively simple to do. Still, I do not know how to do it.

    Well, I was experimenting with connecting two devices with the same MAC to the same switch. It seems to be working, but there are communication problems as well, I think. Perhaps, if I would use an ethernet hub instead of a switch the result would be better.
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