VPN disconnect

This is another VPN question.

We have a regular IP address which we use to connect to a PPTP VPN which assigns us 10.0.1.29. If the PPTP connection goes down, we will lose that address.

Our software relies on our IP address being 10.0.1.29. Is there a way, if the VPN temporarily goes down, to maintain the IP address of 10.0.1.29 ?

You can tell pppd to request a particular address by adding it to your options, like this:

	pppd 10.0.1.29: ipcp-accept-local

(The ":" at the end means "request this local address, and don't insist on any particular peer address.")

pppd doesn't have an automatic means to save the last-used address for a link and pick it up again. Perhaps it should have one, but you could do this in a script by having your own /etc/ppp/ip-up that stores $IPREMOTE into a file, and then pull in that file's contents for a later invocation of pppd.

Note that this just tells pppd to request a particular address. There's no telling whether the peer understands what to do with such a request, or if it can or will honor it. Some servers may refuse to negotiate at all under such conditions, causing the link to fail. (Bugs are unfortunately common.)

James Carlson         42.703N 71.076W         <[email protected]>

On the peer side, pptpd on Linux in the default configuration gives the IP address to pppd on command line, and so the IP address is usually non-negotiable. I don't know about other peers.

James Cameron                         http://quozl.netrek.org/
HP Open Source, Volunteer             http://opensource.hp.com/
PPTP Client Project, Release Engineer http://pptpclient.sourceforge.net/