I am working on a design to use VPN to backup a frame relay network. I am using GRE tunnels to pass the traffic back and forth when the frame relay network is unavailable, using the "Backup Interface" command on the frame-relay sub interface.
This keeps the tunnel down until the frame network DLCI is down correctly. An idea came to mind though, is there a way to keep my tunnel interface down based on a lack of a route in the table? This would be similiar to the ISDN dialer-watch command, which looks for the presence (or lack of) a route, before bringing up the dialer. I'd like to apply the same theory to the VPN tunnel interface. This gives me a solution that prevents any potential telco related black holes, in the event that an interface stays up when it shouldn't.
There might be something about your environment that I do not understand well which would impact this. But it seems to me that if there is no "interesting" traffic going through the GRE tunnel then the VPN will not become active. So if you configure floating static routes (instead of backup interface) as long as the Frame Relay is active its routes would be in the routing table and only if the Frame Relay fails would the floating static be put into the routing table which would trigger the VPN to come up. As long as the floating static route is not in the table then the VPN will not come up.
I am not clear why you care about keeping the VPN down. With normal dial backup we are motivated to keep the dial inactive because we pay based on the amount of activity. But with VPN we usually pay for the connection not for the amount of activity. Perhaps you can clarify why you want your design to work in this way.
Table of ContentsIntroductionVersion HistoryPossible Future
UpdatesDocuments PurposeNAT Operation in ASA 8.3+ SectionsRule Types
Network Object NATTwice NAT / Manual NATRule Types used per SectionNAT
Types used with Twice NAT / Manual NAT and Network Obje...
Table of Contents Introduction:This document describes details on how
NAT-T works. Background: ESP encrypts all critical information,
encapsulating the entire inner TCP/UDP datagram within an ESP header.
ESP is an IP protocol in the same sense that TCP an...