I am creating a point to point link between one cetral site and one remote site utilizing ISDN until my organization can procure a dedicated leased line (E1). Now the planning requires putting 4BRI lines as a bundle (to use aggregate bandwidth of 512Kbps) for this primary link (4 bri's at the central site, and 4 at the remote site. I require the link to only come up when interesting traffic triggers the ISDN Line (we will have a VTC/V OsIP requirement max 2 hours per call). The equipment at the central site is 1 2811 (RED) router connected to a KG-250 IP encryptor then to another 2811 (Black) router and the same is true for the remote site with the ISDN link between the two "Black" routers. I am using a GRE tunnel on the "Red" side. I need a solution to keep the GRE tunnel and encryptors from passing fake "interesting" traffic which in turn prematurely activate the ISDN lines. My problem is of course allowing VOIP/VTC traffic on the "Red" side for my Dial-on-Demand routing. Suggestions???