Because you need to use GRE to create a virtual interface on the router and thus enable the use of routing protocols. At least, that's the only way I know how to do it. C. -----Original Message----- From: Iljitsch van Beijnum [mailto:iljitsch@muada.com] Sent: Monday, February 17, 2003 6:19 PM To: Steve Feldman Cc: nanog@nanog.org Subject: Re: VoIP over IPsec On Mon, 17 Feb 2003, Steve Feldman wrote:

through the corporate enterprise net, Cisco routers with IPSEC/GRE tunnels over the public Internet.

Maybe a stupid question... why would you need GRE tunneling while IPsec has a tunnel mode of its own?