GRE is a simple IP packet encapsulation protocol. a GRE tunnel is used when packets need to be sent from one network to another, without being parsed or treated like IP packets by any intervening routers. a GRE tunnel interface comes up as soon as it is configured and it stays up as long as there is a valid tunnel source address or interface which is up.
L2TP is a tunneling protocol (used to support VPNs) that allows multiplexing of multiple PPP sessions between two IP-connected endpoints, and a control protocol for dynamically establishing and maintaining the emulation of these PPP sessions. This is very different than GRE.
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...