I need some help understanding the difference between IPv4 and IPv6 encrypted tunnels.
Today we create L2TP links between the routers and encrypt them with IPSec using IPv4 addresses to establish the L2TP links. Because we now have stable interfaces, we can use OSPF to route between our sites both for IPv4 and IPv6 traffic. This works pretty well except for the low MTU (1290). As more sites are getting dual stack IPv4 IPv6, I would like to switch over to using IPv6 addresses to establish the L2TP links.
My understanding is that the low MTU value we neet to set is due to the larger IPv6 headers. BUT, isn't IPv6 supposed to have IPSEC built in? How would I need to configure the router in order to encrypt the traffic passing through the tunnel when the tunnel is set up with an IPv6 link?