For 6500 with Sup720:
HW support
Currently, Cat6k Sup720 supports GRE & IPIP mode of tunneling in HW. Tunnel tos & Tunnel ttl options are also supported in HW.
SW support
Certain tunnel features, such as tunnel checksum, tunnel path-mtu-discovery,
tunnel sequence-datagrams, tunnel flow egress-records, tunnel key when applied
on the interface, are supported in software. For features requiring software
processing, we create a 'punt' adjacency in HW, to punt the packet to the software
path. Tunnel mode nos is supported in software. Also, IPX & Appletalk & Multicast & NAT tunneling are supported in software. Packets requiring fragmentation (where input interface mtu > tunnel ip mtu) are sent to software for fragmentation.
