There is a discrepency on the MTU on the ipv6 protocol and MTU on the tunnel transport. Is this correct? Also, please feel free to suggest changes to my config. It seems to work perfectly:) ipv6gw#sh ipv6 interface tunnel 1 Tunnel1 is up, line protocol is up IPv6 is enabled, link-local address is FE80::2 No Virtual link-local address(es): Description: IPv6 tunnel to SixXS Global unicast address(es): 2001:16D8:?:?::2, subnet is 2001:?:?:?::/64 Joined group address(es): FF02::1 FF02::2 FF02::1:FF00:2 MTU is 1280 bytes ICMP error messages limited to one every 100 milliseconds ICMP redirects are enabled ICMP unreachables are sent Output features: CCE Classification Zone based Firewall ND DAD is enabled, number of DAD attempts: 1 ND reachable time is 30000 milliseconds (using 30000) ND RAs are suppressed (periodic) Hosts use stateless autoconfig for addresses. ipv6gw#sh interfaces tunnel 1 Tunnel1 is up, line protocol is up Hardware is Tunnel Description: IPv6 tunnel to SixXS MTU 17920 bytes, BW 100 Kbit/sec, DLY 50000 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation TUNNEL, loopback not set Keepalive not set Tunnel source 84.?.?.?, destination 83.140.3.18 Tunnel protocol/transport IPv6/IP Tunnel TTL 255 Tunnel transport MTU 1480 bytes Tunnel transmit bandwidth 8000 (kbps) Tunnel receive bandwidth 8000 (kbps) Last input 00:00:41, output 00:00:41, output hang never Last clearing of "show interface" counters never Input queue: 0/75/89/0 (size/max/drops/flushes); Total output drops: 0 Queueing strategy: fifo Output queue: 0/0 (size/max) 5 minute input rate 0 bits/sec, 0 packets/sec 5 minute output rate 0 bits/sec, 0 packets/sec 1084605 packets input, 1137330974 bytes, 0 no buffer Received 0 broadcasts (0 IP multicasts)