On my flatmates ObenBSD system with otherwise working tunnel setup (his sixxs tunnnel is working well) I'm not able to ping the inner tunnel endpoint and consequently neither through the existing tunnel. tunnel creation: # /usr/local/sbin/aiccu start Tunnel Information for T17002: POP Id : deham01 IPv6 Local : 2001:6f8:900:bc3::2/64 IPv6 Remote : 2001:6f8:900:bc3::1/64 Tunnel Type : ayiya Adminstate : enabled Userstate : enabled ping6 to inner endpoint: $ ping6 -c 3 2001:6f8:900:bc3::1 PING6(56=40+8+8 bytes) 2001:6f8:900:bc3::2 --> 2001:6f8:900:bc3::1 --- 2001:6f8:900:bc3::1 ping6 statistics --- 3 packets transmitted, 0 packets received, 100.0% packet loss tcpdump output: 19:53:04.199449 2001:6f8:900:bc3::2 > 2001:6f8:900:bc3::1: icmp6: echo request 0000: 6000 0000 0010 3a40 2001 06f8 0900 0bc3 `.....:@ ..ø...à 0010: 0000 0000 0000 0002 2001 06f8 0900 0bc3 ........ ..ø...à 0020: 0000 0000 0000 0001 8000 32f7 77f9 0000 ..........2÷wù.. 0030: 49b8 0890 0003 0afe I¸.....þ 19:53:05.207775 2001:6f8:900:bc3::2 > 2001:6f8:900:bc3::1: icmp6: echo request 0000: 6000 0000 0010 3a40 2001 06f8 0900 0bc3 `.....:@ ..ø...à 0010: 0000 0000 0000 0002 2001 06f8 0900 0bc3 ........ ..ø...à 0020: 0000 0000 0000 0001 8000 1278 77f9 0001 ...........xwù.. 0030: 49b8 0891 0003 2b7b I¸....+{ 19:53:06.207684 2001:6f8:900:bc3::2 > 2001:6f8:900:bc3::1: icmp6: echo request 0000: 6000 0000 0010 3a40 2001 06f8 0900 0bc3 `.....:@ ..ø...à 0010: 0000 0000 0000 0002 2001 06f8 0900 0bc3 ........ ..ø...à 0020: 0000 0000 0000 0001 8000 12c3 77f9 0002 ...........Ãwù.. 0030: 49b8 0892 0003 2b2e for good measure here the ipv6 portion of the route output: (i diffed the output against the working tunnel, and the only differt parts are the tunnel adresses) $ route -n show Internet6: Destination Gateway Flags Refs Use Mtu Prio Iface ::/104 ::1 UGRS 0 0 - 8 lo0 ::/96 ::1 UGRS 0 0 - 8 lo0 default 2001:6f8:900:bc3::1 UGS 0 0 - 8 tun0 ::1 ::1 UH 14 6 33160 4 lo0 ::127.0.0.0/104 ::1 UGRS 0 0 - 8 lo0 ::224.0.0.0/100 ::1 UGRS 0 0 - 8 lo0 ::255.0.0.0/104 ::1 UGRS 0 0 - 8 lo0 ::ffff:0.0.0.0/96 ::1 UGRS 0 0 - 8 lo0 2001:6f8:900:bc3::1 2001:6f8:900:bc3::2 UH 1 7 - 4 tun0 2001:6f8:900:bc3::2 link#5 UHL 1 12 - 4 lo0 2002::/24 ::1 UGRS 0 0 - 8 lo0 2002:7f00::/24 ::1 UGRS 0 0 - 8 lo0 2002:e000::/20 ::1 UGRS 0 0 - 8 lo0 2002:ff00::/24 ::1 UGRS 0 0 - 8 lo0 fe80::/10 ::1 UGRS 6 0 - 8 lo0 fe80::%nfe0/64 link#1 UC 0 0 - 4 nfe0 fe80::20f:eaff:fe65:fcc1%nfe0 00:0f:ea:65:fc:c1 UHL 0 0 - 4 lo0 fe80::%lo0/64 fe80::1%lo0 U 0 0 - 4 lo0 fe80::1%lo0 link#3 UHL 0 0 - 4 lo0 fe80::%tun0/64 fe80::20f:eaff:fe65:fcc1%tun0 U 0 0 - 4 tun0 fe80::20f:eaff:fe65:fcc1%tun0 link#5 UHL 0 0 - 4 lo0 fe80::4f8:900:bc3:2%tun0 link#5 UHL 0 0 - 4 lo0 fec0::/10 ::1 UGRS 0 0 - 8 lo0 ff01::/16 ::1 UGRS 0 0 - 8 lo0 ff01::%nfe0/32 link#1 UC 0 0 - 4 nfe0 ff01::%lo0/32 ::1 UC 0 0 - 4 lo0 ff01::%tun0/32 fe80::20f:eaff:fe65:fcc1%tun0 UC 0 0 - 4 tun0 ff02::/16 ::1 UGRS 3 0 - 8 lo0 ff02::%nfe0/32 link#1 UC 0 0 - 4 nfe0 ff02::%lo0/32 ::1 UC 0 0 - 4 lo0 ff02::%tun0/32 fe80::20f:eaff:fe65:fcc1%tun0 UC 0 0 - 4 tun0