I got 2 things a tunnel: SixXS IPv6 : 2001:xxxx:yyyy:7d4::1/64 Your IPv6 : 2001:xxxx:yyyy:7d4::2/64 and a subnet Prefix : 2001:xxxx:yyyy:87d4::/64 the SixXS whois shows this: This route goes to an endpoint of xxxx-SIXXS This route is routed to 2001:xxxx:yyyy:7d4::2 Via ayiya tunnel to my IPv4-address the tunnel itself works perfekt; Here in the FAQs How do I give connectivity to other hosts on my subnet? this subnet is called the "Default subnet"; my thoughts: one linux box has the aiccu service running for the tunnel; the eth0 device has e.g. 2001:xxxx:yyyy:87d4::1/64 as IPv6-address and another linux box has 2001:xxxx:yyyy:87d4::2/64 as IPv6-address; both linux boxes ping each other; the one linux box that runs the aiccu service allows e.g. ping6 ipv6.google.com but the other shows this when doing the same: From 2001:xxxx:yyyy:7d4::1 icmp_seq=# Destination unreachable: Administratively prohibited why this? the same when the one linux box with the running aiccu service has also running radvd and the other gets its IPv6-address automatically; can someone please explain, what I did wrong ..., or why this doesn't work ... Thanks, Walter