> I use them for my network. RFC5969. aha! do you mean 5. Troubleshooting and Traceability ... The 6rd CE and BR SHOULD support the IPv6 Subnet-Router anycast address [RFC4291] for its own 6rd delegated prefix. This allows, for example, IPv6 ICMP echo messages to be sent to the 6rd virtual interface itself for additional troubleshooting of the internal operation of 6rd at a given CE or BR. randy