My ISP assigned prefix is: 2607:F4B8:3::/48 So I am building my internal IPv6 firewall/router/ etc. I want to have a static IPv6 address on its eth0 so that I can create static v6 routes to it from the gateway. I add the following lines to ifcfg-eth0: HWADDR=00:40:F4:05:A8:F1 IPV6INIT=yes IPV6_AUTOCONF=no IPV6ADDR="2607:F4B8:3:1" if-up eth0 gets the error: Error: an inet prefix is expected rather than "2607:F4B8:3:1/64". ERROR : [ipv6_add_addr_on_device] Cannot add IPv6 address '2607:F4B8:3:1/64' on dev 'eth0' What is missing? Why is it not building an address of 2607:F4B8:3:1:0:40:F405:A8F1 ? I am reading: file:///usr/share/doc/initscripts-8.45.19.EL/sysconfig.txt for my 'inspiration'. Other sources are welcome... OH, /etc/sysconfig/network does have the line: NETWORKING_IPV6=yes