IPv6 with Cisco devices
A typical interface configuration on a Cisco router
interface Ethernet1/0 ip address 10.125.117.1 255.255.255.0 ipv6 address 2001:db8:21F0:117::1/64 ipv6 address 2001:db8:21F0:117::/64 eui-64 ipv6 enable ipv6 nd prefix 2001:db8:21F0:117::/64 ipv6 nd managed-config-flag ipv6 nd other-config-flag !
If the DHCP server is on a different network segment than the client one has to add to following 2 lines for IPv4 and IPv6
ip helper-address 10.125.116.2 ipv6 dhcp relay destination 2001:db8:21F0:116::2 Ethernet1/7