UNIX for Advanced & Expert Users

Hi
I am trying to setup a very basic dhcp dual stack configuration, so I have 2 dhcpd.conf file dhcpd4.conf and dhcpd6.conf
# cat /usr/local/etc/dhcpd4.conf
Subnet 10.45.192.0 netmask 255.255.248.0 {
option subnet-mask 255.255.248.0;
option routers 10.45.192.1;
}# cat /usr/local/etc/dhcpd6.conf
option dhcp6.name-servers 2001:1b70:82a1:a:0:4000:2:1;
option dhcp6.domain-search "sken.com";

subnet6 2001:1b70:82a1:a/64 {
range6 2001:1b70:82a1:a:0:4000:2:1 2001:1b70:82a1:a:0:4000:10:1;
}

however when I try to run the second instance of the dhcp server with the /usr/local/sbin/dhcpd -6 -q -lf /var/lib/dhcp/dhcpd.leases -cf /usr/local/etc/dhcpd6.conf I get the following in the messages file

/usr/local/etc/dhcpd6.conf line 4: Invalid IPv6 address.
subnet6 2001:1b70:82a1:a/

ifconfig for server is

# ifconfig -a
lo0: flags=2001000849<UP,LOOPBACK,RUNNING,MULTICAST,IPv4,VIRTUAL> mtu 8232 index 1
inet 127.0.0.1 netmask ff000000
e1000g0: flags=1000843<UP,BROADCAST,RUNNING,MULTICAST,IPv4> mtu 1500 index 2
inet 10.45.192.4 netmask fffff800 broadcast 10.45.199.255
ether 0:c:29:4a:f9:4b
lo0: flags=2002000849<UP,LOOPBACK,RUNNING,MULTICAST,IPv6,VIRTUAL> mtu 8252 index 1
inet6 ::1/128
e1000g0: flags=2000841<UP,RUNNING,MULTICAST,IPv6> mtu 1500 index 2
inet6 fe80::20c:29ff:fe4a:f94b/10
ether 0:c:29:4a:f9:4b
e1000g0:1: flags=2000841<UP,RUNNING,MULTICAST,IPv6> mtu 1500 index 2
inet6 2001:1b70:82a1:a:0:4000:3:1/64