Many residental ISPs who provide native IPv6 connectivity provide a /64 delegation to end users by default.
However it is often possible to request larger prefix delegations using DHCPv6-PD. This recipe demonstrates
how to configure a device running Ubiquiti EdgeOS to request a /56 delegation.
For the impatient, you may skip straight to the commands here.
My ISP is Time-Warner Cable (TWC), but these instructions should be applicable to any residential ISP which
supports IPv6 Prefix Delegation.
These instructions have been tested on an Ubiquiti EdgeRouter Lite 3 (ERLite3) running EdgeOS v1.8.0.
However, they should also work on any EdgeRouter model which is capable of running the 1.7.0 or 1.8.0 release.
eth0: WAN
eth1: LAN
eth2: DMZ
set interfaces ethernet eth0 dhcpv6-pd pd 1 interface eth1 prefix-id ':1'
set interfaces ethernet eth0 dhcpv6-pd pd 1 interface eth1 host-address '::1'
set interfaces ethernet eth0 dhcpv6-pd pd 1 interface eth1 service dhcpv6-stateless
set interfaces ethernet eth0 dhcpv6-pd pd 1 interface eth2 prefix-id ':2'
set interfaces ethernet eth0 dhcpv6-pd pd 1 interface eth2 host-address '::1'
set interfaces ethernet eth0 dhcpv6-pd pd 1 interface eth2 service dhcpv6-stateless
set interfaces ethernet eth0 dhcpv6-pd pd 1 prefix-length 56
set interfaces ethernet eth0 dhcpv6-pd rapid-commit enable
set interfaces ethernet eth0 ipv6 address autoconf
set interfaces ethernet eth0 ipv6 dup-addr-detect-transmits 1
I’ve had the best luck with rebooting the router after applying the new configuration. After the restart, the WAN
interface should be assigned an IPv6 address (TWC assigns a /128), and a /56 prefix should be delegated to your
router for assignment.
The “... dhcpv6-pd pd 1 prefix-length 56” statement instructs the router to request a 56-bit prefix delegation, as
recommended by RFC 6177. Other possible prefix lengths include 64, 60,
or 48.
In this example, my ISP has assigned IPv6 address 2001:db8:ffc0:b4:397d:e940:b6b7:8126/128 to eth0, and delegated
the 2001:db8:9d81:d700/56 subnet to my router.
The “... interface eth1 prefix-id ':1'” statement tells dhcpv6 to assign a four-bit Site Level Aggregation ID
(SLA ID, between 00 and ff) of 01 to interface eth1 . This corresponds to the final two hexadecimal digits
of the /64 subnet assigned to the interface.
In this example, the 2001:db8:9d81:d701::/64 subnet is assigned to eth1.
The “... interface eth1 host-address '::1'” statement tells the router to assign an address of 2001:db8:9d81:d701::1/64
to eth1
The “... interface eth1 service dhcpv6-stateless” statement instructs the router to provide DHCPv6 and SLAAC with
Router Advertisement to attached clients on eth1. Other options options are slaac and dhcpv6-stateful.
The output below shows the subnets assigned to each interface.
admin@erlite3:~$ show interfaces ethernet
Codes: S - State, L - Link, u - Up, D - Down, A - Admin Down
Interface IP Address S/L Description
--------- ---------- --- -----------
eth0 10.20.30.40/20 u/u WAN
2001:db8:ffc0:b4:397d:e940:b6b7:8126/128
eth1 2001:db8:9d81:d701::1/64 u/u LAN
eth2 2001:db8:9d81:d702::1/64 u/u DMZ
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