dhcpv6-mod allows Unifi Gateways (UDMs, UDR, UCGs) to provide DHCP V6 client options required by some ISPs (e.g. Orange France), enabling dual IPv4 and IPv6 internet connection.

You need UnifiOS 3.2.9 at least to use dhcpv6-mod (4.x is recommended as I can no longer test in v3).

Since we cannot configure specific DHCPv6 client options in the WAN settings, this mod automatically generates them using the DHCPv4 options you've already set in Unifi Network UI.

If you don't want dhcpv6-mod's default DHCPv6 options (designed for Orange France ISP), you can configure your own options (see the Initialize DHCPv6 config file section).

Important note : after any non-documentation commit of this repo, or if you update your config file, or after a firmware update, don't forget to run install-dhcpv6-mod.sh again (see Install or update dhcpv6-mod)

• How does it work ?
• Download dhcpv6-mod files
• Initialize DHCPv6 config file
• Install (or update) dhcpv6-mod
• Activate DHCPv6 WAN client
• Check IPv6 lease and connectivity
• Fully activate IPv6 on LAN
• Uninstalling dhcpv6-mod

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As a prerequisite, you must have entered all the DHCP V4 WAN options required by your ISP, using Unifi's Network WAN1 settings. Your IPv4-only WAN access must already work before installing dhcpv6-mod.

Installation of dhcpv6-mod will rename Unifi's /usr/sbin/odhcp6c as /usr/sbin/odhcp6c-org, and copy odhcp6c.sh file to /usr/sbin/odhcp6c.

The new /usr/sbin/odhcp6c will :

• Fetch the active DHCPv4 options values using the ubios-udapi-client API
• Prepare the DHCPv6 options, as configured in /data/local/etc/dhcpv6.conf
• Finally, exec Unifi's original binary (now odhcp6c-org) using the DHCPv6 options

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You need SSH access to your Unifi router root account.

Download the repository files in the /data/dhcpv6-mod directory (note: /data is persisted after reboots, including after firmwares upgrades).

You can either use git to clone this repo (recommended) :

cd /data
git clone https://github.com/fgero/dhcpv6-mod.git

...or alternatively download the files with curl :

cd /data
curl -sL https://github.com/fgero/dhcpv6-mod/archive/refs/heads/main.tar.gz | tar -xvz
mv dhcpv6-mod-main dhcpv6-mod

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The installation script will automatically create a /data/local/etc/dhcpv6.conf config file, with Orange settings by default.

Here are the 4 DHCP options that are, by default, propagated from V4 to V6, with transformations for V6 option 16 and option 1 (see RFC8415) :

If you don't want these Orange France ISP standard settings, the first time you install dhcpv6-mod, you must create and customize your own /data/local/etc/dhcpv6.conf file before moving to the next section (installation) : please refer to CONFIGURE.md.

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Go to the directory we just cloned, and run the install/update script :

cd /data/dhcpv6-mod
./install-dhcpv6-mod.sh

root@UCG-Max:/data/dhcpv6-mod# ./install-dhcpv6-mod.sh
[install-dhcpv6-mod] copied dhcpv6-orange.conf default config to /data/local/etc/dhcpv6.conf
[install-dhcpv6-mod] /usr/sbin/odhcp6c detected as an original Unifi executable, we can rename it
[install-dhcpv6-mod] /usr/sbin/odhcp6c renamed /usr/sbin/odhcp6c-org
[install-dhcpv6-mod] /usr/sbin/odhcp6c now replaced by ./odhcp6c.sh
[restart-dhcp-clients] Restarting DHCPv4 (udhcpc) and DHCPv6 (odhcp6c) clients to take updates into account
[restart-dhcp-clients] (this will initiate a DHCPv4+v6 Discover process, and should not interrupt your connection...)
[restart-dhcp-clients] Restart done, you can now check dhcp client logs with :
grep -E 'dhcpc|odhcp6c|dhcpv6-mod' /var/log/daemon.log

Note : if you add -f to the install command, a filtered tail -f /var/log/daemon.log will automatically be executed at the end (you must Control-C to exit).

The install-dhcpv6-mod.sh command must be issued :

• when installing dhcpv6-mod for the first time, of course
• when dhcpv6-mod repository gets an update commit (except when the update is documentation-only)
• when you update your own configuration file (/data/local/etc/dhcpv6.conf)
• after a firmware update reboot (i.e. Unifi OS update)

Conversely, running install-dhcpv6-mod.sh is NOT needed after a "normal" reboot (i.e. no firmware update), as dhcpv6-mod is not removed in that situation : IPv6 will continue to work.

During the first installation the /data/local/etc/dhcpv6.conf configuration file will be created ONLY if it doesn't already exist, using dhcpv6-orange.conf file content.

In fact, the ./install-dhcpv6-mod.sh command can be run at any time, as it will update /usr/sbin/odhcp6c with a new version of odhcp6c.sh only if needed.

In addition, if /usr/sbin/odhcp6c has been updated OR if your config file is newer than the running odhcp6c process then the script will finish by calling ./restart-dhcp-clients.sh.

The ./restart-dhcp-clients.sh script, which can also be called manually, will restart both DHCP v4 and v6 clients (full DHCP discover sequence for both, without interrupting the WAN connection).
In that case, it is advisable to check WAN access and in particular Check IPv6 lease and connectivity.
You can also use the -f option if you want to follow the daemon.log.

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In the Network UI, go to Network > Settings > Internet > click on Primary (WAN1)

For Orange, you must already have set VLAN ID (832), MAC Adress clone of your Livebox, DHCP client options (V4) 60/77/90, and DHCP CoS 6.
In any case, you must have a working WAN IPv4 connection, with all V4 options required by your ISP.

Next, you need to set IPv6 Connection to DHCPv6 (instead of Disabled) and to configure Prefix Delegation Size (for Orange, to 56 instead of 64), like so :

Then, the ubios-udapi-server process should automatically fork, in addition to udhcpc (V4 client), a new process running our own odhcp6c (which will immediately exec /usr/sbin/odhcp6c-org), with all the V6 client parameters passed :

# ps -ef | grep dhcp
root     2574251    4134  0 Jun18 ?        00:00:00 /usr/bin/busybox-legacy/udhcpc --foreground --interface eth4.832 --script /usr/share/ubios-udapi-server/ubios-udhcpc-script --decline-script /usr/share/ubios-udapi-server/ubios-udhcpc-decline-script -r <publicIPv4> -y 6 --vendorclass sagem -x 77:<userclass_hex> -x 90:<auth>
root     2574252    4134  0 Jun18 ?        00:00:00 /usr/sbin/odhcp6c-org -a -f -K6 -R -r11,17,23,24 -V <pfx+vendorclass> -c <pfx+clientid> -u <userclass_string> -x 11:<auth> -v -s /usr/share/ubios-udapi-server/ubios-odhcp6c-script -D -P 56 eth4.832

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You can check the DHCP V6 discover and lease process from the daemon.log :

grep -E 'dhcpc|odhcp6c|dhcpv6-mod' /var/log/daemon.log

2023-07-17T15:45:26+02:00 UDR odhcp6c[2540864]: Starting RELEASE transaction (timeout 4294967295s, max rc 5)
2023-07-17T15:45:26+02:00 UDR odhcp6c[2540864]: Send RELEASE message (elapsed 0ms, rc 0)
2023-07-17T15:45:26+02:00 UDR ubios-udapi-server[2540863]: udhcpc: received SIGTERM
2023-07-17T15:45:26+02:00 UDR ubios-udapi-server[3018621]: udhcpc: started, v1.34.1
2023-07-17T15:45:27+02:00 UDR ubios-udapi-server[3018622]: [dhcpv6-mod] Selected DHCPv6 client executable (with support for CoS) : /usr/sbin/odhcp6c-org
2023-07-17T15:45:27+02:00 UDR ubios-udapi-server[3018622]: [dhcpv6-mod] Found ubios-udapi-server JSON config in /data/udapi-config/ubios-udapi-server/ubios-udapi-server.state
2023-07-17T15:45:27+02:00 UDR ubios-udapi-server[3018622]: [dhcpv6-mod] Fetched DHCPv4 option 60 : length=5 value=s...m
2023-07-17T15:45:27+02:00 UDR ubios-udapi-server[3018622]: [dhcpv6-mod] Fetched DHCPv4 option 77 : length=43 value=FSVDS...ebox3
2023-07-17T15:45:27+02:00 UDR ubios-udapi-server[3018622]: [dhcpv6-mod] Fetched DHCPv4 option 90 : length=140 value=00000...xxxxx
2023-07-17T15:45:27+02:00 UDR ubios-udapi-server[3018622]: [dhcpv6-mod] Fetched MAC Address Clone : length=12
2023-07-17T15:45:27+02:00 UDR ubios-udapi-server[3018622]: [dhcpv6-mod] Fetched DHCPv4 CoS of 6
2023-07-17T15:45:27+02:00 UDR ubios-udapi-server[3018622]: [dhcpv6-mod] Found dhcp6c options file /data/local/etc/dhcpv6.conf
2023-07-17T15:45:27+02:00 UDR ubios-udapi-server[3018622]: [dhcpv6-mod] Generated DHCPv6 CoS of 6 (default is to set to the same value as DHCPv4 CoS)
2023-07-17T15:45:27+02:00 UDR ubios-udapi-server[3018622]: [dhcpv6-mod] Generated DHCPv6 option 1 : length=20 value=0003...xxxx (clientid, -c )
2023-07-17T15:45:27+02:00 UDR ubios-udapi-server[3018621]: udhcpc: broadcasting discover
2023-07-17T15:45:27+02:00 UDR ubios-udapi-server[3018763]: [info ] ubios-dhcpc-decline-script: DHCP offer 90.xx.xx.xxx/21 on interface eth4.832, gateway: 90.xx.xx.1
2023-07-17T15:45:27+02:00 UDR ubios-udapi-server[3018622]: [dhcpv6-mod] Generated DHCPv6 option 11 : length=140 value=00000...xxxxx (authentication, -x 11:)
2023-07-17T15:45:27+02:00 UDR ubios-udapi-server[3018763]: [info ] ubios-dhcpc-decline-script: DHCP offer 90.xx.xx.xxx/21 accepted
2023-07-17T15:45:27+02:00 UDR ubios-udapi-server[3018621]: udhcpc: broadcasting select for 90.xx.xx.xxx, server 80.xx.xxx.x
2023-07-17T15:45:27+02:00 UDR ubios-udapi-server[3018622]: [dhcpv6-mod] Generated DHCPv6 option 15 : length=43 value=FSVDS...ebox3 (userclass, -u )
2023-07-17T15:45:27+02:00 UDR ubios-udapi-server[3018622]: [dhcpv6-mod] Generated DHCPv6 option 16 : length=22 value=00000...7656D (vendorclass, -V )
2023-07-17T15:45:27+02:00 UDR ubios-udapi-server[3018622]: [dhcpv6-mod] Successfully generated 4 DHCPv6 options using /data/local/etc/dhcpv6.conf
2023-07-17T15:45:27+02:00 UDR ubios-udapi-server[3018622]: [dhcpv6-mod] Launching exec /usr/sbin/odhcp6c-org -a -f -R -r17,23,24 -K6 -c 0003...xxxx -x 11:00000...xxxxx -u FSVDS...ebox3 -V 00000...7656D  -v -s /usr/share/ubios-udapi-server/ubios-odhcp6c-script -D -P 56 eth4.832
2023-07-17T15:45:27+02:00 UDR odhcp6c[3018622]: (re)starting transaction on eth4.832
2023-07-17T15:45:27+02:00 UDR ubios-udapi-server[3018621]: udhcpc: lease of 90.xx.xx.xxx obtained from 80.xx.xxx.x, lease time 604800
2023-07-17T15:45:28+02:00 UDR odhcp6c[3018622]: Starting SOLICIT transaction (timeout 4294967295s, max rc 0)
2023-07-17T15:45:28+02:00 UDR odhcp6c[3018622]: Got a valid ADVERTISE after 13ms
2023-07-17T15:45:28+02:00 UDR odhcp6c[3018622]: IA_NA 0001 T1 0 T2 0
2023-07-17T15:45:28+02:00 UDR odhcp6c[3018622]: IA_PD 0001 T1 84672 T2 483840
2023-07-17T15:45:28+02:00 UDR odhcp6c[3018622]: 2a01:xxxx:xxx:xxxx::/56 preferred 604800 valid 604800
2023-07-17T15:45:30+02:00 UDR odhcp6c[3018622]: Starting SOLICIT transaction (timeout 4294967295s, max rc 0)
2023-07-17T15:45:30+02:00 UDR odhcp6c[3018622]: Got a valid ADVERTISE after 10ms
2023-07-17T15:45:30+02:00 UDR odhcp6c[3018622]: IA_PD 0001 T1 84672 T2 483840
2023-07-17T15:45:30+02:00 UDR odhcp6c[3018622]: 2a01:xxxx:xxx:xxxx::/56 preferred 604800 valid 604800
2023-07-17T15:45:31+02:00 UDR odhcp6c[3018622]: Starting REQUEST transaction (timeout 4294967295s, max rc 10)
2023-07-17T15:45:31+02:00 UDR odhcp6c[3018622]: Send REQUEST message (elapsed 0ms, rc 0)
2023-07-17T15:45:31+02:00 UDR odhcp6c[3018622]: Got a valid REPLY after 124ms
2023-07-17T15:45:31+02:00 UDR odhcp6c[3018622]: IA_PD 0001 T1 84672 T2 483840
2023-07-17T15:45:31+02:00 UDR odhcp6c[3018622]: 2a01:xxxx:xxx:xxxx::/56 preferred 604800 valid 604800
2023-07-17T15:45:31+02:00 UDR odhcp6c[3018622]: T1 84672s, T2 483840s, T3 604800s
2023-07-17T15:45:31+02:00 UDR odhcp6c[3018622]: entering stateful-mode on eth4.832
2023-07-17T15:45:31+02:00 UDR odhcp6c[3018622]: Starting <POLL> transaction (timeout 84672s, max rc 0)

In that output, here for Orange ISP, we can see that you asked and got a /56 prefix (7 bytes), like 2a01:xxxx:xxx:xx00:, and the 8th byte (00) is reserved by your router/box, you can use 01 to FF (254 subnets of /64)

If you haven't got a ADVERTISE and REPLY within a few minutes, you can try to reset again both DHCP v4 and v6 sequences :

# add -f to follow the daemon.log
./restart-dhcp-clients.sh

Explanation : this script sends a SIGUSR2 to udhcpc to force a DHCPv4 RELEASE, as Unifi does not set the -R option to do that before stopping. Then it sends a SIGTERM to both udhcpc and odhcp6c to stop them (odhcp6c will automatically perform a RELEASE). Then, immediately, both process will be restarted by ubios-udapi-server, starting a full DISCOVER sequence for V4 and V6.

If you haven't used the -f option, you can look at the result a few seconds later :

grep -E 'dhcpc|odhcp6c|dhcpv6-mod' /var/log/daemon.log

If you just need to check the log generated by odhcp6c.sh, in order to see DHCPv6 option generation :

grep dhcpv6-mod /var/log/daemon.log

Even after acquiring a V6 lease, your WAN interface will not get a public IPV6 address, this is expected (apparently) in a V4+V6 (double stack) situation.

Also commands like ping -6 will not work unless you do the following :

If you want to use IPV6 also within your LAN, or even just to test IPv6 connectivity, you must configure your Networks in the UI (at least the Default Network) with IPv6 Interface Type set to Prefix Delegation instead of None.

Warning : as a first step, just to be safe, I suggest to only change the Default Network and leave unchecked Router Advertisment (RA) (ie. disabled)

Then, if you do that, after a few seconds, you can check if the main bridge (br0) got an IPv6 address, and test WAN IPv6 connectivity from the UDR/UDM :

# ip -6 addr show scope global dynamic
47: br0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 state UP qlen 1000
    inet6 2a01:xxxx:xxx:xxxx::1/64 scope global dynamic
       valid_lft 541988sec preferred_lft 541988sec
# ping -6 google.com
PING google.com(par10s22-in-x0e.1e100.net (2a00:1450:4007:80e::200e)) 56 data bytes
64 bytes from par10s22-in-x0e.1e100.net (2a00:1450:4007:80e::200e): icmp_seq=1 ttl=117 time=2.38 ms
(...)
# curl -6 ipv6.google.com -I
HTTP/1.1 200 OK
(...)

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In the previous section, you already have set IPv6 Interface Type to Prefix Delegation, but with RA disabled, and you could validate the WAN IPv6 connectivity.

Next, you can optionnaly check Router Advertisment (RA) (so enable RA) for some Network(s) when you want devices to dynamically get IPv6 addresses.

Note This can lead to issues in some use cases, depending on your LAN and WLAN devices configurations...you'll have to carefully test everything.

Go to Network > Settings > Networks > Choose one > click "IPv6" switch, then :

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You just have to restore Unifi's original odhcp6c binary, like so :

mv /usr/sbin/odhcp6c-org /usr/sbin/odhcp6c`

and then restart the clients :

./restart-dhcp-clients.sh`

In the UI, go to Network > Settings > Internet > Primary (WAN1), and set IPv6 Connection to Disabled (instead of DHCPv6).

Do the same with any Network for which you have enabled IPv6 Interface Type to any other than Disabled.

Then, the odhcp6c process should stop within a few seconds.

You can reactivate it later by changing the same settings to DHCPv6.

When you update your applications from Unifi UI, wget commands are launched in the background, to download the new firmware binaries.

Unfortunately, as of July 2023 at least, Unifi's IPV6 endpoints for fw-download.ubnt.com are unreachable.

And, as Unifi does not use wget options like --connect-timeout=10 or the --prefer-family=IPv4, the default is to try the first adress returned by the DNS resolver, which is IPV6 in our case, and this will wait forever and not perform the desired update

So we need to use the .wgetrc file to change the default behaviour of wget commands :

Note If you used the install-dhcpv6-mod.sh script to install, as you should have, then the fix is already done for you, this is for information or check

grep -sq '^prefer-family' /root/.wgetrc || echo 'prefer-family = IPv4' >> /root/.wgetrc