Powerline adapters and IPv6

My home network includes a number of devices connected via Powerline (HomePlug) adapters. Back in 2015 I blogged about ‘crosstalk’ between my and my neighbour’s home networks, both of which use Powerline adapters (see my post ‘Waiting for 192.168.1.254…’ (Why I could not access a home hub’s management page)), which I was able to resolve by changing the encryption key so that it is different to the default key used by my neighbour. Since then the Powerline adapters have worked well. However, an unrelated network problem recently highlighted another problem with my Powerline adapters…

In November last year there was an external fault with the broadband service to my house, so I had to contact my ISP (the company BT) to fix the problem. BT does not use highly-skilled field personnel to diagnose broadband problems; they tend to use a ‘shotgun’ approach to problem solving. Their first attempt was to replace my router, a BT Home Hub 5, which I knew was actually working perfectly. I was not going to argue, though, because they replaced the router with the newest model, a BT Smart Hub 2. Unlike the Home Hub 5, the Smart Hub 2 fully supports IPv6. BT’s broadband network has supported IPv6 for several years (see ISPreview – UPDATE All BT Broadband Lines Now Support IPv6 Internet Addresses) so I was expecting the computers on my home network to be assigned IPv6 addresses, but ‘ifconfig‘ and ‘ip address‘ showed they were not being assigned IPv6 addresses when connected via the Powerline adapters, only when connected to the Smart Hub 2 via Wi-Fi.

All my computers have IPv6 enabled:

$ sudo sysctl -a | grep disable_ipv6
[sudo] password for fitzcarraldo: 
sysctl: net.ipv6.conf.all.disable_ipv6 = 0
reading key "net.ipv6.conf.all.stable_secret"
sysctl: reading key "net.ipv6.conf.default.stable_secret"
net.ipv6.conf.default.disable_ipv6 = 0
sysctl: reading key "net.ipv6.conf.eno1.stable_secret"
net.ipv6.conf.eno1.disable_ipv6 = 0
sysctl: reading key "net.ipv6.conf.lo.stable_secret"
net.ipv6.conf.lo.disable_ipv6 = 0
sysctl: net.ipv6.conf.wlp2s0.disable_ipv6 = 0
reading key "net.ipv6.conf.wlp2s0.stable_secret"
$ test -f /proc/net/if_inet6 && echo "IPv6 supported" || echo "IPv6 not supported"
IPv6 supported

The fact that the computers on the home network were allocated an IPv6 address when connected to the Smart Hub 2 via Wi-Fi, and that WhatIsMyIPAddress.com confirmed the BT broadband public network was also allocating an IPv6 address, made me suspect the problem of no IPv6 via the wired network was due to the Powerline adapters.

As more machines were added to my home network over the years, I had to buy more Powerline adapters. In 2014 I bought some NETGEAR XAVB5221 (500 Mbps) Powerline adapters to supplement the superseded model NETGEAR XAVB1301 (200 Mbps) Powerline adapters I bought in 2012. Powerline adapters conforming to the HomePlug AV standard work together, so these had no problem communicating. A schematic diagram of my home network is shown below. To keep things simple, only some of the devices are shown. As you can in the diagram, a NETGEAR XAVB1301 adapter was used to connect the BT Smart Hub 2 to the network; some of the computers were connected via NETGEAR XAVB5221 adapters, and others via NETGEAR XAVB1301 adapters.

Simplified schematic diagram of my original home network

I could find no mention of IPv6 for its Powerline adapters in NETGEAR’s documentation and on the NETGEAR Web site. The NETGEAR user manual for the XAV1301 is dated ‘September 2011’ and it lists, under SPECIFICATIONS, compliance with IEEE 802.3 and IEEE 802.3u. The data sheet (no user manual available) for the XAVB5221 is dated ‘2014’ and it lists, under SPECIFICATIONS, compliance with IEEE 1901 and IEEE 802.3.

The Wikipedia page for IEEE 1901-2010 mentions IPv6, so support for IPv6 is relevant to the protocol:

“An IETF RFC Draft address the higher layers of the protocol, namely the specifics of passing IPv6 packets over the PHY and MAC layers of PLC [power-line communication] systems like IEEE 1901.”

I think the following draft Internet Engineering Task Force (IETF) document must be the latest version of the IETF Draft mentioned on the above-mentioned Wikipedia page for IEEE 1901:

Transmission of IPv6 Packets over PLC Networks

Anyway, all this lead me to wonder if the NETGEAR XAVB1301 does not fully comply with IEEE 1901 and does not support IPv6. So I decided to try connecting the BT Smart Hub 2 to the network via a NETGEAR XAVB5221 adapter instead of the older model XAVB1301, as shown in the schematic diagram below.

Simplified schematic diagram of my latest home network

What I then found was that any computer connected to the network via a NETGEAR XAVB5221 adapter was assigned an IPv6 address in addition to an IPv4 address, and WhatIsMyIPAddress.com showed public IPv6 and IPv4 addresses in a Web browser on the device. However, any computer connected to the network via a NETGEAR XAVB1301 adapter was assigned an IPv6 address in addition to an IPv4 address but WhatIsMyIPAddress.com displayed ‘IPv6 not detected’ in a Web browser. So it transpired that NETGEAR XAVB5221 adapters can handle IPv6 but the older XAVB1301 model cannot.

Although not essential, I toyed with the idea of replacing the older NETGEAR XAVB1301 adapters with XAVB5221 adapters, but that model is no longer on sale. The latest available Powerline adapter model from NETGEAR for wired networking is the PL1000 (1000 Mbps). However, its documentation does not mention IPv6 or IEEE 1901, and the following question on the Amazon UK Web site about IPv6 support for the PL1000, and NETGEAR’s answer on 5 May 2020 makes it clear that the PL1000 does not support IPv6:

Question: Does this model support ipv6? netgear xav1301 adapters only support ipv4. my router & pcs support ipv6 but can’t use ipv6 with my xav1301 adapters.

Answer: Thank you for your interest in the NETGEAR PL1000.

The PL1000 supports IPv4.

If you have any questions, you can also check out our NETGEAR Community at any time.

Best regards,
NETGEAR Amazon UK

Unlike NETGEAR, the TP-Link Web site makes it clear that all TP-Link Powerline adapters currently on sale support IPv6:

Most frequently asked questions about TP-Link powerline devices – Part3: Other questions about Powerline Device

Q3.12: Can TP-Link Powerline devices transfer IPv6 packets?

A: Yes, all the on sale TP-Link powerline devices can transfer IPv6 packets. Kindly note this is supported by default and does not require any configuration, our powerline products do not have setting entries for IPv6 either.

I also asked someone I know who uses TP-Link Powerline adapters and a BT Smart Hub 2, and he confirmed that the TP-Link adapters can handle IPv6.

Therefore, the bottom line is: if you want to use Powerline adapters and IPv6, avoid buying NETGEAR Powerline adapters and look at other manufacturers’ adapters instead. I have only investigated TP-Link’s adapters, which do support IPv6. A number of other companies also manufacture Powerline adapters, but you would need to check if they support IPv6; if necessary contact the manufacturer to be sure.

‘Waiting for 192.168.1.254…’ (Why I could not access a home hub’s management page)

I had not been able to access the Manager of the BT Home Hub 3 on my home network to view and configure the hub’s settings. All the network’s users could access the Internet, and I could ping the hub, but trying to access the BT Home Hub Manager from a Web browser resulted in the message ‘Waiting for 192.168.1.254…’. The same thing happened whatever the PC, OS, browser and method of connection (wired or wireless). Sometimes, after about ten minutes or so, an incomplete Manager page would appear, but usually the browser would just display ‘Waiting for 192.168.1.254…’ forever.

I should point out that my Ethernet wired connections use Powerline adapters (HomePlug) connected to the mains wiring of my semi-detached house.

Actually, I did find a temporary work-around to enable me to access the Home Hub Manager. If I switched off then on the power supply to the Home Hub I could access the Manager for a short period (the time varied, but typically was less than half an hour). Then I would be back in the same position of seeing ‘Waiting for 192.168.1.254…’ in a browser window if I tried later to access the Manager. Although I do not need to access the Home Hub Manager often, it was still a nuisance to have to cycle the power to the hub every time I needed to access the Manager.

Searching the Web, it seems this is quite a common problem and can occur irrespective of the manufacturer of the hub (or router) and its IP address. In some cases users have fixed the problem by upgrading the hub’s firmware or by performing a ‘factory reset’ of the hub, but some users never found a solution.

In my case, the BT Home Hub 3 has the latest available version of firmware installed. Not only did I check that via the Web, I also checked the firmware version of another BT Home Hub 3 in the house of someone I know who lives in another town. The curious thing was that he has no trouble accessing the BT Home Hub Manager (also IP address 192.168.1.254).

So I decided to perform a ‘factory reset’ of the Home Hub, but that made no difference.

Then, after many hours searching the Web, I found a thread about a similar problem with a different model of hub: Can’t access BT HomeHub 4? But I’m online ok?. A post by user troublegum in that thread made me sit up:

I still reckon it’s the homeplugs. Regardless of whether your PC is connected to it or not, If one of them is connected to your neighbour’s as well as your router, then it’s going to put 2 DHCP servers on your network.

Disconnect the homeplug from the router, renew your DHCP lease if necessary and try again.

Even before finding that thread I had wondered if the problem was somehow linked to my use of Powerline (HomePlug) adapters.

It seems that, if one PC on a home network is connected to the Home Hub via a Powerline adapter AND a neighbour also happens to be using Powerline adapters AND his single-phase mains house wiring is somehow linked to yours (which is unusual, as adjacent houses are normally connected to a different mains phase), there is the possibility that none of your PCs will be able to access the Home Hub Manager (even if they are connected directly to the Home Hub by Ethernet cable or Wi-Fi rather than via a Powerline adapter).

I have been using Powerline (HomePlug) adapters successfully for about nine years. In late December 2012 I changed from HomePlug 1.0 adapters (14 Mbps) to HomePlug AV adapters (200 Mbps). HomePlug 1.0 adapters and HomePlug AV adapters can operate concurrently over the same mains wiring but can only communicate with adapters of the same standard. The problem of not being able to access the Home Hub Manager started two or three years ago, so I assume that either my neighbour began using Powerline adapters at that time or, coincidentally, I changed to the same standard and manufacturer of Powerline adapter he uses.

Powerline adapters each have a non-volatile encryption key, intended to enable separate Powerline networks to co-exist on the same mains wiring by using a different encryption key for each network.

Since the end of December 2012 I have been using NETGEAR XAVB1301 200 Mbps Powerline adapters but had not bothered to change the encryption key in them (they all come configured with the factory default encryption key ‘HomePlugAV’). If my neighbour happens to be using Powerline adapters with the same default encryption key, and a hub with the same IP address as mine, we would both have two DHCP servers on the same network.

So I changed the encryption key on each of the four Powerline adapters I use:

  • Ethernet connection from the BT Home Hub to a mains socket in the Lounge.
  • Ethernet connection from a PC to a mains socket in the Lounge.
  • Ethernet connection from a laptop to a mains socket in my upstairs office.
  • Ethernet connection from a laptop to a mains socket in a bedroom.

It is supposed to be easy to set the encryption key in the model of Powerline adapter I use. You have to press a button on one adapter for 2 seconds, then a button on the next adapter for 2 seconds, and so on. You have to do them all within 2 minutes. The adapters only generate an encryption key once, so if you want to repeat the process you first have to press a recessed Factory Reset button on all the adapters.

However, despite following to the letter the instructions in the NETGEAR manual, I could not get all four adapters to connect to the network. So I downloaded the NETGEAR Powerline Universal Utility, installed it on the PC running Windows 10 in my lounge, connected the Ethernet port of that PC to one of the Powerline adapters and plugged it into a mains wall socket, plugged the other three Powerline adapters into a multi-socket mains adapter and plugged that into a mains wall socket in the lounge, launched the Powerline Universal Utility and I allocated all four adapters the same encryption key. Each adapter has its own MAC address, serial number and ‘Device Password’ (PWD) printed on it, and the NETGEAR utility program required me to enter the relevant PWD for each MAC address. Then I entered an encryption key (any string of characters of my choice) and clicked a button to set the adapters to use that encryption key. As that encryption key is different to the default key used by my neighbour, the two networks can now coexist without interfering with each other.

NETGEAR Powerline Utility showing my four Powerline adapters

NETGEAR Powerline Utility showing my four Powerline adapters.

The use of the NETGEAR Powerline utility program is explained in NETGEAR’s ‘How To’ How to set the Encryption Key for the Powerline adapter network using the Powerline utility.

Problem finally solved! I can now access the Home Hub Manager without any trouble. And, as a bonus, Internet access seems a little quicker.