Adding to this, a note about lightbulbs and doorlocksâŚ
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Most zigbee light link devices, including Phillips Hue bulbs, GE link bulbs, Cree Connectedly bulbs, and Yee Sunflower bulbs can only act as repeaters for other ZLL devices on their own mini network. Not for other zigbee devices. (edited to add: @Savij reports below that the Osram Lightify bulbs do act as ZHA repeaters also.)
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Many zwave lightbulbs, although not all, will in contrast act as repeaters for any nonbeaming zwave devices as long as they are powered on. This can be useful if you need a ceiling mount zwave repeater.
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zwave doorlocks use a special protocol called âbeaming.â Only other zwave devices that support beaming can pass messages on to them. To determine if a device supports beaming, see its official âconformance statementâ on the Z-wave Alliance website.
The following topic explains more about exactly which devices can repeat for which. This is a clickable link.
I know the osram bulbs will act as routers(repeaters) for whatever zigbee network they are joined to. I think the ge bulbs will too.
Check again: they will likely act as repeaters for whatever ZLL network they are joined to, but not for any nearby ZHA devices. So they will repeat for the other bulbs, but not, say, a nearby zigbee sensor. I know thatâs true for GE and Hue. If Osram is different, let us know.
I checked my osram bulb and it will extend the network and act as a zigbee router for all zigbee devices as long as they are connected directly to the ST hub.
Excellent, thanks for checking!
@pstuart says GE has confirmed that their bulbs do not repeat for ZHA devices.
HEALING THE NETWORK TO GET ALL ROUTING TABLES UP TO DATE: ZWAVE REPAIR UTILITY
And here a little more detail on running a Zwave repair, since the blog article above just mentions it in passing. If after reading the information above you decide you want to add a repeater to your network, or if you just suspect that your routing tables may not match your real physical configuration, you can âhealâ the network to improve overall efficiency after youâve added any new devices.
Z-wave repair (also called âhealingâ the network) is a utility that will force every zwave node on your network to rebuild its routing table. This can rescue âorphanâ nodes who are confused about who their nearest neighbors are and consequently have a difficult time getting or receiving messages.
ZIGBEE HEAL: UNPLUG AND PLAY 
For zigbee, healing the networks occurs automatically whenever the hub is powered off for about 15 minutes or more. It may take an hour or two before the routing tables rebuild completely, but you donât have to do anything other than unplug the hub, wait at least 15 minutes, and then plug it back in.
ZWAVE HEAL: RUN THE ZWAVE REPAIR UTILITY
For zwave, though, you have to use the Repair utility. This is available through the IDE. You will see a message in the log that the repair is complete, but thatâs just at the hub, like zigbee it may take an hour or two before all the nodes have rebuilt their tables as well.
REAL LIFE::: RUN A ZWAVE REPAIR 3 TIMES TO CATCH ALL SLEEPING NODES
Most field techs will actually run the zwave repair three times in a row. This allows each hop of the network to be rebuilt.
So for maximum benefit:
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unplug the hub for at least 15 minutes. Then plug it back in.
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run the zwave repair utility. When you see the message in the logs that the repair is complete, wait another 15 minutes (donât unplug the hub this time, though), then do a second zwave repair.
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again when you see the log message that the repair is complete, wait 15 minutes with the hub still plugged in, then do a third zwave repair.
The wait and repeat also improves the odds of catching all nodes, including ones that were asleep during the first pass.
So easy, but a little tedious. You should expect to see improved response rates within a few hours if node address tables were contributing to the problem.
- A FOOTNOTE ABOUT âBENCH INSTALLSâ
if you pair new devices to your hub by always bringing them to the hub, theyâll join the network but they wonât know who their real neighbors are once theyâre in their true locations.
If you only have a few devices and theyâre all close to the hub anyway, it wonât matter. but as you start to add more devices or they get further away, your messages will take âhopsâ to travel across the network, going from neighbor to neighbor.
The problem is if they were all paired right next to the hub, theyâll try to send their messages through neighbors that were close to the hub when they were paired, which may now be out of range.
So doing a bench install is fine, but itâs generally a good idea to then heal the network after everything is in their final location just to make sure each node knows its true neighbors.
I am curious how you were able to check this. Software??
The community-created wiki, things that are smart, includes an article on repeaters that lists specific repeater models that may be of use for specific use cases:
Looks like Christmas lights can be added to the list of things that can interfere with Zigbee.
One more thought. While I understand the marketing reasons for the decision, the fact that SmartThings gives customers zero guidance on how to set up a network backbone does lead to a lot of frustration that shouldnât have to exist. if people knew that
.1) The hub should be located centrally in the home, both vertically and horizontally. Donât put it in a garage or basement as those have concrete and pipes and metal objects which will reduce signal. If your Internet router is off in some inaccessible corner, you can use a Wi-Fi access point that has a ethernet port on the side and plug into that. Also, the hub should not be put in a cabinet. You just want to make it as easy as possible for signal to spread around your house.
.2) you need one device that can repeat about every 40 feet (every 60 feet for Z wave plus).
.3) zigbee repeats only for zigbee and zwave repeats only for Z wave. And Thread repeats only for Thread. The repeaters form the âbackboneâ of the network. So there will be one backbone for zigbee and one backbone for zwave and one backbone for Thread. When installing several devices at once, install the repeaters first, beginning closest to the hub and working outward, so that the other devices will be able to use them to reach the hub. Then go back and install the battery powered devices. Using this method, zwave plus Devices should be able to be paired in place.
Some Z wave classic devices may need to be moved close to the hub to pair, and then moved to their desired location (or you can move the hub close to the device). Z wave locks will need to be paired very close to the hub so that they can exchange an encryption key.
If you do have to change the location of any zwave devices, including moving the hub around, during the join process, you will then need to run a Z wave repair utility once everything is in place to update the neighbor tables.
.4) battery powered devices do not usually repeat, but most mains-powered devices do including most plug-in modules, light switches, in wall relays, and plug in sensors. It is up to the manufacturer though, so check to be sure. Sengled, for example, has made the decision that none of their smart bulbs will repeat.
.5) Z wave plus has the longest range per device of the Z wave/Zigbee/Thread options
.6) The hue bridge forms its own mini network and none of the devices connected to it will repeat for any of your other devices. The same with âMatter bridgesâ like the Aqara M2 hub.
.7) wi-Fi is irrelevant to the performance of zigbee/Z wave devices except that very strong Wi-Fi can drown out nearby Zigbee. For this reason, locate your SmartThings hub at least 3 m from your Wi-Fi router and any Wi-Fi access point.
.8) Different architectural features can make it harder or easier for signal to get through, effectively making the range shorter. For example, foilbacked insulation inside a wall might make it hard to get signal through to the next room. Signal might pass easily from one side to the other when a garage is empty, but be blocked by cars when the garage is full. These kinds of obstacles may require an additional repeater or changing the placement of devices.
.9) Z wave is limited to four total hops per message between the end device and the hub, zigbee allows for 15.
A zwave network is limited to 232 Devices, including the hub. A zigbee network can support many more. so you will theoretically be able to add up to 231 Zwave devices to your SmartThings account at one location, although you may start to encounter some issues if you go over 40, it just varies.
However, as of this writing the smartthings hub can only handle 64 non-repeating zigbee devices connected directly to it. These are most commonly battery operated sensors or the Sengled brand lightbulbs. If you try to connect more than 64 non-repeating zigbee devices directly to the hub, some of them will just drop off the network.
The good news is that every time you add an additional zigbee repeater, it can âparentâ some of the non-repeating Zigbee devices, leaving more slots for the hub again. The number that each new Zigbee repeater could take varies by brand/model, but is typically 3 to 7.
Also, your SmartThings account has a limit on the total number of devices you can add per location, independent of protocol. (As of August 2021, this was 200.)
.10) each end Device keeps a list of its closest neighbors. Anytime you add a new device to the network or physically relocate a device, you should run the Z wave repair utility for Z wave devices or do a zigbee heal for zigbee devices to make sure that all the neighbor tables are up-to-date. (Thread should handle these updates automatically for thread devices.)
To do a zigbee heal, take the hub off power (including removing the batteries) and leave it off for at least 20 minutes. When you put the hub back on power, all the individuals zigbee devices will automatically update their neighbor tables.
To do a Z wave repair, follow these instructions:
This process can take a while for both Z wave and zigbee, so you may not see efficiency improvements until the next day.
The automated routing algorithms take into account a lot of information that we as humans donât have like network traffic and signal strength.
Unfortunately, at the time of this posting (December 2023) smartthings does not provide us with any routing information. It may be possible to add a third-party device to your system and run its own diagnostics, but that can be expensive and somewhat complicated. There are threads in the forum about how to do it if you want to, but most people donât.
People would then know 95% of what they need to know to set up an efficient mesh network. One line in the hub user manual âgo online for information on how to set up the most efficient communication network for your home automation devicesâ and a one page web explantation of those ten points and youâd save a lot of support calls.
Professionally installed systems, even Xfinity home, obviously donât have to do that. Their installers will deal with those issues.
But I do think it makes sense to provide the backbone planning information for a DIY system.
JMO 
Do we know if the Zigbee and Z-wave antenae orientations are still the same as the illustration in that blog post? It looks like an older hub.
On point as always, JD. Thanks!
Question on fail over if a repeating node fails.
For zwave, if a repeater fails, battery powered endpoints seem to find the next repeater on their own.
For zigbee, if a repeater fails, the battery powered endpoint cant seem to find another.
What is the expected functionality?
If a battery powered device (zigbee in this case) is mobile, and goes in and out of range between 2 repeaters, will it be able to jump back and forth? Will zwave?
What you just described in the moment, although over time itâs different⌠Zigbee battery powered devices select a âparentâ when they join and thatâs the device that they expect to be the first repeater. They should also be able to reach the hub if itâs one hop. But if the parent dies and they are on the edge of the network, they can get âorphaned.â The hub is supposed to notice that the orphan has not checked in for a while and then there are a couple of different things that can happen which will either rebuild the network by giving the child to a new parent, or if a new parent is not available, Mark the child as unavailable. How quickly all of this happens depends on the zigbee profile being used and some individual manufacturer settings. On the other hand, if you just take the hub itself off of power and leave it off for 15 or 20 minutes, then all the devices will basically remap themselves when the hub comes back online and that cleans up anything involving defective devices as long as another parent is available. So most commercial installations will force a network heal once a week or so. All of which means that eventually, the child device will probably find a new parent unless there just isnât one available in which case the hub should know that.
Z wave, however, has two different mechanisms for providing alternate routes more quickly. First of all, most devices are aware of a couple of alternate routes to begin with. Second, through âexplorer framesâ zwave plus devices and some of the older generation can eventually rebuild paths around failing devices, although it can take a couple of days. You can also issue a ârepairâ utility command to force the network to rebuild. A lot of zwave only platforms do a repair every night to keep things clean, but smart things has always recommended against that because they have additional synchronization issues due to the cloud.
So in practice if you are using smartthings a zwave end device probably has a better Chance of finding an immediate alternate path. Zigbee may require power cycling the hub to get things cleaned up. But both protocols do have housekeeping methods that should automatically improve messaging over time after a device goes defective. So both protocols are considered âself healing networks.â
For more information, see the resources on the various alliance sites.
@JDRoberts - some really helpful information here - especially post 11!
Can An Amazon Echo device (with Smart Hub) be a Zigbee repeater device for a SmartThings Hub?
Iâm not sure how they would pair however as each is really a Hub and not a âdeviceâ per se??
Unfortunately you are correct: the echo device is another primary coordinator, and the Zigbee profile that smartthings uses allows for only one primary coordinator per network. So you cannot add an echo device to your smartthings Zigbee network, and therefore it cannot be a repeater for that network.
Ikea Tradfri plug in pocketsockets happened to be good repeaters for a SmartThings set up, and are very inexpensive, less than $10 when bought directly from IKEA. And they are available in a number of other countries as well.
I see there is also a Tradfri signal repeater - that looks like a USB adapter (as well as a repeater) so that is an alternative too I suppose - depends on your preference as to whether you want to have a smart outlet or a USB 
12.99 vs 9.99 for the outlet/repeater.
The Tradfri signal repeater is specifically designed to work with their battery operated shades. It reportedly has a slightly weaker signal than the plug-in pocket socket. So I donât recommend it for this purpose. But choice is good. And like you say, if itâs a place where you would put a plug in USB charger anyway, it may be the right choice. 