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I'm going to buy a new router, but, I've just realised that for nearly all routers I've looked at (Belkin, Netgear, D-Link) don't state the maximum number of devices which can connect concurrently.

I have a D600 and have now looked on their website, and through the manual and also find no mention of the limit (which I really need to know if there is one due to debugging another issue).

The new router will be a gift for a friend... The issue is, they have 12 devices in their house, all of which will require WiFi and another 3 devices which are to be hard wired.

Since the router websites don't mention any limitations, can I assume there is a general limit on what the number of concurrent connected devices can do or is the issue more about understanding the more devices connected, the less the performance will be due to the sharing of the resource?

My question is, without trying to determine the limit my self manually (plugging in devices until it's maxed out), is there any way to know that a certain device will work with a given number of concurrent connected devices?

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I've seen a lot of routers that were absolute shit in uncountably many ways, but fifteen devices is a piece of cake for even the worst offenders. – Marcks Thomas Feb 25 '14 at 13:38
    
Why are you worried about 15 devices? Worst case scenario: the network becomes slow if all of them max out the pipes. – Navin Feb 25 '14 at 19:24
    
I have seen limits on home based routers. I dont know if they were artificial limits, or hardware based limits. I cant remember buying a router in the past forever, so this was a long time ago. I do remember the hard wired limit was more than I would need and the wireless limit as well. – Keltari Aug 15 '14 at 21:47

11 Answers 11

up vote 12 down vote accepted

There's a (theoretical) absolute limit of 65535 concurrent connections. When using SNAT or MASQUERADE, that is. As such, the maximum feasible number of devices would be somewhere near 800, to account for closing and opening connections.

A TCP connection is uniquely defined by local and remote host and port. As such, the router could establish up to 65,535 connections to the same host and port. At the same time, it could establish another 65,535 connections to another host and port.

That means you can have an overall amount of (local addresses) * (local ports = 65,535) * (remote addresses) * (remote ports = 65,535). Of course, some local ports may not be available (services hosted or port forwarding). However, it’s still more than you’ll ever need.

Naturally, this would require a network larger than /24, which poses no problem with OpenWrt and the like. Without aftermarket firmware, most routers are limited to a /24 network, leaving 253 IP addresses for hosts. Wireless connectivity might be further limited, sometimes greatly.

However, you’ll most likely run into resource exhaustion before you’ll get anywhere near these limits. Connection tracking is very hard.

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Not true. The whole definition of SNAT means there is not a 1-1 correlation between ports and clients (or their number). Furthermore most routers (even with OpenWRT) won't get near that limit before running into other limitations such as RAM, wireless driver(s), arbitrary DHCP limitations, and so forth. – qwertyuiop Oct 6 '15 at 9:44
    
Your point may be valid, whether ports are reused is implementation-dependent, however. Also, I did say “theoretical”. And wireless drivers don’t care about level 3+. – Daniel B Oct 6 '15 at 11:14
    
No, the issue is so vague that there isn't even any theoretical relevance. Nor does not caring about layer 3+ stop there being a limitation on number of layer 2 devices connected. Technically the OP asked about devices, not number of IPs. – qwertyuiop Oct 6 '15 at 11:14
    
No, actually he did not. He asked: “Is there any way to know that a certain device will work with a given number of concurrent connected devices?” – Daniel B Oct 6 '15 at 11:19
    
No, that's exactly what I said. DEVICES. – qwertyuiop Oct 6 '15 at 14:48

I don't know if there is a limit to number of devices which can connect. It would make more sense that most routers are limited by their hardware, and will experience performance degradation as number of devices increase.

This, I suppose, largely depends on the speed of the routers CPU and available RAM, but it also would largely depend on the services running on the router, i.e. is NAT enabled, QoS, VPN, Access control, is wireless open or with password, etc. I think that the amount of traffic that devices make, is also an important factor to the limit.

I think that this also might be the reason why manufacturers do not specify number of devices which can connect, because it depends on many factors.

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Some devices do have hard limits, especially on WiFi. It all depends on the manufacturer and model. – Keltari Feb 28 '14 at 16:02

In theory you can have up to 255 devices connected to your router, but you will obviously see a performance hit. The performance will be determined by the internet connection you are receiving and specific hardware specification of your router.

You will need to balance load over devices in that you can have 20 devices doing very little work fine, or 2 devices with very high load bottling your connection completely. This all depends on what you want to do with your network.

Sound routers put a limit on the DHCP pool available, which you would have to look around your router settings to find (if it's there). If no such information exists then you can assume the above information. For example, on my router I have a listed range of about 100 for maximum performance, but I will never get close to this so it's largely irrelevant to me.

Looking at the [albeit] small snippet of information provided on that router from your source I can't imagine you would notice any issues with the numbers you are working with.DCHP

Source

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Yes of course, each device has to have an IP assigned, so if the DHCP is "shallow", then so will the number of devices which can connect... What a good point. – MyDaftQuestions Feb 25 '14 at 12:31
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This is only if you are using a 24 bit mask (255.255.255.0). Smaller masks mean more hosts. – AbraCadaver Feb 25 '14 at 18:32
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@AbraCadaver actually for a 24 bit mask it's more like 253 connected devices. 256 - the router - broadcast address - network id – Cruncher Feb 25 '14 at 19:18
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@Cruncher: Yes, my point was that's a very low number considering the masks that are available. – AbraCadaver Feb 25 '14 at 19:21
    
If the devices require static DHCP entries many routers are limited to 32. – Phil Feb 26 '14 at 0:43

From my professional experience: unless you are planning to connect hundreds of devices, you don't need to worry about it.
I agree with the responses of @Matthew and @D. Kasipovic, but sometimes the scientific method does not work for predictions.
I work as a computer scientist and I have deployed many (not very big: hotels and restaurants with less than 80 devices connected at the same time) WiFi networks during years (practically from the beginning of wireless 802.11 technology in networks), so I can tell you that my usual method has finally become: buy some router (or access point), install it and... good luck.
If it hangs (or there is any other strange behavior, like reboots or returning to firmware defaults automatically) often, remove it and buy a different model.
Sorry, I wanna be more theorical in my response, but I think you could lose a lot of time researching this. Simply buy any one (except those you know failed in the past).
Do you still want some good behavior model? The best I have found till now:

Buffalo WHR-HP-G54DD
Buffalo WHR-HP-GN

I hve found them to work fine 24 hours a day during months or years with lots of NAT clients connected to WPA WiFi transfering many network data, plus VPN server working, and they have support for DD-WRT firmware. They heat a bit, but it is not a problem if you don't put it in a small closet. Mostly the Buffalo models have proven to be stable. But remember: even them do some times hang (even with low usage and devices connected).

EDIT: Some router models have a very limited (10-20) number of available DHCP Reservation List. This could be important if you are planning to have a fixed correlation between device and IP address. This problem is, too, solved with DD-WRT firmware.

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After the 2010 earthquake in Port-au-Prince I set up a network for a medical crisis center. All we have available in the beginning were the same Linksys AP units as shown in the original article. We had several acting as access points all feeding into one which was the connection to the Internet and the wired network. We had constant problems with them (especially the central router) and fried several. When one of them was giving signs of problems I touched it and found that it was hot enough that I could not pick it up. I do not know what the limits for this unit were but we were obviously exceeding it (we were running between 20 and 200 simultaneous connections).

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There are multiple limiting factors here:

  1. Most WiFi module used in the small cheap WiFi routers have a hard limit of 32 devices per module. I believe that leaves 31 available for connections.

  2. DHCP server on the WiFi router may only support 50 or so devices, that is combining all WiFi and Wired connections. This number can be changed but can be misleading. Each DHCP client leases the IP address for a length of time. Typically 24 hours. So when calculating total active devices, one must also calculate the number of client devices that was active within the last 24 hours, not just those which is currently powered up and active.

  3. NAT pairs. NAT is what enables a connection between your computer and a web server on the internet. Most WiFi router does not publish the total number supported but in the early days of NAT routers, this equals to the number of DHCP clients supported.

Conclusion. If you are not sure or cannot find out those limits, and you find yourself rebooting the WiFi router to get performance. Time to setup a good router and multiple WiFi Access Points.

Using Cheap Access Points, best way is to name them differently per location so loading can be split by connection to different APs.

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While from a technical standpoint you would expect a limit of maybe 255 (as others have mentioned), this seems to be not always the case. Instead there might be much lower limits because of marketing / manufacturer politics.

Germany's most renowned IT magazine c't reported in December 2013 that the access point TP-Link TL-WA701ND only allows 15 WIFI clients (article in German). The article further states that the limit is arbitrarily set by the manufacturer in the firmware because the target market of the device is SOHO (Small Office/Home), and that the limit is not mentioned neither in the manual nor in the technical specification. It is claimed that with OpenWRT the limit should be eliminated, but using alternative firmware may not be acceptable or desired in all cases.

The article does not contain statements about other access points or manufacturers, but it does not present this limit as something unique, rare, or surprising. So I would assume that other devices targeted for SOHO usage may have similar limits. Note that it may not be apparent for which market segment a device is meant at first glance. The access point mentioned here even has features such as Multi-SSID WIFI, VLAN, and Power-over-Ethernet support, all of which I would primarily expect from an access point for professional usage in a larger network.

The article suggests to request a definitive answer on the maximum number of supported clients from the manufacturer prior to buying.

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Just for fun, I checked my router's DHCP page.

As it turns out, I have 23 devices right now, with 3 satellite receivers (plus the WiFi bridge, which has its own IP), 6 mobile devices (smartphones, tablets, etc), 5 computers, 2 video game consoles, an Apple TV, a Slingbox, a Squeezebox, and several virtual machines.

Some of those devices are wired, and some are wireless.

I have no problems with my router.

As far as the maximum number of devices goes: some consumer routers limit you to a 24-bit subnet mask, which limits you to 254 IP addresses on your local network. However, my DLink actually lets me edit the mask, so I could (in theory) use up to a class A network with a 10.x.x.x address.

I would wager that any limits on your home network will be due to ISP bandwidth, and not limits on the actual router box.

I don't think 12 clients will be a problem.

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Based on my experience with wireless routers, most of them out there cannot support more than 255 devices. When the network mask is changed to 22 or 255.255.252.0, all of them that I tried failed to function properly.

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the only limitation would be in the amount of bandwidth your router can transmit. there would be no limit to the number of devices you could connect, however, you would see a performance degradation as you connected more devices.

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I have been doing some searching. Found this on Netgear's site, saying they support 32 devices (64 on dual band).

How many clients can you connect wirelessly to a NETGEAR router?

NETGEAR home routers can accommodate up to 32 clients per wireless band. If your router is dual band, the total wireless clients your router can handle is 64 (32 for the 2.4GHz and 32 for the 5GHz).

However, since the router's wireless channel is shared between all the wireless clients, adding clients will inevitably result in slower network access for all clients. This will be particularly noticeable if some of the clients are using a lot of wireless bandwidth, for example by watching a video or doing a torrent download. Therefore, the maximum number of wireless clients that will operate satisfactorily while connected to the same router will vary depending on what the devices are used for. It will also vary depending on how much wireless congestion or interference are present in the location where the router is installed.

How many clients can you connect wirelessly to a NETGEAR router?

Not all manufacturers are very good at documenting this information.

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I edited your answer to what would be considered to be an acceptable answer. Answers which only contain links are subject to be removed since they are not helpful. Of course this answer barely answers the question proposed even now. – Ramhound Apr 14 at 15:34

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