how many devices can you have on wifi on a router

unforeseen

There is a hard limit. It's decided by the firmware writers for the reasons that I stated. Nothing to do with DHCP. My router is capable of 4 private lans with their own DHCP allocations. I can make them /8 if I wish but I am still limited to a maximum of 253 clients because any more than that will fail to get a lease because the table is full.

Normally it is a lot higher than most people will use so they never get a problem. The standard tends to be 253 clients possibly because there is a commonality in the core functions regardless of make of router

arciere

unforeseen wrote: »

There is a hard limit. It's decided by the firmware writers for the reasons that I stated. Nothing to do with DHCP. My router is capable of 4 private lans with their own DHCP allocations. I can make them /8 if I wish but I am still limited to a maximum of 253 clients because any more than that will fail to get a lease because the table is full.

Normally it is a lot higher than most people will use so they never get a problem. The standard tends to be 253 clients possibly because there is a commonality in the core functions regardless of make of router

What table? DHCP table? ARP table?
You talk about "lease". "Lease" only applies to DHCP addresses. If your address is not given by DHCP (=static), there is no lease and the DHCP table does not get populated.

EDIT: Just to add a bit more of technical details, for those interested.
What a 'router' does is simply 'routing' packets from one network to another, depending on the way it is set up. A router in itself doesn't have a hard limit (it can't because of how it works), but it can have performance issues if it is overused (in terms of CPU, RAM, etc.).
The most common tables on a router are the DHCP table, the ARP table and the routing table.
A DHCP table keeps track of all the addresses that the DHCP gives out to clients, each one of them with an expiring lease (unless the address is reserved). The number of addresses that it can use is limited and decided beforehand. *Normally*, a home router works on networks with 255 IP addresses each (minus a few reserved). Very rarely the DHCP uses ALL these addresses (for example, with default settings, it can go from a minimum of 50 to a maximum of 150, depending on the way it is set up).
If it runs out of addresses (DHCP table full), it simply won't give out any more addresses until some of the leases expire and those addresses become available again. Until then, a device can still connect to the network (either wireless or wired) by using a static, non-reserved address. The DHCP table won't do anything about that address (it doesn't care), the ARP table will take note of the MAC address and the corresponding IP address.

An ARP table is not in itself critical either. It simply stores useful information about MAC addresses and their IP addresses. If the table gets cleared (which normally happens when the router is rebooted), every time the router needs to find an IP address, it will send another request to the whole network (who has IP address 192.168.X.X? Tell the router at 192.168.1.1).

If we, for example, set our subnet mask to /22 we get 1022 addresses available.
Even if the DHCP server only offers 50 addresses, we can still connect as many devices as we want (up to the limit set by the subnet mask) with static addresses and it will all be part of the same network. The router has no knowledge of how many devices are out there, so it can't limit anything. The only time that it checks is when it needs to talk to them, otherwise, you can have as many as you want.