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I've got a Cisco Linksys X3500 ADSL2+ router which we have been using fine for a long while, until all of a sudden, the router stopped providing IP addresses after a certain amount of clients were connected to the network. The only way I can connect another client to the network is by removing another device. Manually setting an IP address for the new client does not work.

I haven't really changed any settings, apart from the WiFi configuration, but the issue is still present over Ethernet, and the problem is present on all computers, regardless of operating system.

I've tried modifying the IP address range, but to no avail. Strangely enough, however, the IP addresses provided by the dhcp server have huge differences between them (for example, the lowest IP ends in .9, whilst the next lowest ends in .26 – I don't think that's normal).

Any clues to how I can solve this? I'm on the latest firmware. Thanks in advance.

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Page 187 of the X3500 manual shows how to extend the range of the DHCP server. Generally speaking, you might want to extend the subnet of your DHCPs range. What does your configuration look like? How many clients do you actually have on your network?

Since the manual says that 192.168.1.1 is the default IP adress of the router, take the following example on how your network might be configured:

wider netmask.

This will net you 1022 total available IPs for DHCP. Furthermore, you might try to reduce the DHCP lease time. This will make your router reassign IPs faster.

  • My router doesn't offer that subnet mask, however, I have selected another subnet mask and the max clients has reduced to 50. I'll try and see how it goes, and I will select this as the answer if everything works fine. Right now I don't have a lot of devices on to test. Thanks anyway! – georgeunix Jan 13 '15 at 15:45
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The router maintains a pool of IP-adresses to provide over DHCP. When that pool is exhausted, you need a device to return its IP-address to the pool before another one can be serviced.

Some routers can be reconfigured to provide more addresses. This is highly vendor dependent, but usually is done using a web browser. Details are typically printed on the device itself.

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Are you sure you (or someone else) didnt change anything on the router? It sounds like someone changed settings on the DHCP server built into the router. It sounds like DHCP leases arent being released. If you havent done any special configurations on your router, you might consider doing a factory reset. This would return the router and its settings to its default state - which should return everything to normal. If you are comfortable you can go into the DHCP server settings and see if something looks awry, especially in the lease settings.

  • While it's a great idea that IPs might not get released, I'd suggest to reboot the router first. I had this problem before with linksys gear and a reboot indeed helped. – Patrick R. Jan 12 '15 at 19:25
  • If I can't get @PatrickR. 's method to work, then I'll back up the configuration and factory reset the router. Thanks! – georgeunix Jan 13 '15 at 15:48
  • Same issue -- same number of clients allowed at any one time. – georgeunix Jan 13 '15 at 16:13
  • The router still gives out sparse IP addresses. – georgeunix Jan 13 '15 at 16:14

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