View Full Version : Conflict between devices connected to the same router Ė Understanding IP addresses

05-21-2010, 09:47 AM

I have been using computers for a while now and I just realized that I donít know something as simple as IP addresses. Iím correctly connecting my Notebook, my iPhone and a PC laptop to the same routing (wirelessly) and a few times I have seen a message in my Notebook saying that another device is already using the same IP address, Iím assuming is my iPhone but to really find this out I would like to have a better understanding as to how IP addresses are assign to this devices when connected to a router, if Iím not mistaking each device should have its own unique IP address and if this is true how in the world these two devices are interfering with each other.

Can someone help me understand how IP addresses work? Something likeÖ

1- What is an IP address?
2- How routers communicate to clients?
3- Does the router assigns unique IP address to all devices connected to it, or it uses the device's IP to communicate?

Can someone be so kind and explain this a little bit or direct me to where I can find these basics.

Thanks a lot.

05-21-2010, 01:53 PM
What you're asking can be found in the on line Wikipedia and also from several other sites that have tutorials on networking. Makes for interesting reading. Start with Wikipedia (http://en.wikipedia.org/wiki/IP_address_allocation).


05-21-2010, 02:07 PM
Thanks a lot

05-21-2010, 11:58 PM
That wikipedia article is a harsh place to start.

For your home it depends on your setup but if your devices and router are setup for dhcp (dynamic host configuration protocol) then it works like this
Your router can assign a range of class C ip addresses - usually 192.168.(something).(something)
Your client needs to be setup for dhcp - to request ip configuration from the router
Your router assigns the ip address to the client as requested
Generally speaking - if you only have 1 router and normal clients there shouldn't be IP conflict as the router keeps track of who got assigned what number.

Usually conflict happens when you assign an ipaddress manually on the device.

There is a lot more going on behind the scenes and if you want to get into it look up OSI layers, TCP/IP, DHCP, Wifi Handshake, WPA Handshake to start.

Anyway - you must figure out where the conflict is coming from before you can start debugging. Go look at all your devices and inspect the ip address it think it has.

If you are running a wireless router - if someone is poaching, one way to poach is to assign an ip address manually and spoof your MAC address.

05-22-2010, 07:46 AM
Thanks a lot for the good advice!