IP Conflict

I

irish614

New Member
Hey guys, I have 2 computers and a ps3 running off of my network right now, I put our old computer upstairs in my fathers room, I have one in my room and theres one downstairs ( the main computer that is hooked into the cable modem) After I set-up my fathers computer with internet a problem arose. The downstairs computer received a message saying "there is an IP conflict with the computers" and my fathers computer nor the main computer receive internet. I've heard about setting static IP's but I'm not sure how to do that. Anyway you guys could help? I am not understanding why 2 computers keep sharing the same IP address.
 
If you have a router it is acting as your DHCP server, reboot the machines in conflict until you resolve your IP conflict. If that does not help post back and we can take it to more further and more technical measures to fix it.

However, rebooting is the most simple way to fix an issue like this.
 
Yea thats what i have to keep doing, its weird it doesnt do it all the time it is kind of random, usually when my dad goes on his pc is when it starts.
 
reboot your router it probably has both machines on a different IP lease time which can sometimes screw it up. By reboot i mean unplug your router, count to 15 and plug the power back in.
 
DHCP will not issue out an ip that is already on the network, if i was you i would just set static ip's. First you need to record your dns server. go to start > run and type cmd, press enter. in the cmd box type ipconfig /all and jot down the following: Default Gateway and DNS servers.

Next; start > control panel > network connections. Right click on local area connection (the one that is connected if you have more than 1!) and click properties, scroll down the box and chose Internet Protocol (TCP/IP) double click it, click the "use the following ip address button" you must then enter a unique ip address on your subnet. so if your gateway is 192.168.1.1 then give it 192.168.1.150 for example, enter 255.255.255.0 for subnet mask, and enter the gateway and dns servers that you wrote down earlier.

Do the same for all the computers your using giving them a unique IP address.
 
Homenet said:
DHCP will not issue out an ip that is already on the network, if i was you i would just set static ip's. First you need to record your dns server. go to start > run and type cmd, press enter. in the cmd box type ipconfig /all and jot down the following: Default Gateway and DNS servers.

Next; start > control panel > network connections. Right click on local area connection (the one that is connected if you have more than 1!) and click properties, scroll down the box and chose Internet Protocol (TCP/IP) double click it, click the "use the following ip address button" you must then enter a unique ip address on your subnet. so if your gateway is 192.168.1.1 then give it 192.168.1.150 for example, enter 255.255.255.0 for subnet mask, and enter the gateway and dns servers that you wrote down earlier.

Do the same for all the computers your using giving them a unique IP address.
Click to expand...

DHCP will do all kinds of weird things. Default configuration is like this. It leases an IP to a client and then checks to see if that client is stil connected during the lease period. Once lease is up if still connected it issues the same IP. If two systems were issued the same IP but one was dormant and then tried to connect and was issued the same IP you get a conflict.

Remember a consumer router has 4 to 8 megs of memory so its not like its a super awesome DHCP service running there.

I say reboot the router. Its easy, takes a matter of seconds, and could fix the whole issue.

Or if you have two routers giving out IPs with different lease times. You do only have one router correct?
 
tlarkin said:
DHCP will do all kinds of weird things. Default configuration is like this. It leases an IP to a client and then checks to see if that client is stil connected during the lease period. Once lease is up if still connected it issues the same IP. If two systems were issued the same IP but one was dormant and then tried to connect and was issued the same IP you get a conflict.

Remember a consumer router has 4 to 8 megs of memory so its not like its a super awesome DHCP service running there.

I say reboot the router. Its easy, takes a matter of seconds, and could fix the whole issue.

Or if you have two routers giving out IPs with different lease times. You do only have one router correct?
Click to expand...

Interesting point, im assuming hes already tried rebooting the router, if not though then that might be an idea. the amount of memory used to hold a DHCP client table however is extremely small so its unlikely to be an issue. Also ive never come across a system offering DHCP that gave out a dupliate IP. When a DHCP discover is sent over broadcast and the server receives it, it checks the current DHCP clients table and lease periods first to ensure that it isnt giving one out that is already in use.
 
Homenet said:
Interesting point, im assuming hes already tried rebooting the router, if not though then that might be an idea. the amount of memory used to hold a DHCP client table however is extremely small so its unlikely to be an issue. Also ive never come across a system offering DHCP that gave out a dupliate IP. When a DHCP discover is sent over broadcast and the server receives it, it checks the current DHCP clients table and lease periods first to ensure that it isnt giving one out that is already in use.
Click to expand...

Routers also have other functions, NAT, SPI Firewall, routing, VLANs, QoS, port forwarding, encryption for wireless, ssh support, FTP, so on and so forth. So you are cramming all that into a 4 meg micro linux kernel. It can be done but its not going to be the greatest. You buy a cheap router it may use janky and buggy firmware, which could result in it dishing out the same IP.

Obviously you've never used a Microsoft product, otherwise you would have not used the word never:D
 
hehe, unfortunately I have to use Microsoft products daily, but I guess then ive just been very lucky thus far :D
 
hey guys, thanks for the responses. As for rebooting my router I've already tried that, I haven't tried setting up a static IP bc i wasnt too sure on how to do it. the router seems like it keeps resetting itself. I was just playing a game and got booted, i looked up and the CISCO Sytems light on the front of my linksys WRT54G router and it was not lit, once connection re-established it was orange again. Weird. So how do I go about creating static ip's? just make up the last few digits? like a 192.168.1.___ and fill the last in with whatever?
 
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Yep, just follow what I said above, you can just make the last number to be whatever you want (between 1 and 254 and make sure its not the same as your gateway which is prolly gonna be 1!) Any problems let me know.
 
quick question regarding the Linksys, when I set up static IP's do i have to change anything on the router configuration screen so that I will still read the computer's IP's or whatever or will they all be able to communicate to it still?
 
Hi, nope you wont have to change anything, just make sure that you set your default gateway as the ip of the router so that each machines knows where to send the traffic to.
 
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