why wouldn't your computer renew it's ip address on it's own?

Answer 1

It depends on a lot of things, mainly where the PC is getting its IP address.

If you are at work, you're probably getting it from a DHCP server.

If you have an internet router, you are probably getting it through DHCP from the router.

If you are talking about your internet IP, then it's coming from your ISP.

If your IP is fixed, then it will never renew.

This is how it works with DHCP. When you first turn on your PC, it does a broadcast over the network requesting an IP address.

If there is a DHCP server available (either from the domain, router, or ISP) the DHCP server will respond with an IP address and tell the PC, "Use this IP address... it's good for 'x' days"

The 'x' days is called the "lease time". Most DHCP servers default at 8 days but it can be set to anything.

Now, when 1/2 of that lease time has gone by, your PC will begin sending out requests to renew that lease. If the IP address is still available, then the PC will continue to use the same IP for another 'x' days.

So, even if the lease is '8' days, it will renew every 4 days.

If the 8 days goes by and it hasn't been renewed (say if a laptop has been disconnected from the network), the DHCP server MIGHT give that IP address to someone else.

That's basically how it works.

The only way it won't renew an IP address is if...

1) The PC cannot contact the DHCP server. (Server went down? Router has DHCP disabled? PC no longer has a connection to the DHCP server? Bad hub/switch? Bad cable?)

2) The PC has DHCP turned off. (Such as a static IP address. If the PC is set to "Obtain Automatically", then it is turned on.)

3) There are no more IP addresses available. (Granted, this is rare but I've seen it happen! If your subnet only has say 8 IP addresses available, and you plug in 9, one of them won't get an IP.)

There are many reasons it might not renew. Hopefully I've given you enough information to begin to track down the problem.

Answer 2

ip addresses are given by dhcp servers. you can set when the ip expires on your dhcp server. if you set it to less than 1 minute, then you should get the desired effect.