hi im sarah umm how do i

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evelmunkey said:
Most cable companies assign a 24 hour lease to your ip address and is renewed only if your cable modem is connected when the lease expires. So if you left the modem off for more than their lease (24 hrs), you would change your IP address when the modem is restarted. I am not sure if all companies work this way but the three I have been with have always done it and the lease time is always 24 hrs.

The leases are usually far less, but it all depends on how the DHCP servers are configured.

Generally unplugging your modem for 5 minutes will give you a new IP
 
No way, just unplugging it will not work. Why dont all of you try it and let me know. I did it and my ip is the same. The only time mine ever changed was during last years hurricane season when power was out for two days.
 
evelmunkey said:
No way, just unplugging it will not work. Why dont all of you try it and let me know. I did it and my ip is the same. The only time mine ever changed was during last years hurricane season when power was out for two days.

As I said it all depends on how the DHCP servers are setup.

As well as how your own router is setup.

When you connect this is what can happen and why you stay on the same IP alot of the time

YOU: Hey DHCP server I need an IP
DHCP: Take this one
YOU: I dont want this one, I wanted the one I had 5 minutes ago
DHCP: Okay fine take the one you had 5 minutes ago.

This is what can happen when you have just disconnected and not released. In some routers you can send a release and than a renew.

I know alot about DHCP and setting it up on cisco equipment, as I setup DHCP servers on cisco equipment. And your ISP is likely using Cisco.
 
No, that is not how it works. The client will usually accept the first IP address offered. The DHCP server will have a table that assigns an IP address to a MAC address for XX amount of time. If you are connected at that time, the DHCP server will renew your lease. If you are not connected and the alloted time (lease) has passed, the IP address is relased back into the address pool. When you hook your stuff back up, your MAC address doesnt have a leased IP so it would pull from the pool of IP addresses. The chances of getting the last one is very slim.

If you doubt me, try it out.

Also, here is great link that explains the cycle. I have worked with cisco and it works the same. Most companies I have dealt with use windows server for DHCP because it much easier to use.

http://tinyurl.com/asqce
 
When windows has a disconnect and than connects again it will try to get the same IP address it had before.

DHCP on IOS 12.2 will sometimes try to assign a different IP address depending on the situation.
 
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