When using DSL or ISDN or Cable Internet, are you still using DHCP? I think so, because your IP# is not static. Someone explain

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I think ISP's lease an address and subnet it out to all their users/subscribers. It must be using a DHCP server depending on whose logged on to the network at what time. I use a cable modem and a router with DHCP built-in. When I configured the router, I put in the IP address from Winipcfg and it worked. When I restarted, it didn't because the IP address of my machine had changed. So, my thinking is that the ISP's DHCP Server assigns a dynamic IP address each time you logon. Hope this helps.

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I think this really depends on the ISP. Some will use DHCP to assign and rotate out IP addresses. This is most often for two reasons. First, to discourage you from running a server on your line. They will usually sell you static IPs or a higher class of service that include static IPs if you want to do this. The other reason is that IP addresses are not cheap and many times they will over-sell an area versus the number of IP address that they have there. Since they know that not everyone will be online at the same time all they need to do is lease the number of IP addresses that they need during average peak usage.

There are some providers that do not use DHCP but rather assign you an address with the caveat that it "can change" at any time based on their needs. I used to have DSL service like this from a local provider and my address didn't change for 2 years.

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I use a dsl and teh phone co gave me a USB modem. I wanted a ethernet modem. I brought my own modem and setting up my router I caled the phone Co and the told the IP address I use is dynamic and if I wanted a static I could pay 5 dollars extra. I would think that most ISPs would use the dynamic Ip unless you pay extra. Regarless if it is Dynamic aslong as you dont break connection with the ISP the IP address wont change.
Dont know if this help are not I just relayed the ISPs response to me
George

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First -
I am in total agreement with all previous postings on this subject. There are many reasons for ISP's not assigning static IP's to customers.
Second -
One of the major reasons for an ISP not to assign a static IP to a customer is security. The ISP's server is secure. But they have no way of controlling the security of their customers systems. And an always on Static IP can open up a security can of works for the ISP if the security is lacking on the customer's computer. Think about it - how many users actually implement & enforce a ,rigid security design, have the latest patches installed, have unused ports locked down, etc......

Third -
Having worked for a small ISP, ALL of our security breaches were due to & came through some small business or customer that just had to have a static IP leaving doors open on their servers. [ Security Design - Or lack of ]

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I must be one of those rare cases. My IP has been the same for the past 2.5 years or so. As long as you have a dedicated connection, my ISP doesn't care what kind of servers you host. Guess I just got lucky.

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My ISP uses dynamic IP addressing with a 24 hour lease. But because I have a cable router that is permanently on I've had the same IP address for about 4 months.

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