sir my question is that of a person have dynamic then it change when we restart our modem.
how forum caught multiple ids if our ip is dynamic.??
Thanks for your question staypk.
Having a Dynamic IP does not guarantee that you will have a different IP every time you log on to a site. In fact different ISP's use different methods in assigning Dynamic IP's.
Most Cable ISP's, at least in the United States, use Dynamic IP's for their residential customers but the IP rarely changes because it is assigned by the MAC address of the first device connected to the Cable Modem and the lease renews with the same IP until that MAC address changes. I use a Cable ISP at home and have had the same IP for 3 years.
Many Fiber Optic and DSL ISP's just us random IP's within a given block or set of blocks of IP addresses. Some of them even go so far as to rotate their clients IP's between 10-15 different IP's. They claim it is for client security but it is actually so the clients can't do any hosting of Game Servers or Web Servers.
My point in all of that is that your IP may change but may just rotate between the same group of IP's or remain on the same subnet giving the Forum a clue that you are using Multiple User Accounts.
If you are referring to our Forum blocking users that have Multiple User Accounts, we have many ways of cross checking User Names, Email Addresses and IP's including subnets. There are some other methods we use as well but I will not make them publicly known.