Dynamic IP Addresses

I

ITGuy

New Member
Hi,

Sorry if this is in the wrong forum, i have just done a search in this forum and not found anything relating to this topic, so if there is already one then sorry.

Anyway i need some help with dynamic ip addresses, with quite a few ISPs nowadays they issue there customers dynamic IPs instead of static IPs so therefore every connection that is made by a user can result in a different address.

What i need to know is, can say someone connect to the internet with an address of 82.209.109.23 and then later when there assigned another IP say 82.201.102.34, can the original IP that they were using (82.209.109.23) then be assigned to another computer user who is also using the same ISP? Or in other words are dynamic IPs shared or do they work in the same concept as static IPs, as in each computer has a unique address, the only difference being that dynamic IPs has several unique addresses? I hope that all makes sense, thanks in advance guys.
 
DHCP is assinged by a server for a period of time, called lease time. Now it is possible to assign the same ip to the same MAC address everytime if the server is set up that way. Typically it is not though because that would require a lot of extra work on the server admin's side capturing all the MAC addresses.

here is some good info on DHCP

http://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol

If you want to keep track of your dynamic IP there are third party services that allow this. One is dydns.org (www.dydns.org) and it can email you everytime your wan IP changes. This is handy for remote desktop and remote network connections away from home.
 
Hi tlarkin,

Thanks for your reply, but what i meant was generally can two different computers using the same ISP share a dynamic IP. I am an administrator for a messageboard forum site and we are having some problems with a possible troll user. This one user has several different IPs with one account which would lead me to believe they are using dynamic IPs, then we have several other accounts also using some of these IPs. So therefore is this the same person/computer or could it quite possibly be two or more people/computers using the same ISP and by considence sharing the range of assigned dynamic IPs?
 
what you would need is a router, b/c typically ISPs work differently. Sometimes they set a block of IPs to your account if you have multiple computers and you can pay a small extra nominal fee for more computers on their connection. other times they don't do that at all.

So, you will have one IP, which will be called your WAN IP from your ISP, and your router will basically act as a bridge and connects your internal network to your ISP.

for example your wan ip from your ISP might be 66.87.54.169 and your internal network IPs would be along the range of like 192.168.1.100 or what not.

Does that make sense?
 
Yes i understand that thanks, however would an ISP assign the same block of IPs to more than one of there customers, as in one of there customers in one house might a specific block of IPs could another person with the same ISP in a completely different house also use the same IPs or would they not be shared like this. I have searched other members IPs on our web site and the members that use dynamic IPs do not appear to share addresses with any other users registered on our site.
 
every ISP is different, however one ISP I had a while ago signed you a block of 5 IPs on their network but they didn't tell you that.

Anyways it is more secure to be behind a router and most ISPs require that now anyways and do not assign blocks. Your best bet is to ask your ISP. However they may charge an extra 5 dollars a month or what not for that extra IP.
 
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