Public IP often change, is that normal?

Two or three hours is a little more frequent than normal, but is not unheard of. The public addresses are managed by your ISP and do not affect your internal addresses, which are managed by your router and are quite separate.

If you rely on somebody having access to your public address because you are running a web or games server, then you should check out Dynamic DNS services such as dyn.com or noip.com (there are others). This will give you a fixed URL that points to your current IP address. Some routers handle these directly, while other routers do not and you require a small utility running on your server to update the DDNS service with each change of IP address.

You probably did not notice it, but each time your address changes, you are probably disconnected from the Internet for around 30 seconds. Even if your are streaming movies, your devices will probably buffer sufficient data for the break not to be apparent.

I hope this helps.

the answer is absolutely yes.

There are ways around it, but for most common usage, the fact that your IP might change from time to time isn't an issue.

IP addresses are divided into two types: static and dynamic. Static IP addresses do not change, and dynamic addresses do.

Static IP addresses are used when you need to make sure that the same service is available at the same IP address for a long time. For example the IP address to which "ask-leo.com" resolves is static. Unless manually changed, that IP address is always assigned to the specific server that hosts this site.

Dynamic IP addresses are used when you don't, or rarely, need to initiate a connection to your computer from somewhere else. For example almost all the connections you make using a home computer are outbound; you are initiating a connection to a server somewhere else. You probably never attempt to access your computer from a remote location, so you don't need to know or care what your IP address is. The fact that it might change doesn't break anything.

Wow no attention to detail..

he stated "When connect to internet, my ISP assign me and internal ip (10.x.x.x)

I use whatismyipaddress.com to check the public IP, and I find that this public IP often change (it change every 2 or 3 hours and I didn't disconnect/reconnect from internet during that period), and the internal IP stay the same. Is this normal?" His local Ip didn't change just his public one did.

Unless you are hosting some sort of server it shouldn't be an issue.

Your public IP can be found at:

http://www.whatismyip.com/

Any 10.x.x.x is not a public IP address, that address range is non-routable, no one on the Internet can access those IP addresses. There is no way the "what is my IP" apps would return a 10.x.x.x address unless the ISP is deliberately hiding their public IP from their customers. (re-directing public IP queries)

Your ISP may be assigning that IP to your WAN service, but that means farther into the ISP's network, there is a public IP. But, that also means you cannot do any port forwarding since you may not have access to the router.

It is normal if your ISP is using dynamic rather than static IP addresses. With a static address you are assigned a number and keep it permanently. With dynamic the ISP as a pool of addresses and each time you access the Internet you are assigned a number to use, Once you are finished, the number returned to the pool. Since it would be unusual for every customer of an ISP to be on line at this same time, this allows the ISP to serve a large numbers of customers with a smaller number of addresses, thus reducing the cost to the ISP.

Your IP address is assigned via a protocol called DHCP, where DHCP uses a "lease" concept. When the lease timer expires the IP Address is renewed.

You're public IP Address CAN NOT be 10.x.x.x. 10.x.x.x and 192.168.x.x domains are not routable on the Internet. Those addresses are reserved. You're not doing something right.

Its probably normal, you may have a dynamic IP address. Dont worry about it, it actually makes it harder for some types of malware to attack your computer :)

If you are concerned contact your ISP.