Don't quote me but I think it depends on your service provider. BT openworld, for example, issues an IP address, but then every so often [I think it used to be every 5th time you logged on your pc] it allocates a different IP address. Others issue one IP address and it stays the same. - This may have changed as there may be security issues with an IP address being constant over a length of time. Perhaps a search on t'internet will answer your question.