Could you please tell us what have you tried so far ?
Have you seen the execution plan to check if your index was in fact being used ?
An index on (ip_from,ip_to) will for sure help, but I guess you already tried this.
Your best index option will be to create a clustered index on the ip_from and ip_to fields.
If your primary key is clustered (which it is by default) you will need to change the primary key to a nonclustered index first then you can create a new clustered index.
If you want to use a nonclustered index then create the index on the same fields ip_from and ip_to, and add any other columns which you need returned as included columns in the index. Then only return these columns. It is best to not return return any columns which you do not need.