I've noticed a few people having trouble with IP bans, but I'm sure most of them already have found their ways around it.
For the ones in need of help, I shall try my best to do what I can.
Just a side note, if you're hosting a MineCraft server or something where you've given another your full IP, this will effect that IP others connect on.
With an IP ban the address of your router/modem is blocked from communicating with its destination. There is more than one way to work around this, but I'm going to show you a very simple way.
If you've ever noticed after a power outage, when you log back onto Vindictus you get the 10 minute warning because of an IP change,

that means your router has a Dynamic IP setting enabled, this is very good and skips, everything all the way down to MAC Spoofing.
If not, have no fear! here's that you do.

From here, you'll get a large list of things, what you're looking for is something that starts with "192.168..."

Next, we open our web browser, in the address bar we put the "Modem/Router's" local IP we've just found with "ipconfig".

At this point you're a bit on your own, in most cases your modem/router will have a default username and password, you'll either need to go google and search "router passwords" (should be first link) and look for the brand name or your router/modem, or if none work, ask the person who may have put a custom password on it.

If you cannot log into the router, you can always use a proxy method, but I wont be going into that in this tutorial.
Next we come to our Router's home page, you'll need to look up a user manual for your router, then look for IP settings.
I can't help much here because it different for every brand.
This is what mine looks like, yours may be different.

After you've selected Dynamic IP setting, restart your router/modem and your IP will have changed.
MAC Spoofing.
There is another way that they use along side IP bans, this is called a MAC address ban.
I like to use a program call SMAC, but I'd recommend Technitium MAC Address Changer because it's freeware, so you don't need to buy it from thepiratebay.
Download and install Technitium MAC Address Changer, after you've installed the program open it.

After you've clicked "Change Now!" you may need to restart your computer/reset your computers network adapter (restarting is easier).
Welp, that does it, I hope I helped some who were having trouble with this, let me know if there's anything you think should be added.