Multi-boxing doesn't exist on this server. You are IP restricted to 1 account per server per IP for P99 & R99 (so you can play one character on P99 and one character on R99 concurrently, but not 2 accounts on the same server). If you have another real life person on the same IP as you, such as a roomate or spouse, apply for an IP exemption in the
Petitions & Exploit forum, following the
IP exemption request guidelines. Once you have an IP exemption, there are also repercussions for being caught multi-boxing.
TL;DR: Play 1 character at a time on P99/R99.