Yeah you can still use your old no-ip
Go to your repack the open up "MaNGOS" then "realmd" go down to the bottom of the file and put your ip at "BindIP"
LoginDatabaseInfo = "127.0.0.1;3306;root;ascent;realmd"
LogsDir = ""
MaxPingTime = 30
RealmServerPort = 3724
BindIP = "here should your No-ip be"
PidFile = ""
LogLevel = 0
LogTime = 0
LogFile = "Realmd.log"
LogTimestamp = 0
LogFileLevel = 0
LogColors = ""
UseProcessors = 0
ProcessPriority = 1
RealmsStateUpdateDelay = 20
WrongPass.MaxCount = 0
WrongPass.BanTime = 600
WrongPass.BanType = 0