Sip and sip phone

how to prevent same username used on multiple sip phone asterisk?

That is a human factors question, not a technology one.

Posible solution: … -deny-mask

i have two system and config their sip phone with same user name. both of them registered but in sip buddies table, ip address field set with second system’ ip. i want to prevent this . i dont want to limit SIP traffic to and from this peer to a certain IP or network