(Lo siento por el recorte, pero es que el editor, hoy está demasiado cabezón, y ni con "código" funciona):
Yo uso una configuración muy simple, para llamar a otros usuarios SIP de Betamax/Dellmont:
Con esto, marcando #4#, conecta con el usuario "curro999" en Betamax (no soy yo):
(Cargando foto desde OhNO!, puede tardar un poco, sé paciente...)
Por aquí comentaban algo de eso, aunque se referían a marcar una IP, no un nombre de dominio Sip: fredshack.com/docs/linksys_3102.html
How to make direct IP calls with a Linksys 3102?
GrandStream : "Note:- You will need to have SIP Server field blank, along with NAT traversal set to NO, no STUN Server configured and Use Random Ports set to NO. You can make calls between public IPs and Private IPs under the same LAN." (link roto)
... so as to avoid using an SIP PBX, and just have the Linksys ring a remote IP phone through the Net when a PSTN call comes in?
Enable IP Dialing Enable IP Dialing no
Note: If IP dialing is enabled, one can dial [user-id@]a.b.c.d[:port], where "@", ".", and ":" are dialed by entering "*", user-id must be numeric (like a phone number) and a, b, c, d must be between 0 and 255, and port must be larger than 255. If port is not given, 5060 is used. Port and User-Id are optional. If the user-id portion matches a pattern in the dial plan, then it is interpreted as a regular phone number according to the dial plan. The INVITE message, however, is still sent to the outbound proxy if it is enabled.
Ya nos contarás qué has hecho.. xDD