Cisco handset from home to office SIP/NAT/NAT/SIP

Have Asterisk running at work behind a Sonicwall firewall (VOIP and QoS optimizations builtin) and a Cisco 7960G with SIP v7.4 behind a Dlink home gateway at home.

Tried opening the TFTP (UDP 69) & SIP (UDP 5060-5061) ports at the firewall with NAT maps to Asterisk box at work and using the correct public IP addresses for the phone at home. Sonicwall’s VOIP connection monitor shows my handsets requests heading inbound at the firewall - but ultimately TFTP requests timeout on the phone when booting and no connection by voice to Asterisk in spite of the call appearance at the firewall.

Anyone done this or have some easy tips?

Thanks gang.