Cisco SPA2102 Administration Manual page 44

Configuring Your System for ITSP Interoperability
Network Address Translation (NAT) and Voice over IP (VoIP)
STEP 3
STEP 4
STEP 5
Scroll down to the NAT Support Parameters section, and then enter the following
settings to support static mapping to your public IP address:
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Handle VIA received, Insert VIA received, Substitute VIA Addr: yes
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Handle VIA rport, Insert VIA rport, Send Resp To Src Port: yes
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EXT IP: Enter the public IP address for your router.
Click Voice tab > Line , where N represents the line interface number.
Scroll down to the NAT Settings section.
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NAT Mapping Enable: Choose YES.
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NAT Keep Alive Enable: Choose YES (optional).
Voice tab > SIP: NAT Support Parameters
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