how to test router firewall for SIP chat or voice calls?

I can send and receive SIP chat on the local network between an Ekiga account on a Jitsi softphone and a getonsip account on csip-simple on an android tablet using this router:

Hardware Version WNR1000v2 
Firmware VersionV1.1.2.54NA 
GUI Language VersionV1.0.0.110 
Operation ModeRouter 
LAN Port 
MAC AddressC0:3F:0E:8B:4D:04 
IP Address192.168.1.1 DHCP ServerOn


MAC Address <omitted>
IP Address <omitted> 
Connection DHCP 
IP Subnet Mask 255.255.255.192
Domain Name Server
8.8.8.8
8.8.4.4
208.67.222.222

However, calls are just dropped. Is it the router? How would I know? Presumably, chat and voice use the same ports/etc with regards to SIP and router firewalls?

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