[asterisk-users] Remote SIP extensions with no dial tone

[james daes]

have Asterisk installed and all SIP extentions are working inside the NAT,
however, when I try connecting from external SIP phones, i hear no dial
tone.
sip.conf is as follows
externip = dedra.dyndns.org
localnet=192.168.0.0/255.255.255.0
nat=yes

am I doing anything wrong?  Please assist. I am using Grandstream sip
phones.
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