Doublecheck understanding of symmetric and restricted-latching

Hey folks,

 

I just want to doublecheck that I've understod the functions of latching properly, since I've got a customer scenario that acts very strange. (At least according to the customer ;-) )

 

The customer is connecting to our SBC for PSTN termination/interconnect, via their B2B.

 

This system does not change the RTP/IP-addresses of the SDP media, so here we get the private addresses of the customer network.

 

This tells me that I need symmetric-latching enabled, so that as soon as the customer generates any RTP, which is then NAT:ed, my SBC will latch onto the source ip/port of those RTP packets, and use the same for the return RTP traffic.