[Freeswitch-users] external_sip_address and external_rtp_address Question

I only see one example for setting of external_sip_address and external_rtp_address tags. Is it true they are used to specify a SIP provider outside of a LAN (i.e. through a router)? If so, then can these tags be set for each sip_profile? So, if I have multiple external SIP providers that are accessed through NAT, they would each have their own external_sip_address and external_rtp_address? Best Regards, Jerry