When nagivating to Internet Calling->NAT Traversal, configuring the NAT traversal parameters and pressing the 'Apply" button will generate an error saying that no default SBC is selected Although the message is accurate in that indeed there are no default SBC selected, the generation of the NAT Traversal rules should not be predicated on it.

Expected rules:
SipXconfig must be able to generate nattraversalrules.xml complete with topology information borrowed from the Internet Calling page even when no 'default SBC' is selected.