[looptest]
exten => _X.,1,Set(i=${SIP_HEADER(x_loopback_test)})
exten => _X.,n,GotoIf($[ ${i} >= 5 ]?answer:iterate)
exten => _X.,n(iterate),Verbose(Set(i=$[ ${i} + 1 ]))
exten => _X.,n,Set(i=$[ ${i} + 1 ])
exten => _X.,n,SipAddHeader(X-Loopback-Test: ${i})
exten => _X.,n,Dial(SIP/looptest/${EXTEN})
exten => _X.,n(answer),Answer
exten => _X.,n,Echo