Asterisk Console when phone 273 calls phone 272

 -- Executing Dial("SIP/001759E558FE01-26d1", "SIP/272") in new stack
Apr 27 10:16:43 WARNING[3396]: chan_sip.c:1973 create_addr: No such host: 272
Apr 27 10:16:43 NOTICE[3396]: app_dial.c:1029 dial_exec_full: Unable to create channel of type 'SIP' (cause 3 - No route to destination)
  == Everyone is busy/congested at this time (1:0/0/1)
  == Auto fallthrough, channel 'SIP/001759E558FE01-26d1' status is 'CHANUNAVAIL'

Extensions.conf
exten => 272,1,Dial(SIP/272)