In my case this happens when the Cisco VPN software is active. I suspect that the traffic is being routed through the VPN adapter. /var/log/system.log says when I initiate a call:
Oct 22 08:43:09 Hyperion kernel[0]: utun_ctl_connect: creating interface utun3
Oct 22 08:43:09 Hyperion kernel[0]: utun3: attached with 0 suspended link-layer multicast membership(s)
Oct 22 08:43:09 Hyperion.local acvpnagent[5452]: Function: getInterfaces File: ../../vpn/Common/Utility/NetInterface_unix.cpp Line: 1330 missing PPP destination address for interface "utun0". Check profile PPPExclusion (set to Automatic?) or contact your administrator.
Oct 22 08:43:09 --- last message repeated 1 time ---
Oct 22 08:43:09 Hyperion.local acvpnagent[5452]: Function: getInterfaces File: ../../vpn/Common/Utility/NetInterface_unix.cpp Line: 1330 missing PPP destination address for interface "utun1". Check profile PPPExclusion (set to Automatic?) or contact your administrator.
Oct 22 08:43:09 Hyperion.local acvpnagent[5452]: Function: getInterfaces File: ../../vpn/Common/Utility/NetInterface_unix.cpp Line: 1330 missing PPP destination address for interface "utun3". Check profile PPPExclusion (set to Automatic?) or contact your administrator.
Oct 22 08:43:09 Hyperion.local wirelessproxd[55]: UUID is invalid and unconnectable. Failed to connect to peer: <__NSConcreteUUID 0x7fb72aa05dd0> 2C344049-B6EF-43DE-968E-9F1D30A01587
Oct 22 08:43:09 Hyperion.local acvpnagent[5452]: A routing table change notification has been received. Starting automatic correction of the routing table.
Oct 22 08:43:09 Hyperion.local acvpnagent[5452]: Function: getInterfaces File: ../../vpn/Common/Utility/NetInterface_unix.cpp Line: 1330 missing PPP destination address for interface "utun0". Check profile PPPExclusion (set to Automatic?) or contact your administrator.
Oct 22 08:43:09 --- last message repeated 1 time ---