While setting up Lync, I found that I was unable to place any voice calls.  I fired up event viewer, and saw the following errors:

Response Data:
101  Progress Report
ms-diagnostics:  12006;reason="Trying next hop";source="mycomputer.mydomain.local";PhoneUsage="Outoing";PhoneRoute="Outgoing";Gateway="123.234.1234.234";appName="OutboundRouting"

504  Server time-out
ms-diagnostics:  1038;reason="Failed to connect to a peer server";WinsockFailureCode="10061(WSAECONNREFUSED)";WinsockFailureDescription="The peer actively refused the connection attempt";Peer="mycomputer.mydomain.local";Port="5070";source="mycomputer.mydomain.local";OriginalPresenceState="0";CurrentPresenceState="0";MeInsideUser="Yes";ConversationInitiatedBy="0";SourceNetwork="0";RemotePartyCanDoIM="No"

After doing some searching, I found that the reference to Port="5070" usually points to issues with the mediation server.  So I opened up services and it turns out I had never installed the mediation service role.  Once installing the mediation server role and starting the service, the errors vanished!