A-MQ 6.2 with duplex network connector: logs show repeated disconnection and reconnection

Issue

An A-MQ 6.2 message broker is configured with a duplex network connector to forward messages to, and consume from, another broker. The configuration of the upstream broker will take this form in activemq.xml:

<networkConnectors>
        <networkConnector name="something" duplex="true" uri="static:(tcp://192.168.1.51:61616)" userName="something"  password="something">
        </networkConnector>
</networkConnectors>

The connector works, but the network connector is disconnected and reconnected every three minutes. In the log of the downstream broker are entries like this:

10:15:03,658 | INFO  | vice[amq] Task-5 | DemandForwardingBridgeSupport    | 184 - org.apache.activemq.activemq-osgi - 5.11.0.redhat-620133 | amq bridge to amq stopped
10:15:03,719 | INFO  | .114:52627@61616 | TransportConnector               | 184 - org.apache.activemq.activemq-osgi - 5.11.0.redhat-620133 | Connector vm://amq started
10:15:03,720 | INFO  | .114:52627@61616 | TransportConnection              | 184 - org.apache.activemq.activemq-osgi - 5.11.0.redhat-620133 | Started responder end of duplex bridge test@ID:localhost.localdomain-60971-1439284472297-0:1
10:15:03,732 | INFO  | oker= vm://amq#4 | DemandForwardingBridgeSupport    | 184 - org.apache.activemq.activemq-osgi - 5.11.0.redhat-620133 | Network connection between vm://amq#4 and tcp:///192.168.1.114:52627@61616 (amq) has been established.
10:15:33,722 | WARN  | tyMonitor Worker | DemandForwardingBridgeSupport    | 184 - org.apache.activemq.activemq-osgi - 5.11.0.redhat-620133 | Network connection between vm://amq#4 and tcp:///192.168.1.114:52627@61616 shutdown due to a remote error: org.apache.activemq.transport.InactivityIOException: Channel was inactive for too (>30000) long: tcp://192.168.1.114:52627
10:15:33,729 | INFO  | vice[amq] Task-8 | TransportConnector               | 184 - org.apache.activemq.activemq-osgi - 5.11.0.redhat-620133 | Connector vm://amq stopped
10:15:33,730 | INFO  | vice[amq] Task-8 | DemandForwardingBridgeSupport    | 184 - org.apache.activemq.activemq-osgi - 5.11.0.redhat-620133 | amq bridge to amq stopped
10:15:33,781 | INFO  | .114:52628@61616 | TransportConnector               | 184 - org.apache.activemq.activemq-osgi - 5.11.0.redhat-620133 | Connector vm://amq started