Connection issue with a slave node

Hi,
I have two nodes cluster which was working fine for about 3 weeks, until today. A data node refuses to connect to the master node with this error. I can ping either node and the data seems intact, but they just cannot talk to each other. Does anyone know how to fix this? Thanks!!

[2016-03-24 23:59:04,828][WARN ][shield.transport.netty ] [node-2] exception caught on transport layer [[id: 0xdc15a179]], closing connection
java.net.NoRouteToHostException: No route to host
at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method)
at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:717)
at org.jboss.netty.channel.socket.nio.NioClientBoss.connect(NioClientBoss.java:152)
at org.jboss.netty.channel.socket.nio.NioClientBoss.processSelectedKeys(NioClientBoss.java:105)
at org.jboss.netty.channel.socket.nio.NioClientBoss.process(NioClientBoss.java:79)
at org.jboss.netty.channel.socket.nio.AbstractNioSelector.run(AbstractNioSelector.java:337)
at org.jboss.netty.channel.socket.nio.NioClientBoss.run(NioClientBoss.java:42)
at org.jboss.netty.util.ThreadRenamingRunnable.run(ThreadRenamingRunnable.java:108)
at org.jboss.netty.util.internal.DeadLockProofWorker$1.run(DeadLockProofWorker.java:42)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)