Logstash not connecting elasticsearch?

I am running ELK setup on a single machine. Everything was working fine
untill I switched off my internet connection.

My logstash console shows this error when I switch off Internet connection:

log4j, [2014-11-27T10:31:57.480]  WARN: 

org.elasticsearch.transport.netty: [logstash-HP-Pro] exception caught on
transport layer [[id: 0x7a124750]], closing connection
java.net.SocketException: Network is unreachable
at sun.nio.ch.Net.connect0(Native Method)
at sun.nio.ch.Net.connect(Net.java:465)
at sun.nio.ch.Net.connect(Net.java:457)
at sun.nio.ch.SocketChannelImpl.connect(SocketChannelImpl.java:670)
at
org.elasticsearch.common.netty.channel.socket.nio.NioClientSocketPipelineSink.connect(NioClientSocketPipelineSink.java:108)
at
org.elasticsearch.common.netty.channel.socket.nio.NioClientSocketPipelineSink.eventSunk(NioClientSocketPipelineSink.java:70)
at
org.elasticsearch.common.netty.channel.DefaultChannelPipeline.sendDownstream(DefaultChannelPipeline.java:574)
at
org.elasticsearch.common.netty.channel.Channels.connect(Channels.java:634)
at
org.elasticsearch.common.netty.channel.AbstractChannel.connect(AbstractChannel.java:207)
at
org.elasticsearch.common.netty.bootstrap.ClientBootstrap.connect(ClientBootstrap.java:229)
at
org.elasticsearch.common.netty.bootstrap.ClientBootstrap.connect(ClientBootstrap.java:182)
at
org.elasticsearch.transport.netty.NettyTransport.connectToChannels(NettyTransport.java:705)
at
org.elasticsearch.transport.netty.NettyTransport.connectToNode(NettyTransport.java:647)
at
org.elasticsearch.transport.netty.NettyTransport.connectToNode(NettyTransport.java:615)
at
org.elasticsearch.transport.TransportService.connectToNode(TransportService.java:129)
at
org.elasticsearch.discovery.zen.ZenDiscovery.innerJoinCluster(ZenDiscovery.java:338)
at
org.elasticsearch.discovery.zen.ZenDiscovery.access$500(ZenDiscovery.java:79)
at
org.elasticsearch.discovery.zen.ZenDiscovery$1.run(ZenDiscovery.java:286)
at
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:744)

EDIT

Logstash output config:

output {

        elasticsearch { host => localhost }
        stdout { codec => rubydebug }
}

So it seams it's unable to connect to ES server.

So is an internet connection be required always?? I am new to the setup.

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