Logstash not connecting elasticsearch? - http

Question

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.