Network connectivity issues can be pretty noisy in Puppet. The agent in the following code sample does not have the ability to talk to the master, due to either a bad networking route or a firewall stopping traffic to our Puppet Master. In the following example, a firewall is blocking the agent from connecting to the master:

[root@wordpress ~]# puppet agent -t
Warning: Unable to fetch my node definition, but the agent run will continue:
Warning: Failed to open TCP connection to pe-puppet-master:8140 (No route to host - connect(2) for "pe-puppet-master" port 8140)
Info: Retrieving pluginfacts
Error: /File[/opt/puppetlabs/puppet/cache/facts.d]: Failed to generate additional resources using 'eval_generate': Failed to open TCP connection to pe-puppet-master:8140 (No route to host - connect(2) for "pe-puppet-master" port 8140)
Error: /File[/opt/puppetlabs/puppet/cache/facts.d]: Could not evaluate: Could not retrieve file metadata for puppet:///pluginfacts: Failed to open TCP connection to pe-puppet-master:8140 (No route to host - connect(2) for "pe-puppet-master" port 8140)
Info: Retrieving plugin
Error: /File[/opt/puppetlabs/puppet/cache/lib]: Failed to generate additional resources using 'eval_generate': Failed to open TCP connection to pe-puppet-master:8140 (No route to host - connect(2) for "pe-puppet-master" port 8140)
Error: /File[/opt/puppetlabs/puppet/cache/lib]: Could not evaluate: Could not retrieve file metadata for puppet:///plugins: Failed to open TCP connection to pe-puppet-master:8140 (No route to host - connect(2) for "pe-puppet-master" port 8140)
Info: Loading facts
Error: Could not retrieve catalog from remote server: Failed to open TCP connection to pe-puppet-master:8140 (No route to host - connect(2) for "pe-puppet-master" port 8140)
Warning: Not using cache on failed catalog
Error: Could not retrieve catalog; skipping run
Error: Could not send report: Failed to open TCP connection to pe-puppet-master:8140 (No route to host - connect(2) for "pe-puppet-master" port 8140)

You may notice recurring themes in the preceding examples: No route to host and Failed to open TCP Connection. Each component of our catalog compilation will individually print a message back, alerting us to a connection failure. When we see no route to the host, we know that a firewall is between our agent and master, or that there is no network route to the host. This can also be caused by an improper DNS or /etc/hosts entry on the agent attempting to connect to the master.