Tools for diagnosing network problems

You can use the following commands and tools to diagnose network problems.

• ifconfig command: This command displays the assigned IP addresses, device names, bonding information and other information you might need during troubleshooting of networking issues.
• ping command: Use the ping command to test the connectivity of the network, testing both host names and IP addresses. Ping each host name on the network from every other host name to determine the status of network connectivity. If the ping command fails or hangs with host names, test with IP addresses. Ping each IP address on the network from every other IP address to determine network connectivity, first using internal IP addresses and then using corporate IP addresses. Test the connectivity between two host names or IP addresses in both directions, because a successful ping in one direction does not mean that the ping in the reverse direction will also succeed. Note that testing between two IP addresses on the same host does not aid in determining switch of cable issues, because the test never reaches beyond the network interface on the host.
• AIX® operating system commands:
  • errpt: This command displays all of the logged errors. Check for errors on network devices.
  • netstat -in: This command displays the status of all configured logical interfaces. Check that all of the logical interfaces that you expect to be available are displayed in the output. Non-zero or high counts in the Ierrs or Oerrs column might indicate that there is a problem with the logical interface associated with that value.
  • entstat -d device_name: This command displays the status of each Ethernet device driver and device statistics. Run this command for the physical network interface that corresponds to each logical network interface entry in the netstat output. For a port aggregation, run the entstat -d command on the aggregation name and not on the interfaces contained within the aggregation. Check for the high error or retransmit counts in the output (listed as "Transmit Errors" and "Packets Dropped").
• Network switch tools: For instructions on how to display counters of transmit errors, receive errors, and current link status, see the documentation for the network switch.
• Network load tools: Some network load tool can apply a heavy load to a network. For instructions on running the tool and interpreting the results, see the documentation for the network load tool you choose.