Checking the TCP/IP subsystem

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You can investigate the TCP/IP subsystem using AIX® commands.

These commands include the following:

  • Use the netstat command to make sure that the network interfaces are initialized and that a communication path exists between the local node and the target node.
  • Use the ping command to check the point-to-point connectivity between nodes.
  • Use the ifconfig command on all network interfaces to detect bad IP addresses, incorrect subnet masks, and improper broadcast addresses.
  • Scan the /var/hacmp/log/hacmp.out file to confirm that the /etc/rc.net script has run successfully. Look for a zero exit status.
  • If IP address takeover is enabled, confirm that the /etc/rc.net script has run and that the service interface is on its service address and not on its base (boot) address.
  • Use the lssrc -g tcpip command to make sure that the inetd daemon is running.
  • Use the lssrc -g portmap command to make sure that the portmapper daemon is running.
  • Use the arp command to make sure that the cluster nodes are not using the same IP or hardware address.
  • Use the netstat command to:
    • Show the status of the network interfaces defined for a node.
    • Determine whether a route from the local node to the target node is defined.

      The netstat -in command displays a list of all initialized interfaces for the node, along with the network to which that interface connects and its IP address. You can use this command to determine whether the service and boot interfaces are on separate subnets. The subnets are displayed in the Network column.

netstat -in

Name Mtu NetworkAddress  IpktsIerrs  OpktsOerrsColl
lo0 1536 <Link> 18406  0 18406  00
lo0 1536 127 127.0.0.118406  0 18406  00
en1 1500 <Link> 11116260 58643  00
en1 1500 100.100.86.100.100.86.136  11116260 58643  00
en0 1500 <Link> 943656 0 52208  00
en0 1500 100.100.83.100.100.83.136  943656 0 52208  00
tr1 1492 <Link> 18790 165600
tr1 1492 100.100.84.100.100.84.136  18790 165600

Look at the first, third, and fourth columns of the output. The Name column lists all the interfaces defined and available on this node. Note that an asterisk preceding a name indicates the interface is down (not ready for use). The Network column identifies the network to which the interface is connected (its subnet). The Address column identifies the IP address assigned to the node.

The netstat -rn command indicates whether a route to the target node is defined. To see all the defined routes, enter:

netstat -rn

Information similar to that shown in the following example is displayed:

Routing tables
DestinationGateway  Flags  Refcnt UseInterface
Netmasks:
(root node)
(0)0 
(0)0 ff00 0 
(0)0 ffff 0 
(0)0 ffff ff80 0  
(0)0 70 204 1 0
(root node)Route Tree for Protocol Family 2:
(root node)
127 127.0.0.1U 3  1436  lo0
127.0.0.1 127.0.0.1UH0456  lo0
100.100.83.128100.100.83.136  U 6 18243  en0
100.100.84.128100.100.84.136  U 1  1718  tr1
100.100.85.128100.100.85.136  U 2  1721  tr0
100.100.86.128100.100.86.136  U 8 21648  en1
100.100.100.128  100.100.100.136 U 039  en0
(root node)Route Tree for Protocol Family 6:
(root node)
(root node)

To test for a specific route to a network (for example 100.100.83), enter:

netstat -nr | grep '100\.100\.83'

100.100.83.128100.100.83.136  U 6 18243  en0

The same test, run on a system that does not have this route in its routing table, returns no response. If the service and boot interfaces are separated by a bridge, router, or hub and you experience problems communicating with network devices, the devices may not be set to handle two network segments as one physical network. Try testing the devices independent of the configuration, or contact your system administrator for assistance.

Note that if you have only one interface active on a network, the Cluster Manager will not generate a failure event for that interface.

See the netstat man page for more information on using this command.