Troubleshooting for z/OS networking issues

Table 1. z/OS networking issues . Troubleshooting z/OS® networking issues
Symptom General z/OS networking configuration errors
Problem Determination
  • Check syslog (z/OS console messages) for errors during the start of TCP/IP or VTAM®.
  • Validate configuration files match for device numbers and names in the device map, VTAM definitions, and TCP/IP configuration profile. Specifically, follow the definitions to ensure that the tunnel and external addresses in the device map are defined through VTAM and TCP/IP to be the correct device names and addresses in z/OS. These configuration errors can be tricky because device names in the TCP/IP profile are arbitrary.
Symptom Unable to establish a network tunnel on a 10.x.x.x network.
Problem Determination On a 10.x.x.x network, you can establish the tunnel by configuring the tunnel to be on a 192.168.1.x address. For example, configure the tunnel device in the devmap as: 
name awsosa 0009 --path=A0 
      --pathtype=OSD 
      --tunnel_intf=y 
      --tunnel_ip=192.168.1.1
Configure z/OS TCP IP profile as a tunnel IP of 
192.168.1.2 netmask 255.255.255.0
Symptom Cannot connect to ZVDT z/OS using a remote 3270 terminal emulator
Problem Determination
  • Ensure that you have network connectivity to the Linux® adapter by pinging the Linux adapter IP address from the machine that is running your remote 3270 terminal emulator
  • Ensure that you have a tunnel OSA defined with an internal 10.x.x.x address. Ensure that there is a matching route that sends all 10.x.x.x traffic through the tunnel OSA
  • Ensure that the remote 3270 terminal emulator configuration is attempting to connect to the Linux IP address or host name, and port 3270 (or whatever port is defined on the 3270port statement)
  • Ensure that your firewall configuration allows traffic to the 3270port. See Firewall considerations in “Configuring the base Linux Server” above for how to configure the firewall to allow the appropriate ports.
Symptom Cannot ping to a z/OS defined IP address on the ZVDT instance.
Problem Determination
  • Ensure that you have a tunnel OSA defined with an internal 10.x.x.x address. Ensure that there is a matching route that sends all 10.x.x.x traffic through the tunnel OSA
  • You can only ping to the z/OS IP address when an IP address is assigned that is advertised to the network attached to the Linux ethernet adapter.
    • Defined a 2nd OSA, with an IP address in the same subnet as the IP address of the Linux ethernet adapter
    • Defined a default route through that OSA
    • Updated your TCPIP.DATA files to point to your domain name server and the host name for your z/OS
    • Updated your procedures to point to the new TCPIP.DATA files
    • Updated your IPNODES definitions to include the z/OS host name and IP address

    • Updated your resolver parms to point to the new IPNODES definitions

    • Updated your VTAM definitions to add the tunnel OSA and any other OSAs defined
Symptom Cannot FTP or Telnet to a z/OS defined IP address on the ZVDT instance
Problem Determination
  • Verify that you can ping to the address from the remote location. If you cannot, follow the steps defined here.
  • If you can ping, check your firewall configuration with the command 
    iptables -L -n
    • Ensure that the appropriate ports are allowed; typically ports 21 for FTP and 23 for Telnet