I was trying to go from z/OS running on zD&T system on a Linux server to the external internet. It was very frustrating in that a ping to a site would not work, I made an adjustment, ping still didn’t work, I made another adjustment, and then it worked. I then undid the adjustments and it worked! I optimised this by doing 3 pings – the first two failed, then it worked.
If I re-ipled – it worked. If I shutdown, and restarted the Linux server – it failed the same way.

My configuration

I had the default for IPV4 going to address 192.168.1.22. This was the value of the connection if I used FIND_IO or ip addr.

What I saw was

1. Source 192.168.1.25 -> 151…. this did not work ( no response )
2. Source 192.168.1.25 -> 151…. this did not work ( no response)
3. Source 192.168.1.22 Redirect ICMP request gateway 192.168.1.254.
   • src 192.168.1.25 -> 151… worked

What was happening was my request with IP address 192.168.1.25 was being routed (because of my routing definitions) to 192.168.1.22. I don’t know if the request ever got out of my Wireless router, or the site I was pinging was unable to send a response back. After the second of these incidents the “router” with address 192.168.1.22 send a redirect message to my original node saying instead of sending me the traffic – send it directly to address 192.168.1.254 which is my wireless router’s address.

I changed the routing to be 192.168.1.254 – and next time I restarted my server, and reipled z/OS, I could ping and it worked every time.

Lesson learned

I learned that it is important to get the right definitions.

I also learned that making a change, and when you undo the change, you do not always get back to the original state.