This week one of our AS400 got me all surprised. I do not know what to do, where to look, so I would like to ask here...just in case.
On this AS400, among others there are four host table entries. These entries are set to 2.xxx.xxx.xxx addresses. The DNS has 9.xxx.xxx.xxx addresses. Customer does not want to use those 9* ones,so they decided to bypass it with the local host table.
Host table contains four names with 2.xxx.xxx.xxx addresses.
DNS server table contains the same four names with 9.xxx.xxx.xxx addresses.
Host name search priority *LOCAL.
24 hours after an IPL, one of the four stopped communicating with the AS400 (was unreachable from the AS400)
PING to 2.xxx.xxx.xxx address ok.
PING to 9.xxx.xxx.xxx address timed out (obviously)
PING to the name returned 9.xxx.xxx.xxx address - therefore could not communicate.
Last PTFs installed 2 weeks ago onto other 20 partitions. No reports from the others.
No recent changes to DNS or host table.
Nothing in history log since the IPL. Nothing in QSYSOPR since the IPL. (searched for QTCP, not resolved, communication, TCPIP).
TCPIP started successfully during the IPL. Not restarted since the IPL.
We run on V6R1.
I did not run SST Communications Trace (pitty, I could have)
When I removed the host table entry, waited a few seconds and added it back, the communication was established.
PING to the name returned 2.xxx.xxx.xxx address.
It is working since then.
My questions are:
- what could have caused it?
- is there any kind of fix to this?
- how to prevent it from happening again?
Any reponse and help are highly appreciated.