We had a somewhat similar problem a few years ago. In our csse it turned
out to be a firewall issue. An internal name server or resolver was
trying to resolve a host name using an outside name server. The internal
system was sending out EDNS queries, but our Cisco firewall/VPN
appliance had an older version of firmware which couldn't support that
format.
Standard DNS queries must fit into a 512-byte UDP packet. EDNS queries
can be encapsulated in much larger packets. Because of the limitation in
our Cisco's firmware, those EDNS queries were silently being dropped.
The internal system never received a reply and started issuing those
timeout messages.
On 5/8/14, 6:14 AM, גדי בן אבי wrote:
Hi,
Once in a while we receive this series of messages:
14128 13:58:52.67 STC17917 00000090 *EZZ9308E UNRESPONSIVE NAME SERVER DETECTED
AT IP ADDRESS x.x.x.x
14128 13:58:52.67 STC17917 00000090 EZZ9310I NAME SERVER x.x.x.x 409
409 00000090 TOTAL NUMBER OF QUERIES SENT 2
409 00000090 TOTAL NUMBER OF FAILURES 1
409 00000090 PERCENTAGE 50%
14128 14:03:52.68 STC17917 00000090 EZZ9309I NAME SERVER IS NOW RESPONSIVE AT
IP ADDRESS x.x.x.x
14128 14:03:52.68 STC17917 00000090 EZZ9310I NAME SERVER x.x.x.x 257
257 00000090 TOTAL NUMBER OF QUERIES SENT 2
257 00000090 TOTAL NUMBER OF FAILURES 0
257 00000090 PERCENTAGE 0%
The messages are issued by the resolver address space.
Is there a way to find out what is causing these messages?
It looks like some kind of DNS query.
Can I find out what the query was?
We are using z/OS 1.13
Thanks
Gadi
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