[Xymon] What does the 'dns' test do?
mailinglists at websitemanagers.com.au
Wed Mar 13 00:18:51 CET 2019
On 13/3/19 12:19 am, John Horne wrote:
> On Sun, 2019-03-10 at 21:17 +0000, John Horne wrote:
>> Using the 4.3.28 Terabithia RPMs, can someone tell me what the 'dns' test
>> actually does?
>> We actually negate the test ('!dns'), and run a client-side dns test ('dnsr')
>> to check that resolution is working. As far as I remember the standard 'dns'
>> test checks that the client DNS service can resolve something. This will
>> always fail in our case as the client DNS service is always restricted to
>> just the local host. (No querying allowed from an external server.)
>> I'm trying to work out why most of our servers are taking less than a second
>> - giving a 'Server unavailable' reply, but others are taking around 20
>> seconds for a 'Timeout' reply. I know why the timeout is 20 seconds, I'm just
>> wondering why it's not giving a 'Server unavailable' reply.
> Thanks for the replies about this.
> It seems the network infrastructure in which our monitoring server sits is
> blocking ICMP from some networks. Clients in those networks are correctly
> sending back an ICMP reject via its local firewall, but these are blocked. So
> the Xymon server times out the connection instead. I've asked if ICMP rejects
> can be allowed through.
Maybe also refer them to this: http://shouldiblockicmp.com/
ie, don't block all ICMP.... some is required so that the Internet thing
Adam Goryachev Website Managers www.websitemanagers.com.au
The information in this e-mail is confidential and may be legally privileged.
It is intended solely for the addressee. Access to this e-mail by anyone else
is unauthorised. If you are not the intended recipient, any disclosure,
copying, distribution or any action taken or omitted to be taken in reliance
on it, is prohibited and may be unlawful. If you have received this message
in error, please notify us immediately. Please also destroy and delete the
message from your computer. Viruses - Any loss/damage incurred by receiving
this email is not the sender's responsibility.
More information about the Xymon