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stop using dns and /etc/hosts

4 messages in this thread

list Ian Diddams · Wed, 4 Mar 2015 12:32:21 +0000 (UTC) · 
I have a hosts.cfg entry

1.2.3.4 server1
where 1.2.3.4 is server1's INTERNAL IP address
but its conn check is red because xymon is actually trying to ping its external, NATTed, address 5.6.7.8 which it cannot reach.
Its because DNS is resolving the IP 5.6.7.8
I can use a local hosts file entry to override that again, but I'd rather have some way fo telling xymon to only use entries in hosts.cfg and ignore native resolution.
How might i achieve that?
cheers
Ian
list Asif Iqbal · Wed, 4 Mar 2015 07:41:32 -0500 · 
Use testip. man hosts.cfg
▸ quoted from Ian Diddams
On Mar 4, 2015 7:32 AM, "Ian Diddams" <user-7fbf34ed5219@xymon.invalid> wrote:

I have a hosts.cfg entry

1.2.3.4 server1

where 1.2.3.4 is server1's INTERNAL IP address

but its conn check is red because xymon is actually trying to ping its
external, NATTed, address 5.6.7.8 which it cannot reach.

Its because DNS is resolving the IP 5.6.7.8

I can use a local hosts file entry to override that again, but I'd rather
have some way fo telling xymon to only use entries in hosts.cfg and ignore
native resolution.

How might i achieve that?

cheers

Ian
list John Thurston · Wed, 04 Mar 2015 08:35:26 -0900 ·
▸ quoted from Asif Iqbal
On 3/4/2015 3:41 AM, Asif Iqbal wrote:
Use testip. man hosts.cfg

On Mar 4, 2015 7:32 AM, "Ian Diddams" <user-7fbf34ed5219@xymon.invalid
<mailto:user-7fbf34ed5219@xymon.invalid>> wrote:

    I have a hosts.cfg entry

    1.2.3.4 server1

    where 1.2.3.4 is server1's INTERNAL IP address

    but its conn check is red because xymon is actually trying to ping
    its external, NATTed, address 5.6.7.8 which it cannot reach.

    Its because DNS is resolving the IP 5.6.7.8

    I can use a local hosts file entry to override that again, but I'd
    rather have some way fo telling xymon to only use entries in
    hosts.cfg and ignore native resolution.
To have Xymon test against the IP address you have specified (rather than relying on DNS or hosts files), use the syntax:

1.2.3.4  server1.foo.com   # testip

fwiw, in my installation, almost all of my lines are of the form:
0.0.0.0  server2.foo.com   # ftp ssh
the only time I provide an IP address with the host is when the line also contains the 'testip' tag. This makes editing my file less error prone and makes it very obvious which hosts respond to name resolution in unexpected ways.

Another way to address this is to have a DNS entry for your internal address and a different entry for it's external (NAT'd) address.
In DNS, it might look like:
server1.foo.com           A  5.6.7.8
server1.internal.foo.com  A  1.2.3.4

In Xymon, hosts.cfg might contain:
0.0.0.0	 server1.internal.foo.com  # name:server1.foo.com

Xymon will perform network tests against a name it can resolve and an address it can reach (server1.internal.foo.com). It will display those results on its web page in a row named server1.foo.com

If you have a client installed on the host also reporting in, it should identify itself as server1.internal.foo.com. If that isn't possible, you can append the tag "client:server1.foo.com" to the end of the line in hosts.cfg. This will permit the xymon server to match client reports from server1.foo.com with the line in the hosts.cfg named server1.internal.foo.com
-- 
    Do things because you should, not just because you can.

John Thurston    XXX-XXX-XXXX
user-ce4d79d99bab@xymon.invalid
Enterprise Technology Services
Department of Administration
State of Alaska
list Jeremy Laidman · Thu, 5 Mar 2015 10:07:49 +1100 ·
▸ quoted from Ian Diddams
On 04/03/2015 11:32 PM, "Ian Diddams" <user-7fbf34ed5219@xymon.invalid> wrote:

I can use a local hosts file entry to override that again, but I'd rather
have some way fo telling xymon to only use entries in hosts.cfg and ignore
native resolution.

How might i achieve that?
You can globally disable all DNS lookups for network tests by adding
"--dns=ip" to the xymonnet command in tasks.cfg.

J