nslookup and dns failure

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NotAllThere replied

8 April 2023, 10:01
I'll try various of these things when I'm back at work on Tuesday.
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DealorNoDeal replied

8 April 2023, 09:31
Originally posted by NotAllThere View Post

It sometimes works, sometimes doesn't.

Does ping -a ip_address reveal anything?
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NotAllThere replied

8 April 2023, 08:15
Originally posted by PerfectStorm View Post

Some domains have ping blocked dont they - could be that

It sometimes works, sometimes doesn't.
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PerfectStorm replied

7 April 2023, 18:56
Some domains have ping blocked dont they - could be that
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NotAllThere replied

6 April 2023, 15:19
Sorry. Bunch of typos in the original post. Fixed now.

I tried my workaround again and it seems it was coincidence. Putting the ip address directly works.
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Lance replied

6 April 2023, 09:18
Originally posted by NotAllThere View Post

Can anyone explain this? Windows 11.

I ping something like myserver.nat.com and get: Ping request could not find host myserver.nat.com. Please check the name and try again.
I then nslookup myserver.nat.com and get something like
Server: mydnsserver.nat.com
Address: 10.1.1.1

Name: myserver.nat.com
Address: 10.1.1.2

And now the ping works.

If I pinged something of mine and got a response based on a different name, it suggests it found a CNAME record rather than an A record. Nslookup should show CNAME lookups as aliases.

Like this lookup to an autodiscover CNAME

C:> nslookup autodiscover.domain.com

Server: custcache01.dns.zen.net.uk
Address: 212.23.3.100

Non-authoritative answer:
Name: autod.ms-acdc-autod.office.com
Addresses: 2603:1026:c06:141e::8
2603:1026:c06:23::8
2603:1026:c06:1f::8
2603:1026:c06:180d::8
52.97.211.168
52.97.129.72
52.97.129.248
52.97.179.248
Aliases: autodiscover.domain.com
autodiscover.outlook.com
autod.ha-autod.office.com

and the corresponding ping would be

c:\> ping autodiscover.domain.com

Pinging autod.ms-acdc-autod.office.com [52.97.211.72] with 32 bytes of data:
Reply from 52.97.211.72: bytes=32 time=14ms TTL=243
Reply from 52.97.211.72: bytes=32 time=15ms TTL=243
Reply from 52.97.211.72: bytes=32 time=14ms TTL=243
Reply from 52.97.211.72: bytes=32 time=20ms TTL=243
Leave a comment:
jamesbrown replied

5 April 2023, 08:44
Windows is probably caching the result of the DNS nslookup so that ping doesn’t then attempt it until it’s deleted from the cache. The ping command ordinarily needs to do the DNS lookup of your hostname and then send/receive packets. If the lookup part fails via ping, I think that would explain it. As to why it fails intermittently, I have no idea. Does it ever fail if you ping the FQDN, for example?
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DealorNoDeal replied

5 April 2023, 08:08
Weird.

After you've done nsloopup myserver.nat.com, how long does ping myserver.nat.com keep working? Just for that CMD session, or until you reboot?

When you get the failure, the following might reveal something:

ping -a 10.1.1.2
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NotAllThere started a topic nslookup and dns failure

5 April 2023, 07:47
nslookup and dns failure

Can anyone explain this? Windows 11.

I ping something like myserver.nat.com and get: Ping request could not find host myserver.nat.com. Please check the name and try again.
I then nslookup myserver.nat.com and get something like
Server: mydnsserver.nat.com
Address: 10.1.1.1

Name: myserver.nat.com
Address: 10.1.1.2

And now the ping works.
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