Only the machine with the software.
From: [email protected] [mailto:[email protected]] On
Behalf Of Melvin Backus
Sent: Thursday, April 24, 2014 6:16 AM
To: [email protected]
Subject: [NTSysADM] RE: DNS server settings getting changed
No, it's changing back to our domain DNS. Just curious though, did that only
affect the machine with the software or was it able to touch other machines
across the network?
--
There are 10 kinds of people in the world...
those who understand binary and those who don't.
From: [email protected]<mailto:[email protected]>
[mailto:[email protected]] On Behalf Of Jimmy Tran
Sent: Thursday, April 24, 2014 9:12 AM
To: [email protected]<mailto:[email protected]>
Subject: [NTSysADM] RE: DNS server settings getting changed
Had this problem happen to two different clients. The machines someone got
some software called DNSchanger installed. It would change DNS to 8.8.8.8 and
8.8.4.4.
Are those the IP's its changing to?
From: [email protected]<mailto:[email protected]>
[mailto:[email protected]] On Behalf Of Melvin Backus
Sent: Thursday, April 24, 2014 5:27 AM
To: [email protected]<mailto:[email protected]>
Subject: [NTSysADM] DNS server settings getting changed
OK, this has been driving us nuts for a couple of days now.
One of our remote sites is seeing seemingly random PCs change their DNS server
settings. They're all configured to get them from the DHCP server, and it has
the correct DNS servers. All the PCs do in fact get the correct settings when
they get or renew an IP. That all seems to be working as we expect. But
periodically we'll see a machine change the DNS servers to something else.
This causes applications to start failing because the hosts they need no longer
resolve. As soon as the PC renews it's IP, whether automatically or manually,
everything goes back to normal and stuff works again.
We have a short term fix (force the DNS server settings manually instead of
DHCP) but that doesn't explain what's going on, and since we're using this same
setup in 20 offices it also begs the question of why just this office.
Background:
Multiple small offices with either /28 or /27 networks. They are publicly
routable IPs due to requirements for a partner VPN. The DHCP server is on the
Juniper SSG FW. It servers two pools, one for PCs, another for phones. The PC
subnet is publicly routable, the phone subnet is a non-routable 10.x subnet
with matching ranges. (12.x.x.x/27 and 10.x.x.x/27). All DNS points to the
home office. Until recently these pointed strictly to our domain DNS servers.
As part of the VPN requirement we have set up a second set of DNS servers which
are used to resolve hosts in the partner's domains. This is done with
conditional forwarders. Partner DNS traffic gets resolved by their servers,
everything else goes to our domain DNS or the Internet as required.
This all works fine except in a single office. Even in that office it worked
fine for weeks and has suddenly started this "revert" behavior. When the PCs
change, they go back to pointing to our domain DNS which can't resolve the
partner hosts.
My question becomes (sorry it took so long) how do we track what is actually
changing the DNS settings? I can tell when it happens fairly easily, but
nothing in the event logs, etc., seems to indicate what triggered it, or what
process is doing it. It doesn't happen as part of a DHCP operation as best we
can tell.
--------------------
Melvin Backus | Sr. Systems Analyst | Byers Engineering Company | 404.497.1565
Service Desk | 404-497-1599 | http://servicedesk.byers.com
--
There are 10 kinds of people in the world...
those who understand binary and those who don't.
