Background: I have a client who has a DC that was converted from 2008 to 2012R2. the 2008 server is still active on the network, but was demoted. the 2012 server is the DC and runs the DNS. The 2008 server that was the DC still runs the DHCP. There were issues during the conversion- but the conversion happened about 5 months ago. to get the conversion to work the regedit to set burflags d4/d2 had to be done. once that was done the conversion did complete successfully. no issues up until a few weeks ago.
Issues: The 2012 server could not get to the internet about 90% of the time. the other 10% of the time it will work fine, until the browser is closed and once re-opened it doesnt work. Page cant be displayed message. Also the 2012 server can not access file shares on the 2008 server unless you browse to it by ip address.
When we add the A record for the 2008 server to DNS in appears and successfully adds but in just a couple minutes it goes away? like it is auto deleted?
We decided to change Nic's on the 2012 server and when we disabled the nic, we looked at DNS and the 2008 server had showed up, but as the ip address of the 2012 server? 192.x.x.5, the 2008 server used to be the .5 address when it was the DC, but it was changed when the new 2012DC was installed. we changed it to .7 and made the 2012 DC .5 address?
Ran dcdiag on the 2012DC and there are all passes with the exception of the System log and it has some odd errors. referencing Kerberos and Ip addresses and the 2008 server name. I'm not sure why that would be showing in the syslog on the 2012 server?
I'm terribly stumped at the issues...It doesnt seem to be affecting workstations at this point but something is definitely amiss. I doubt there is a silver bullet for this situation but welcome feedback, questions, links and assistance! Many Thanks
Update: We changed to a different NIC on the 2012 server and assigned the same static IP address and now internet has worked longer than it has in about 3 weeks. still can not access file shares on the 2008 server from the 2012 server. and the A record on the 2008 server still is not retained.