here is a section of my netlogon.log i have been reading about how netlogon builds its dns request from the information it collects. but not sure where this information is stored i have setup wireshark as well  i can see that the dns request sent is invalid as well _ldap._tcp.dc1.mydomain.com  should be _ldap._tcp.mydomain.com which is in my dns?

is this normal?

I have checked my dns and confirmed this is not a dns issue

it is what the client is requesting that seems to be  wrong

03/25 19:51:09 [MISC] DsrEnumerateDomainTrusts: returns: 0
03/25 19:51:09 [MISC] DsGetDcName function called: Dom:Mydomain Acct:(null) Flags: DS RET_DNS 
03/25 19:51:09 [MISC] NetpDcInitializeContext: DSGETDC_VALID_FLAGS is c01ffff1
03/25 19:51:09 [MISC] NetpDcGetName: mydomain.com. using cached information
03/25 19:51:09 [MISC] DsGetDcName function returns 0: Dom:Mydomain Acct:(null) Flags: DS RET_DNS 
03/25 19:51:09 [MISC] DsGetDcName function called: Dom:mydomain.com Acct:(null) Flags: DS BACKGROUND RET_DNS 
03/25 19:51:09 [MISC] NetpDcInitializeContext: DSGETDC_VALID_FLAGS is c01ffff1
03/25 19:51:09 [MISC] NetpDcGetName: mydomain.com using cached information
03/25 19:51:09 [MISC] DsGetDcName function returns 0: Dom:mydomain.com Acct:(null) Flags: DS BACKGROUND RET_DNS 
03/25 19:51:10 [MISC] DsGetDcName function called: Dom:DC1.mydomain.com Acct:(null) Flags: LDAPONLY RET_DNS 
03/25 19:51:10 [MISC] NetpDcInitializeContext: DSGETDC_VALID_FLAGS is c01ffff1
03/25 19:51:10 [CRITICAL] NetpDcGetNameIp: DC1.mydomain.com: No data returned from DnsQuery.
03/25 19:51:10 [MISC] NetpDcGetName: NetpDcGetNameIp returned 1355
03/25 19:51:10 [CRITICAL] NetpDcGetName: DC1.mydomain.com: IP and Netbios are both done.
03/25 19:51:10 [MISC] DsGetDcName function returns 1355: Dom:DC1.mydomain.com Acct:(null) Flags: LDAPONLY RET_DNS 
03/25 19:51:10 [MISC] DsGetDcName function called: Dom:DC1.mydomain.com Acct:(null) Flags: LDAPONLY RET_DNS 
03/25 19:51:10 [MISC] NetpDcInitializeContext: DSGETDC_VALID_FLAGS is c01ffff1
03/25 19:51:10 [MISC] NetpDcGetName: DC1.mydomain.com similar query failed recently 16

To be honest I'm unsure of what specifically in the dcLocator you are having problems with.

_ldap._tcp.dc1.mydomain.com
Is probably a call to your PDCe

From a command prompt:
netdom query FSMO

Is DC1 your PDCe?

Ace has a great blog on the dcLocator Process
http://msmvps.com/blogs/acefekay/archive/2010/01/03/the-dc-locator-process-the-logon-process-controlling-which-dc-responds-in-an-ad-site-and-srv-records.aspx

can you enable dns client logging 

do a gpupdate and see if your client machine does a srv query for _ldap._tcp.domaincontrollername.domainname.com

and see if you get a reply from your dns 

i dont think that this is causing us any issue but it looks like a bug in the netlogon process

I see the same behavior. Have yet to come up with an explanation.

I have opened this serverfault.com question on the same topic:

http://serverfault.com/questions/669884/windows-hosts-dns-query-for-ldap-tcp-domaincontroller-is-this-normal

I also see queries like these:

_ldap._tcp.oursite._sites.deecee.internal.foo.bar  
_ldap._tcp.deecee.internal.foo.bar  
_ldap._tcp.oursite._sites.dctoo.internal.foo.bar  
_ldap._tcp.dctoo.internal.foo.bar  
_ldap._tcp.deecee                           <- only from our sharepoint hosts  
_ldap._tcp.oursite._sites.decee  
_ldap._tcp.oursite._sites.dctoo  
_ldap._tcp.dctoo                            <- only from our sharepoint hosts