Just a question of curiosity: If I have AD setup with 3 sites (Both in AD and physical), how does a computer logging on in Site A know to grab the info from the DHCP / DC Server in Site A rather than Site B or C? Is it response time when it sends out a request for an IP?

hi there, i would like to give you a brief note about what happens when a client logs into specific dc .When a logon request is made to a domain, the workstation sends out a request to find a domain controller for the domain. The domain name is actually a NetBIOS name that is a 16-character name with the 16th character used by Microsoft networking services to identify the NetBIOS type.The type used for a domain controller is <1C> and so the NetBIOS name for domain controller of domain "TEST" would be "TEST <1C>" The NetBIOS type has to be the 16th character, hence the name of the domain has to be filled with blanks to make its length up to 15 characters.If the client is WINS enabled then a query for the resolution of "<domain name> <1C>" will be sent to the WINS server as defined in the clients TCP/IP properties. The WINS server will return up to 25 IP addresses that correspond to domain controllers of the requested domain, a \mailslot\net\ntlogon is broadcast to the local subnet and if the workstation receives a response then it will attempt logon with the local domain controller.If WINS is not configured then it is possible to manually configure the LMHOSTS file on the Workstations to specify the Domain Controller. This file is located in the %systemroot%\system32\drivers\etc directory.An example entry in LMHOSTS would be as followsIPaddressclient#PRE #DOM:test #test domain controllerThe above sets up IP address to be host client, which is the domain controller for TEST and instructs the machine that this entry is to be preloaded into the cache.To check the NetBIOS name cache you can use command nbtstat -c, which will show all the entries including their type. If WINS is not configured and there is no entry in LMHOSTS then the Workstation will send out a series of 3 broadcasts. In the situation where no response is received and WINS is configured to use DNS for WINS resolution a request to the DNS server will be sent and finally the HOSTS file checked. If all of this fails then an error "A domain controller for your domain could not be contacted.in the above process, both Netbios and DNS protocols are used. so it depends on DNS ip address you have configured and wins server if configured.sainath Windows Driver Development

Hello Mack879w,First does all your 3 sites have atleast one Domain Controller? For DHCP, if you only have one in your network, you will have to set it up to relay IPs to all sites. But for Domain controllers, it is a little different, First, a client will look a DC in their local site\subnet first and if there is none, they will look for the first available DC basedon the site cost settings. So if there is a DC in site A, then clients in that site will by default automatically use that DC.Hope this helps,Isaac Oben MCITP:EA, MCSE