Enumeration and Query, Name Resolution and DHCP

During enumeration, UpdateEXPERT discovers machines and uses Windows name resolution services to populate the Master-Agent database with Hostname, FQDN (fully qualified domain name for Active Directory), and resolved IP address information.

Windows uses the following set of mechanisms to resolve the Hostname or FQDN to the target machine's IP address:

The actual lookup order above is dependent on the name used (TCP/IP or NetBIOS) and is affected by the OS network services configured on the Master-Agent . Please refer to the Microsoft web site for more detailed documentation. For example, see:

http://www.microsoft.com/technet/itsolutions/network/evaluate/technol/tcpipfund/tcpipfund_ch07.mspx

DHCP Targets

In DHCP environments where IP address assignments can change due to IP "expirations,"  patch deployments can fail due to stale IP information. In environments with a short "expiration" period for DHCP allocated addresses, failed deployments may occur more frequently due to a faster rate of IP address changes.

This is resolved or minimized by using Enumeration or Query to refresh the network view prior to patch deployment. Enumeration and/or Query prior to patch deployment is already a recommended best practice for a number of reasons un-related to DHCP. For example, Enumeration finds new hosts, and Query refreshes patch inventory information based on the current patch database and state of the target. Using background Enumerate/Query may be helpful, please see:

When does Enumeration Occur?

In summary, UpdateEXPERT will make connection attempts by addressing target machines in the following sequence:

  1. Hostname (Windows Machine Name)

  2. IP Address

    1. Resolved via Windows (see list above)

    2. Manually entered as in Add Machine

    3. Acquired with IP Scan

  3. FQDN (fully qualified domain name in Active Directory)

Note: UpdateEXPERT will remember the last successful connection for each target and use it as the preferred first method for re-connecting. For example, if the last successful connection used the target machine's IP address instead of Hostname, UpdateEXPERT's re-connect attempt will use the IP address first.