Configuring Secondary DNS Servers
This section covers the configuration steps for a secondary DNS server. Secondary servers have a local read-only copy of a zone file that is pulled from a master name server. Secondary servers are authoritative for their zones, but cannot make changes to the zone. This section also covers the steps necessary to configure a master name server to accept zone transfer requests from a secondary and to notify the secondary when zone updates have occurred.
The initial service installation for a secondary DNS server is the same as for a primary server. Only the zone configuration steps differ. Load the service drivers using the steps in "Installing and Configuring DNS Servers," earlier in this chapter, and then return here.
Enabling Zone Transfers and Update Notifications
A secondary server cannot pull a zone until zone transfers and notifications are enabled at the master name server. To enable these options, follow Procedure 5.12.
Procedure 5.12 Enabling Zone Transfers and Notifications
Open the DNS console.
Right-click the zone icon and select PROPERTIES from flyout menu. The Properties window opens.
Select the Zone Transfers tab. Select the Allow Zone Transfers option. There are three notification options:
To Any Server.
This is self-explanatory and not recommended. This permits any server or user to pull a zone from your name server. A comprehensive list of host names and IP addresses is not something that you want in unauthorized hands.
Only to Servers Listed in the Name Servers Tab.
This option limits zone transfers to servers with NS records in the zone file. This is the preferred option because it does not involve keeping two lists of servers (actually three lists, because you must also maintain a notification list). If you delegate to untrusted domains, however, you may not want to select this option because it permits administrators of the delegated name server to pull a zone.
Only to the Following Servers.
This option gives you the most control over zone transfers by identifying each authorized secondary individually. This does not prevent an intruder from spoofing the IP address of a secondary so that it can initiate a zone transfer, but it's better than leaving the door wide open.
Click Notify. The Notify window opens. Update notification is enabled by default in Windows Server 2003. This ensures that the zone files on the secondary name servers are kept current. You have the option in this window of automatically notifying servers in the NS list or specifying servers. If you chose the Only to the Following Servers option in the previous window, you must also individually select secondary servers for notification.
Click OK to save the notification settings and return to the Properties window.
Click OK to save the zone transfer settings and return to the DNS console.
Close the DNS console.
Test both the zone transfer setting and update notification by adding a test record at the primary. After refreshing the DNS console at the secondary, the record appears on the list. If this does not occur, check the IP addresses and notification settings.
Configuring a Secondary DNS Server
An authoritative secondary name server maintains a local copy of the zone. It uses root hints or a forwarder to handle queries that are outside of the zone.
If you have configured a master name server to do zone transfers only with selected secondaries, you must first add the IP address for this server to the list. You should also include the new secondary on the list of secondary servers to notify for updates. To configure the secondary server, look at Procedure 5.13.
Procedure 5.13 Configuring a Secondary Server
Open the DNS console.
Right-click the Forward Lookup Zone icon and select NEW ZONE from the flyout menu. The New Zone Wizard starts.
Click Next. The Zone Type window opens. Select Secondary Zone.
Click Next. The Zone Name window opens. Enter the FQDN name of the zone you are going to transfer to this server. For example, enter company.com.
Click Next. The Master DNS Servers window opens.
Enter the IP address of the master name server that you designated for use by this secondary and click Add to add it to the list. You can pull zones from several masters.
Click Next. The wizard displays a completion window.
Click Finish to close the wizard and return to the DNS console. The zone is transferred automatically.
Verify that you got the zone file records by refreshing the tree. If you get a big red X with a Zone Not Loaded error, press F5 to refresh again. If the red X persists, you possibly forgot to enable zone transfers at the master server and add the secondary to the zone transfer list.
After the secondary server is operational, configure clients to use it and verify by pinging hosts inside and outside the zone. If pings outside the zone do not work, check your root hints at the primary and secondary.