User Guide for Cisco Prime Network Registrar, 8. Configuring High- Availability DNS Servers . This configuration is called High- Availability (HA) DNS. The Cisco Prime Network Registrar web UI and CLI have features with which you can duplicate the primary setup required for HA DNS for the server pair. The server pair is responsible for detecting communication failures and the like. After the HA DNS is configured, the shadowing and error detection is done automatically.
In a Cisco Prime Network Registrar deployment where Cisco Prime Network Registrar DHCP is updating Cisco Prime Network Registrar DNS, the failure detection and failover also happens automatically. The main server processes all DNS updates from clients and sends all accepted updates to the hot standby backup. The main server will forward RR updates to the backup server and the backup server only accepts updates from the main in normal state. In normal states, updates from DDNS clients are ignored or dropped by a backup server. Both servers can respond to queries and zone transfer requests. The main and backup partners exchange heartbeat messages to detect if the other is not available. When the main returns, the backup sends it the updates, and the main synchronizes with the backup any updates that were not sent and which it had before it went down.
But from release 8. Session Edit Mode is Synchronous by default. This allows updates to all other zones while a given zone is in the process of getting synchronized. When the backup server comes back up, the main sends the recorded updates to the backup.
In this state, the servers do not accept DNS updates or RR edits, and they defer scavenging, if enabled. In this state, DNS Updates and RR edits are not allowed. The main accepts DNS updates and RR edits, sends RR Update messages to the backup, and performs history trimming and scavenging, if enabled. The backup ignores DNS updates, refuses RR edits, but processes RR Update messages from the main server.
The backup also performs history trimming, but defers scavenging, if enabled. In this state, the synchronization takes place. The server continues listening for communication from the partner (they both send heartbeat messages every 1. DNS updates and RR edits and disabling scavenging.
This manual intervention is possible only in Communication- Interrupted state. Either server continues listening for communication from the partner and tries to connect, accepts DNS updates and RR edits, and performs scavenging. Tries to establish a connection with its partner. Transitions to Negotiating state. Transitions to Normal state, after it receives a Negotiating response. Zone synchronization is always managed by the Main HA server. The zones traverse through the following states: .
In this state RR updates for the zone will be accepted on the main server, and forwarded to the backup server. RR updates are not accepted, and notifies are disabled. In this state, the zone on the HA DNS main server accepts all dynamic DNS update requests, allow resource record configuration changes, and re- enables notifies.
- Thanks for choosing OpenDNS! To get started, you’ll need to set up one or more of your devices to use OpenDNS’s DNS nameservers. For instructions on how to do this, choose your device type from one of the categories below.
- In this configuration BIND9 will find the answer to name queries and remember the answer for the next query.
- In a Cisco Prime Network Registrar deployment where Cisco Prime Network Registrar DHCP is updating Cisco Prime Network Registrar DNS.
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Resource record modifications will be forwarded to the backup server. The zone will accept resource record updates on the main server, and changes will be forwarded to the backup. The server will retry synchronizing the zone after ha- dns- zonesync- failed- timeout. A manual sync request or server restart will also restart zone synchronization. From the DHCP side of HA DNS, the DHCP server sends DNS updates to a single DNS server at a time. The DHCP server tries to contact the main DNS server, twice.
It tries the backup partner if both of the attempts are unsuccessful. When the servers come up again, HA communication will be automatically established and the servers will get into Normal state where they carry out zone synchronization and make sure that both have the same RRs, etc. If both servers are unreachable or unresponsive, the DHCP server continually retries each DNS partner every 4 seconds until it gets a response. The following three options are provided: .
In this video you will see how to install Active Directory, DNS Server and DHCP Server installation and configuration in Windows Server 2012.
The sync is run using the HA server algorithms by default. In Expert mode, the following three options are provided: . Status includes count and percentage of synchronized zones, zones pending synchronization, and zones that have failed synchronization. The preset value is 3. The server tries to communicate and then back off at multiples of the ha- dns- comm- timeout interval.
Cisco CallManager DNS Configuration Issues Document ID: 13930 Contents Introduction Prerequisites Requirements Components Used Conventions Configuration Issues with Cisco CallManager 3.0(1) Change the DNS Server and Domain.
The preset value is enabled. Step 2 From the DNS menu, choose HA Pairs to open the List/Add HA DNS Server Pairs page. Step 3 Click Add HA DNS Server Pair to open the Add HA DNS Server Pair page. Step 4 Enter the name of the server pair in the Name field. This can be any identifying text string.
Step 5 Click the cluster name of the main DNS server in the Main Server drop- down list. Note If you change the IP address of your local host machine, you must modify the localhost cluster (on the Edit Cluster page) to change the address in the IP Address field. Do not set the value to 1. Step 6 Click the cluster name of the backup DNS server in the Backup Server drop- down list. This cannot be the same as the main server cluster.
Set the ha- dns- main- server and ha- dns- backup- server attributes only if the server is configured with different interfaces for configuration management and update requests. Step 8 Once the server pair appears on the List/Add HA DNS Server Pairs page, synchronize the servers: a. Click the Report icon in the Synchronize column. On the Report Sync HA DNS Pair page, choose the direction of synchronization (Main to Backup or Backup to Main). Choose the operation type (Update, Complete, or Exact). See the table on the page for details on the operations for each operation type. Click Report to display the prospective synchronization changes on the View HA DNS Sync Report page.
Click Run to complete the synchronization and view the actual changes. The configuration gets pushed to the remote cluster.
Click Return to return to the List HA DNS Server Pairs page. Note To view the HA DNS server status, click the () icon next to the HA DNS pair name. This opens the View HA DNS Server Status page. Step 9 Reload both DNS servers to begin HA communication. Then synchronize the servers using ha- dns- pairnamesync, specifying the synchronization operation (update, complete, or exact) and direction (main- to- backup or backup- to- main).
Be sure to reload both DNS servers. For example: nrcmd> ha- dns- pair examplehadnspair create localhost test- clusternrcmd> ha- dns- pair examplehadnspair sync exact main- to- backupnrcmd> dns reload See the ha- dns- pair command in the CLIGuide. The CLI provides an additional command for the DNS server to set the HA DNS partner down, if necessary, which is possible only while in Communication- Interrupted state: nrcmd> dns set. Partner. Down The partner down is useful because it limits the bookkeeping data a server maintains, thus optimizing its performance. When both servers start communicating again, the sync sends all the zone RRs rather than trying to determine individual changes. Note The HA communications with versions earlier to 8.
So, you have to upgrade both the main and the backup servers in the same maintenance window. Step 2 Click the command () icon for the zone which you want to synchronize. This opens the Zone Commands for Zone page. Step 3 Click the () icon next to Synchronize HA Zone to synchronize the HA DNS zone. Note In the Expert mode, you have the option to choose the type of synchronization.
The Use Server Algorithms option is checked by default. If you click the () icon next to the Synchronize HA Zone without choosing another option, server algorithms will be used to synchronize the zone. You can override this by checking either Push Full Zone From Main to Backup check box or Pull Full Zone From Backup to Main check box. When you enable the HA DNS with large DNS configuration, you will notice that the process takes long time to complete. This section provides a workaround, which you can use until the defect is addressed. During the installation process, the installer will verify whether any previous configuration is up to date with the Cisco Prime Network Registrar data schema for the version being installed.
Even if the versions are identical, the time required to perform this verification can be avoided by pre- installing Cisco Prime Network Registrar on the HA DNS backup system. If the servers are found on the same system, the migration from HA DNS main server to backup server may cause DHCP or TFTP conflicts, and DHCP clients may be destabilized. Note The default setting of start- on- reboot for the TFTP server is disabled. Step 3 Once the Cisco Prime Network Registrar is stopped by using Windows Process Manager (Windows) or ps command line utility (Linux/Solaris), navigate to the parent directory of the Cisco Prime Network Registrar data directory, Install. Dir\Network Registrar\Local\ (Windows) or /var/nwreg.
Linux/Solaris). Step 4 Using tar or an equivalent compression utility, bundle up the contents of the data subdirectory. Install. Dir is the directory where you have installed your Cisco Prime Network Registrar: tar - cvf cnrdatadir.
Tip Replace all the . HA DNS main server.
The HA backup server does not need these backup directories and replacing them reduces the overall archive size. Be sure that you do not replace any other database files other than . HA DNS backup cluster may not function properly. Step 2 Restore the DHCP and TFTP server start- on- reboot attribute values to their pre- migration values: nrcmd> server dhcp enable start- on- reboot. Copy Cisco Prime Network Registrar Database Files to HA DNS Backup Server Step 1 Use FTP or an equivalent network file copy mechanism to transfer the Cisco Prime Network Registrar database archive that was generated in the previous step to the parent directory of the Cisco Prime Network Registrar data directory (typically C: \Network. Registrar\Local\ on Windows, and /var/nwreg.
Dev Environment: Install and configure BIND DNS Server in Windows 7. Power up your Web Developer environment installing Bind 9 DNS Server. Specially it will delight you if you are using Virtual. Box or Vagrant to run your Back- end stack, but your browser still is in the Host OS, in this case Windows (More about this in the next blog post)These are the main benefits you will get: You want to have a domain *.
IP of your Virtual Machine. It allows you to run complex forwarding rules, including port forwarding. Forget the limitations of the Windows hosts file. Bind acts also as local DNS Cache: maximum performance when browsing. That's the reason I created this tutorial.
I got some tips from DNS and BIND book, that you might want to check also. Let's go: 1. Download BIND (latest release now is 9. P3) 2. Let's start with the Installation: In the installer window, leave the default name . In System Properties => Environment Variables, find the variable PATH and append the string ; %SYSTEMROOT%\Sys.
WOW6. 4\dns\bin; (in case of Windows 6. SYSTEMROOT%\system. Windows 3. 2 bits. Search for the DOS prompt cmd. Now browse to: C: \Windows\Sys. WOW6. 4\dns\etcor in Windows 3.
C: \Windows\system. By default the dns\etc folder is empty. Execute the command: rndc- confgen - a. This will create a file rndc.
In some tutorials you will see a extra step to create a rndc. BIND Configuration files: Let's configure Bind. It's better to run notepad commands directly from the already opened . Later when you get the DNS server working, change it to severity: warning. All the options for the logging are explained here. There is no controls statement, so the default configuration will be Bind running on 1. If you are curious, the full list of statements that can be used (with default values in bold).
Use that IP in your DNS configuration of your Internet Connection, and you will start using Bind to resolve DNS lookups. If for some reason it's not working and you are trying different BIND configurations, check the named. Each time you change the configuration you will need to follow these 2 steps, in this order: ipconfig /flushdns. Or you can reload the BIND Service from the GUI too. See the screenshot: That's all.
You should be able to surf the web normally and you could disable the Windows built- in DNS Cache Client (in the Services). The purpose of this first part is to have a minimalistic configuration to get BIND running with logging so it's easier to debug if you run into problems. But with this configuration, you are letting Bind to resolve the DNS using its built- in list of root name servers, a quite slow process.
DNS Lookups can take as much as 3 seconds. You can tell to Bind to forward the requests to a faster DNS services, like Google's 8. Change the options of your named. Now the DNS lookups are taking in my case about 2. If you want to optimize your DNS configuration, run some Benchmark with any of these tools: GRC DNS Benchmarking or Name. Bench. Here are some screenshots from Helsinki, a Welho Cable connection: Let's explore more advanced configuration and options in the next blog post. I will post it in Twitter or by RSS.
Extra: Tips for debugging DNS issues and more. Hint: Almost every DNS problem I had configuring BIND and testing were because a DNS Cache in my way: Query logs.
This useful command will make that all DNS lookups are logged in the named. If you reload the service, it will stop. About the internal Windows DNS Cache.
You can locate this Service by the name . Related commands: To inspect the Windows DNS Cache: ipconfig /displaydns. To clear the Windows DNS Cache: ipconfig /flushdns. Tip: Create a shortcut in the Desktop with the value . I don't use them, but it's nice to know that exists. Dig and nslookup own DNS Cache. The dig and nslookup commands are quite independent from Windows.
These commands use their own DNS Cache, and they bypass the Windows DNS Cache. For example. If Windows DNS Cache has already cached drupal. DNS Cache Service, then dig drupal.
In the other hand, ping drupal. Windows DNS Cache before hitting the DNS Server. About your browser DNS Cache.
When debugging issues about DNS, remember that your browser also stores internally the DNS lookups. Normally a CTRL + F5 should be enough to clear. This (one year old) chart shows you specific times: Source: http: //dyn. About Fiddler. If you use fantastic tool Fiddler, be aware that has its own DNS Cache that will interfere with your tests.
Look my Stackoverflow question, where Eric answered. After following that advice, it's the most reliable tool I've found to inspect DNS lookups. About Firebug. I wouldn't rely on the DNS Lookup Time of the Network tab. Always is 0 ms, even when it takes several seconds for the DNS request.
About Navigation Timing APITodo: Test accuracy of Navigation Timing API. I will update soon. Extra: Resources. The single best guide for BIND I found is the book Pro DNS and BIND, available for free, who has also installation guides for every OS, including Windows 7.
And more recent book about DNS is DNS and BIND.