Primary DNS Server Requirement for premise-based servers

Explanation

Note: Windows Servers, if serving DHCP/DNS (e.g. active directory, domain controller), should remain the primary DNS, with some configuration additions.  See the Windows Domain Controller section, below.

When setting up your

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system you may wonder “Why Do I need to use

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as my Primary DNS Server for my IP phones?”. This document describes each of them in technical detail, as well as alternatives if your network is unable to specify the

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server as a Primary DNS Server.

The DNS service in the

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system is a very high performance DNS server that’s designed to gracefully handle all of the DNS requirements for all of your IP phones, as well as any network of up to 250 computers. It’s using the same proven BIND DNS software used by all of the root DNS servers on the internet. It’s fast, stable, and secure.

1. Uninterrupted service during an internet outage

   Most small businesses use the DNS services provided to them by their internet service provider. This means that in order for your IP Phones and computers to translate host names to IP addresses they must first query a server on the remote end of your internet connection. If the internet connection is down, or if your ISP’s DNS servers become unresponsive, your IP phones will no longer be able to access your

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   system over your local LAN. By using the

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   server as a primary DNS server for your network, you eliminate this remote dependency, and allow your

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   system to operate properly even during an internet access outage.

    

2. Uses a local database resource rather than a remote one.

   The

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   server maintains a local database resource (called a zonefile) containing the IP address of your

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   server. This allows the

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   system to respond quickly to responses from any of your IP phones without requiring a recursive DNS lookup to any external source. A customer provided DNS server may not have this same performance advantage unless it’s specifically configured that way.

    

3. Prevents de-registered IP Phones.

   DNS Responses (especially from Windows-based DNS servers) can be slow. If/when they are slow, your IP phones will not get a timely response for re-registration, and the registration timeout will expire, causing the phone to be unavailable to the

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   system until the next registration period (typically 10 minutes). Some phones, such as the Swissvoice, need to be manually restarted in order to re-register with the

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   system after a registration timeout problem. When you use the DNS service in your

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   server, these problems never occur, so you don’t need to worry about intermittent circumstances where you are unable to place calls, or inbound calls route directly to voice mail instead of ringing an IP Phone.

If you are unable to change your Primary DNS Server setting to the IP address of your

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server, you run the risk of having intermittent problems with your IP phones, as well as a system outage if you have an internet connection failure.  Some system administrators desire to use an existing local DNS server because of host names maintained by a Windows Active Directory server.  This objection can be overcome by still using the

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server as your primary DNS, but setting your Windows server as a DNS forwarder so that the functionality of your current DNS service remains 100% intact. See below.

Configuration

On many smaller networks, the router or firewall handles DHCP (IP address assignments).  On the other hand, if you have a Windows Domain Controller or other third-party DHCP server, see the appropriate section further on.

On the router/firewall:

1. Log in to your router's web interface.*

2. Find the DNS settings, usually in the local area network or Internet settings area. (see the screenshot below)

3. Change the first DNS server to the static IP address of the PBX on your local area network.  (for example, 192.168.1.10)

4. Secondary and tertiary DNS servers, if any, should remain set to public DNS.  (e.g. the DNS servers your ISP gives you, or 8.8.8.8 and 4.2.2.2)

On the PBX itself:

1. Go to the Options: Network tab on the Web Admin Panel.  Alternatively, hook a keyboard and monitor to the PBX to set up the static IP and DNS (refer to the Installation guide for more information).

2. Make sure that the PBX is configured to use public DNS servers.  If you need suggestions and you're in the U.S., 8.8.8.8 (Google DNS) and 4.2.2.2 (Level 3 Communications) are good primary and secondary choices.  Or use those that your ISP supplies.

*-Most routers have a web interface at the router's IP address (e.g. http://192.168.1.1 ).  Refer to your router manual.  The screenshot to the right shows an old Linksys router -->

Open

Tip for remote phones:
Naturally the above information is only applicable if the phones are on the same physical network as the PBX. If remote phones are having difficulty staying registered, consider reconfiguring their router to use a reliable high-performance primary DNS server such as 8.8.8.8 (Google DNS).

Windows Domain Controller

Note that the following additions may not apply to every installation.  This effectively adds a static DNS entry for your server to the Windows Domain Controller.  That way, if a phone asks the Windows Server "What IP address is 's123...ality.com' at?", the Windows DNS can reply back with the IP address, without having to do a slow DNS lookup to the Internet.

Domain Controller Changes

1. Log Into Domain Controller With Administrator Rights.

2. Click On Start, All Programs, Administrative Tools, DNS

3. Once in the DNS (dnsmgmt) control panel please do the following.

4. Maximize the "Forward Lookup Zones" Folder. In there you will notice two zones "_msdcs.DOMAIN.local" and "DOMAIN.local"

5. Right Click on the "Forward Lookup Zones" Folder and Select New Zone.

6. On the "New Zone Wizard" click "Next"

7. Set the Zone Type As "Primary Zone" click "Next"

8. Make Sure "Active Directory Zone Replication Scope" is set "To all domain controllers in the Active Directory domain DOMAIN.local" click "Next"

9. Zone Name "

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   " (WHERE THE Ns ARE YOUR SERVER ID) click "Next"

10. Dynamic Update "Allow Only Secure Dynamic Updates" click "Next" then "Finish"

11. Find the newly created zone "

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    " double-click on it.

12. On the right side in any blank space (under the existing entries) right-click and select "New Host (A).."

13. Leave the "Name" blank and the set the "IP address" to the static IP address of your

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    server, click on "Add Host"

14. Check (enable) "create associated PTR record" if asked.

These particular directions were developed on SBS2003-R2, but have been shown to work on many later versions.

DHCP-Option 66

For phones to download config updates (such as updated dialplans, new screen names, or new firmware) from the PBX, one must set DHCP-Option 066.  This is only applicable on a network with a Windows Domain Controller or Server running DHCP.Go to Start Menu > DHCP Options > Server Options > right-click and Configure Options > enable (check) boot-server-name 066 > and set it to the IP address of the PBX.  That's it!  When a phone is restarted, it will now check the PBX for configuration updates.If the phones are still failing to get configuration updates, put this into DHCP-Option 066 on the Windows Domain Controller to get the phone to use this particular username and password for provisioning:

(PlcmSpIp/PlcmSpIp is the Polycom factory-default username & password recognized by the local PBX only)

For more information and workarounds, please refer to Setting the Boot Server (in IP Phones).

Reference / other info

Using an existing Server as a DNS Forwarder

(In most cases with Windows Domain Controllers, we recommend using the directions above, under "Domain Controller Changes")  However, if needed:

Please read DNS Forwarder

Using a Local DNS Zone in your existing DNS Server

(This has been deprecated in favor of the directions above.  However, this section has been retained for reference.)

If you already run a local DNS server, and for political or other reasons you are unable to arrange for the

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server to act as your Primary DNS Server, there is one remaining option to provide (almost as much) local reliability. You can define a local zone in your existing DNS server so that

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will resolve to the correct internal IP address for your

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server. The Ns will need to be replaced with your

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server id number. This is the number after “admin” in your username for your

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Admin Panel.

Note that if you use Unix based BIND name server software, this option will work very well. If you use a Microsoft DNS service, there's a possibility of registration trouble, especially if the server is busy, but at least your system will remain running if your internet connection goes down. This approach is known to be relatively reliable, but an address pool and DHCP reservations for the phones is more reliable (so you can tell the phones, specifically, to use the IP address of the PBX as their DNS server).

This is a common fix for Windows Active Directory environments that require that the A.D. be the primary DNS server; here is a link with step-wise instructions on how to do this for your Windows 2003 Domain Controller. Remember:

1. Use "Step 3: Configure the DNS Server" and chose "Secondary Zone" when prompted.

2. For the Master DNS server use the static IP of the

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   .

http://support.microsoft.com/kb/323380

Using Address Pools in a Windows Active Directory

When using a Primary DNS other than the Active Directory server, the DNS requests of workstations and other servers on the network will experience domain-related issues. Alternatively, when not using the

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as a primary DNS, phones will be unable to register.

The best way to resolve this issue is to create a secondary resource pool for all your telephone hardware. Start by assigning DHCP reservations for your phones and set all the IP addresses inside the secondary scope. Then, change the Primary DNS server of the scope to the IP address of

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. This way, DNS requests from the phones can be forwarded to

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and the rest of the network can be handled normally. (For softphones and for HUD registration, it is necessary to hard-code the IP address of

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into the server address, so as not to compromise the DNS requests of the workstation)