Primary DNS Server Requirement

From Trixbox Pro Help

When setting up your trixbox Pro system you may wonder “Why Do I need to use trixbox Pro as my Primary DNS Server?” There are multiple reasons why. This document describes each of them in technical detail, as well as alternatives if your network is unable to specify the trixbox Pro server as a Primary DNS Server.

The DNS service in the trixbox Pro 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 hostnames 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 trixbox Pro system over your local LAN. By using the trixbox Pro server as a primary DNS server for your network, you eliminate this remote dependency, and allow your trixbox Pro system to operate properly even during an internet access outage.

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

   The trixbox Pro server maintains a local database resource (called a zonefile) containing the IP address of your trixbox Pro server. This allows the trixbox Pro 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 trixbox Pro 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 trixbox Pro system after a registration timeout problem. When you use the DNS service in your trixbox Pro 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 trixbox Pro 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 trixbox Pro 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.

Using an existing Server as a DNS Forwarder

If you have DNS host names that are maintained by an existing DNS server on your network, you may request that the trixbox Support team set up a DNS forwarder configuration for you. This works by allowing the trixbox Pro DNS service to supply answers to queries for all IP Phones, but forwards all other queries to your existing DNS server for further processing. We will need the IP address of your existing DNS server in order to perform this configuration adjustment for you. To contact trixbox Support visit http://support.trixbox.com

Using a Local DNS Zone in your existing DNS Server

This is a common fix for Windows Active Directory environments that require that the A.D. be the primary DNS server

If you already run a local DNS server, and for political or other reasons you are unable to arrange for the trixbox Pro 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 trixbox Pro server so that sNNNNNN.trixbox.fonality.com and sNNNNNNx.trixbox.fonality..com resolve to the correct internal and external IP addresses for your trixbox Pro server respectively. The NNNNNN will need to be replaced with your trixbox Pro server id number. This is the number after “admin” in your “tbadminNNNNNN” username for your trixbox Pro Admin Web Interface login.

Note that if you use Unix based BIND name server software, this option will work very well. If you use a Microsoft DNS service, you may still end up with intermittent registration trouble, but at least your system will remain running if your internet connection goes down. This approach is known to be relatively reliable, but it’s still not as good as using the DNS service built into your trixbox Pro system.

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 trixbox Pro 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 trixbox Pro. This way, DNS requests from the phones can be forwarded to trixbox Pro 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 trixbox Pro into the server address, so as not to compromise the DNS requests of the workstation)