DNS

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Finding fast forwarders for your DNS server to speed up internet speeds – John Gamboa

Why do you want the fastest DNS servers listed as DNS forwarders on your domain name server? Mainly, to get your internet experience to speed up. Having slow DNS forwarders can affect how long a browser takes to find and load a web page or to start downloading a file. In bad cases I’ve seen some sites become inaccessible because of bad DNS forwarders. Major sites like Google.com and Yahoo.com were getting “Page cannot be found” errors for an entire office!

There’s a quick way to figure which forwarders to set on your server. First, use a DNS benchmark utility. I’ve been using DNSBench and it’s served me well. It’s a free utility that test numerous DNS servers from your location so you can find and use the fastest ones for your computer and network. Even within a city like San Francisco, different locations will get the best results with different forwarders even inside the same building.

DNSBench-Screenshot-John-Gamboa

Download it from here. It’s self contained so you don’t have to install it, just put it in its own directory somewhere on your computer or external drive and run it. Click on Run Benchmark and wait. It’s best not use the PC as much as you can so it can test the DNS servers better and give you a more accurate result.

Once you get the fastest two or three identified, you can put those as your forwarders on your DNS server. Here is a screenshot of one of my DNS servers forwarders page. I set the priority based on the speed results I got from my DNSBench results. You can get by with 2 or 3 but as you can see from my screenshot, you can put more. You’ll notice that even DNS servers provided by the same companies can have differing speeds. After setting this up for one of my clients and changing the forward queries time out to 1 second – which you have to be careful of because slow internet plus short timeouts can result in the forward query loop because you’re not giving enough time for the request to go out and come back – internet surfing drastically improved.

Hope this helps.

DNS Forwarders John Gamboa

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Apple Mac computers lose connectivity to on-premise Exchange server

Every day we experienced many of our Macs losing their connection to the mail server which happened to be a Microsoft SBS 2008 server. For many months the solution was to connect to the public wireless connection that was OK for the users but it was just a workaround. Connectivity would be sporadic and having the Macs connected to the LAN over the wire and to the public wireless connection wasn’t a good long term solution.

After much troubleshooting I figured out that the configuration of their DNS and DHCP servers was incorrect. Research and testing revealed that Macs use Autodiscover to connect to the Exchange server. Internal DNS didn’t have the autodiscover records required by internal Exchange clients. And it didn’t matter what client – Entourage, Apple Mail, Outlook for Mac – they all lost connectivity quite often and a random times. Once was resolved but adding the proper records there was one other problem.

DHCP was configured to assigned the SBS server AND and external DNS server for DNS. Once that was rectified by setting DHCP to assign just the SBS server as the DNS server and running DNS Bench to determine the fastest DNS servers for the office and setting them as the forwarders, the Macs maintained stable connectivity to the Exchange server. Finally!

Why was this the case? The Macs need Autodiscover records to be set up correctly in DNS. That’s why connecting over public wireless connection worked. The external DNS servers had Autodiscover records set up correctly for external clients. Luckily this worked for their environment as a band-aid. When the internal one wasn’t configured correctly the Macs could never connect to the Exchange server using the internal DNS server to resolve hostnames.

Why was it sporadic? I chalk it up to the sometimes slow DNS name resolution of the SBS server. If it didn’t respond quick enough, it would force the Macs to use the external DNS server for name resolution and would work, but if the SBS server did respond in time, they would lose connectivity.

So fixing both was necessary – DHCP to only assign the SBS server as the internal DNS server and for DNS to be configured with the correct Autodiscover records.

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Domain registrar contact verification – Don’t ignore

If you haven’t already done so, log in to your domain name registrar and verify your contact information. Each registrar’s method is different so you’ll have to Google or talk to your tech support to figure out how to do it if it isn’t obvious. Some registrars like Network Solutions actually pop up a contact verification screen. Some have “Pending verification” next to your domain or domains. Others may not be so conspicuous. Some may have sent out an email a while back that’s waiting for a response. Either way, don’t ignore the contact verification prompts. This is a new ICANN policy this year. Check here and here and here for more information.