Category Archives: Networking

Leveraging OpenSource and Freely Available Technology

Recently I gave a talk at the Annual TABS conference about various OpenSource technologies and how they can relate to operating more efficiently and effectively with special attention to Unix/Linux/OSX infrastructures. I think it went over very well, and I was truly surprised how little of this stuff was used by schools. Especially when everyone is focused on keeping costs down. Many schools spend their money on services and contracts for software instead on great IT people that can be innovative for education, instead they are always putting out fires. So here are the slides : TABS Slides

My Thoughts on mDNS (Bonjour) … and turning it OFF!

Apple Bonjour Icon

Ok so Apple uses mDNS heavily in 10.6 and still quite a bit in 10.5, and it looks like they will keep on increasing it. How ever this is not singular to Apple other platforms now use this as well. For those of you who don’t know this is multicast DNS a.k.a bonjour. This is used to make people’s life easier when connecting devices via the network so that people don’t have to do any complicated configuration or really understand what is going on.

Under the hood a computer running mDNS (which is every Mac that at least is running 10.5) constantly sends outs multicast packets broadcasting itself on your network, bonjour enabled devices are doing the same thing. So my question is why would anyone want their computer constantly broadcasting to anybody that is listening, and oh by the way here is some specific information about me. On the other side take 50 MacBooks place them on a wireless access point … what do you think will happen, and why would any IT department need bonjour (they should know how to configure what ever devices they need)?

Some access points completely shutdown with all the multicast traffic going on, and even if they don’t have any problems why would you want all that useless data on a network. This is what I find really funny, in 10.5 you could just simply shutoff mDNS by taking it out of launchd, this seemed completely reasonable, although I would like to see an easier method for people who are not command line savvy.

sudo launchctl unload -w /System/Library/LaunchDaemons/

Now fast forward to 10.6, issue the same command and mDNS stops running. So far so good, bring up a web page … no dice. That is because Apple now combined DNS with mDNS so if you shut down mDNS you cannot resolve any DNS names!

Instead you have to edit a plist file, here are the instructions:

1. Edit: /System/Library/LaunchDaemons/
2. Add the following key to the end of the 'ProgramArguments' array: <string>-NoMulticastAdvertisements</string>
3. Save and close the file.
4. Stop and Start mDNS or Reboot.

Once you do this you can relish in the fact that no more multicast DNS and no more useless traffic.

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