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Re: [Fed-Talk] OS X chatting with DNS server via port 5353
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Re: [Fed-Talk] OS X chatting with DNS server via port 5353




On Mar 15, 2007, at 6:18 AM, Michael wrote:

On Mar 15, 2007, at 8:58 AM, Neal Emerald wrote:

Port 5353 is for multicast DNS - which is part of Bonjour.

Yes, I know port 5353 is Bonjour but why does OS X need to chat with the defined DNS servers as part of Bonjour. It's not looking up hostnames when it's doing this.

Just a side note on Bonjour/multicast that some might find interesting/disturbing.


A while ago I added a second ISP and connected a new Linksys BEFSX41 firewall router with NAT and firewall turned on. I have always felt comfortable with NAT, because any inbound packet not associated with a known outbound session is by default dropped.

Then, to my surprise, while running iTunes someone else's iTunes library kept popping up on my list of music sources. It had me a bit spooked. After spending some time with sniffers and Google, I discovered iTunes used Bonjour, and by default my Linksys router allowed multicast traffic into my network!!

So be careful if you are using Linksys, you might be allowing multicast traffic onto your network, and possibly leaking it out.

Todd

PS. If you are seeing multicast chatter, see if it comes and goes depending on whether iTunes is on.

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References: 
 >[Fed-Talk] OS X chatting with DNS server via port 5353 (From: Michael <email@hidden>)
 >Re: [Fed-Talk] OS X chatting with DNS server via port 5353 (From: Neal Emerald <email@hidden>)
 >Re: [Fed-Talk] OS X chatting with DNS server via port 5353 (From: Michael <email@hidden>)



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