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Should I allow Netbios UDP port 137 out on our primary DNS server??

Should I allow Netbios UDP port 137 out on our primary DNS server??  Could I get an explanation on why this would or wouldnt be needed.  I am just seeing a lot of outgoing traffic on port 137.

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If your network is working well without it, keep it blocked.
mkurtzhalsAuthor Commented:
Could I please get an explanation why my DNS server would be attempting to send all this UDP traffic out?
If you want to minimize upd traffic :

1. Disable service "NetBios TCP/IP helper"
2. Check Advanced properties of TCP/IP connection and Disable Netbios.

Chris DentPowerShell DeveloperCommented:


You'll need the TCP/IP NetBIOS Helper if you want to use File and Printer Sharing on the server. But I'd agree with disabling NetBIOS in the TCP/IP properties, I never liked it.

The traffic in question is NetBIOS-NS, NetBIOS Name Service. It's responsible for all sorts, including registering names on the NetBIOS network.

It's nothing to do with DNS so don't feel that blocking it will impact the functionality of your DNS Server.

It's also unlikely to be malicious traffic if it's Outbound, if you've curious about what's in those requests I'd recommend putting a Packet Sniffer onto the machine. I like WireShark for such tasks, you can grab that here:



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