A request to allocate an ephemeral port number from the global UDP port space has failed due to all such ports being in use

Such a long title of error message, I got this error on the Win Server 2012, The server is running for more than 2 years and suddenly all my apps is hang.

The first things we want to check is what is the UDP Port is currently using there is 2 ways to check it.
1. Is using TCPView
2. Is using Command Prompt (netstat) it.

Open the Command Prompt “netstat -anob -p UDP > 20150414_1521.txt” It will save in this file.

We will see there is alot of list of “Dnscache” which is using PPID 3312

[svchost.exe]
UDP    [::]:49656             *:*                                    3312
Dnscache

Moving forward we want to know what is the PPID 3312.
tasklist /svc /fi “pid eq 3312”

svchost.exe 3312 CryptSvc, Dnscache, LanmanWorkstation,
NlaSvc, WinRM

Based on this article it said to turn off the LLMNR Listener, on the last comment

https://social.technet.microsoft.com/Forums/en-US/89364046-7fd1-4c20-bab0-f0138447901f/port-exhaustion-with-dnscache?forum=winserverPN

From what we capture the network traffic we saw that .48 is calling LLMNR destination 224.0.0.252 which is also state in this article:

http://www.schoolleader.com/Documentation/Disabling_LLMNR_Causing_Slow_Networks.pdf

To fix this issue I use the last article “Disabling LLMNR Causing Slow Network” and it work.

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