How to check if GRE open

Clearapps network inventory
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How to check if IP Protocol 47 (GRE) and TCP port 1723 are open

You use pptpsrv.exe and pptpclnt.exe from Microsoft Windows Support Tools. To use these command lines, run command prompt, type pptpsrv on VPN server and pptpclnt server name or IP on the VPN client.

Here are the result from pptpclnt:

pptpclnt chicagotech.net

Initializing WinSock...
Obtaining host information...
Successfully resolved server's host information

======================================
Enter data to send to server (between 1 and 255 chrs.), then hit enter:
-->hello

Successfully connected to server using TCP port 1723 (PPTP)
Sending data to server

Waiting for a reply to the data which was just sent...
Received a reply. Reply contains the following text:
--->

=================================
Connectivity test to TCP Port 1723 was successful!!!
Closing down socket...
=================================

Creating a socket to test GRE protocol traffic...

Total GRE packets sent = 1
Total GRE packets sent = 2
Total GRE packets sent = 3
Total GRE packets sent = 4
Total GRE packets sent = 5

=====================================
Check server to see if the GRE packets were received successfully
=====================================

Closing down socket

Goodbye!

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