How do I eliminate/reduce packet loss in a GRE tunnel?

Aruba Employee
Aruba Employee

Product and Software: This article applies to all Aruba controllers and ArubaOS 2.x and 3.x.


Refer to the exhibit. We have master local setup separated with a router, and a client across the master is trying to access a server across the local controller through a GRE tunnel. No packet loss occurs while we are pinging and we can send/receive files from the server, but the session times out while trying to establish an RDP session.


To troubleshoot this issue, try the following configuration on the controllers:


1) Allow the RDP traffic with port number 3389 in the user role where the user is falling.

(Aruba)(config)# any any Tcp 3389 permit

2) Configure an MTU of 1200 from the default value of 1500 inside the GRE tunnel


To do so, issue the following commands:

(Aruba)(config)#interface tunnel 1

(Aruba)(config)#MTU 1200


One of these troubleshooting steps should resolve the case because a master local setup and a GRE tunnel both exist. So, first an IPsec tunnel will be established between the two controllers, and then a GRE tunnel will be established inside the IPsec tunnel. In many cases, in network setup the MTU size must be reduced because the packet has to travel inside the IPsec and GRE tunnel, and an MTU of 1500 will cause the packets to be dropped.


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‎07-09-2014 02:02 PM
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