Packet drop on GRE tunnel

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Dec 7th, 2006
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I have a 3845 connecting to a 2811 through GRE tunnel. The GRE tunnel from the 3845 will pass through a ASA5520 to encrypt the GRE tunnel into an IPSec tunnel terminated on the 2811.


Occassionally, there is a drop to the tunnel interface independent of load of the tunnel. It is not a lot of drop however there is constantly 3-5 packet drops per minute.


I have checked the Loopback10 and the Ethernet interface and there is no packet drop from any interface. Traffic seems to be behaving properly however interfaces showing drops and not sure what is being dropped.


Is there anyway to find out what causing the drop?

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rafaelgarcia Thu, 12/07/2006 - 14:28
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Hi,


Everything seems to be fine with your configuration. The only thing I will suggest you to configure are the keepalives. This a very important detail when configuring GRE tunnel.


http://www.cisco.com/en/US/customer/tech/tk827/tk369/technologies_tech_note09186a008048cffc.shtml


Do you have any traffic monitoring tool for the interface? Is the physical interface displaying drops as well?


Have you looked at the logs when you get the drops in order to see if there is any log that might help?


Could you post the output of the physical interface related to these tunnels?

Let me know if it helps.


Andrew Chan Fri, 12/08/2006 - 07:48
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I have enabled keepalive on the tunnel interface and it does not help. Actually, the log did not show there is any interface shutdown or lost of routing neighbour relationship. The physical interface does not show any drop either.



Edison Ortiz Fri, 12/08/2006 - 11:22
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You have QoS enabled on that interface, can we see that portion of the config ?

Andrew Chan Fri, 12/08/2006 - 12:16
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You can exclude the QoS configuration. I have checked the service policy and there is no packet drop there and I have even tried to remove QoS completely and the problem still exists.



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rajivrajan1 Fri, 12/08/2006 - 21:46
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give an extended ping , show route and detailed config

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