High CPU utilization with OSPF

Unanswered Question
Dec 11th, 2009
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We have a Cisco 3845 router with OSPF running on GRE interface Tunnels (nb : 88).

There are also GRE/IPSEC interface tunnels (nb 88) with no routing protocol running on them. The pysical support is VSAT.

We encountered 3 times high CPU utilisation (above 90%) related to the OSPF process in a period of 3 weeks). Each time, it happened about 15 minutes after a large number of GRE/IPSEC tunnel interfaces went down in a small interval (a few-seconds).

IOS is 24-15.T3.

Here is the configuration of a GRE/IPSEC interface :

interface Tunnel247
description *** VTI VPN VSAT Secours Ag 47 ***
bandwidth 128
ip address
keepalive 5 3
tunnel source
tunnel destination
tunnel mode ipsec ipv4
tunnel protection ipsec profile VTI-PROFILE

Any idea what is going wrong ?

Thank you in advance.

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janbouma Fri, 12/11/2009 - 10:50
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Please collect the logs, they give us a clue what went wrong.

Make sure you do not have a recursive tunnel as described here:

The "%TUN-5-RECURDOWN" Error Message and Flapping EIGRP/OSPF/BGP Neighbors Over a GRE Tunnel


In that case the tunnel participates in the routing process and it learns the destination of the tunnel through the tunnel interface.




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