Chapter 4 Advanced Correlation Scenarios

Generic Routing Encapsulation (GRE) Tunnel Down/Up

Note The GRE Tunnel Alarm Down is supported only on GRE tunnels that are configured with keepalive. When keepalive is configured on the GRE tunnel edge, if a failure occurs in the GRE tunnel link, both IP interfaces of the GRE tunnel will be in Down state. If keepalive is not configured on the GRE tunnel edge, since the alarm is generated arbitrarily from one of the tunnel devices when the IP Interface changes to the Down state, the GRE Tunnel Down alarm might not be generated.

When a failure occurs, the GRE tunnel link is marked orange. When the IP interface comes back up, a fixing alarm is sent, and the link is marked green. The GRE Tunnel Down alarm is cleared by a corresponding GRE Tunnel Up alarm. It will also be cleared when the GRE link is discovered again.

GRE Tunnel Down Correlation Example 1

The following provides an example of a GRE Tunnel Down correlation for a single GRE tunnel.

In this example:

Router 1 (R1) is connected to Router 3 (R3) through a physical link L1.

Router 3 is connected to Router 2 through a physical link L2.

Router 1 is connected to Router 2 through a GRE tunnel.

Figure 4-14 GRE Tunnel Down Example 1 (Single GRE Tunnel)

R1

L1

 

R3

 

GRE tunnel

 

L2

Physical links

R2

GRE tunnel

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When a Link Down occurs on L2, a Link Down alarm appears. A GRE Tunnel Down alarm is issued as the IP interfaces of the tunnel edge devices go down. The IP Interface Status Down alarms will correlate to the GRE Tunnel Down alarm. The GRE tunnel down will correlate to the Link Down alarm.

The system provides the following report:

Root cause—Link down: L2 Router 2 <-> Router 3

Correlated events:

GRE tunnel down Router1:tunnel <-> Router 2:tunnel

IP interface down Router 1:tunnel

IP interface down Router 2:tunnel

 

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Cisco Systems 3.6 specifications GRE Tunnel Down Correlation Example, GRE Tunnel Down Example 1 Single GRE Tunnel

3.6 specifications

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