user manual

Table Of Contents
4-2
Cisco Active Network Abstraction Fault Management User Guide, Version 3.6 Service Pack 1
OL-14284-01
Chapter 4 Advanced Correlation Scenarios
Device Unreachable Alarm
Device Fault Identification
When a network element stops responding to queries from the management system, one of two things
has happened:
Connectivity to that device is lost.
The device itself crashes or restarts.
Cisco ANA implements an algorithm that uses additional data to heuristically resolve the ambiguity and
declare the root cause correctly. Refer to the following examples:
Device Unreachable Example 1
Device Unreachable Example 2
Device Unreachable Example 1
In this example, the router (R1) goes down. As a result the links, L2, L3, and L4 go down in addition to
the R1 session.
Figure 4-1 Device Unreachable Example 1
In this case the system will provide the following report:
Root cause—Device Unreachable (R1)
Correlated events:
L2 down
L3 down
L4 down
Device Unreachable Example 2
In this example, the router (R1) goes down. As a result the links, L2, L3, and L4 go down as well as the
R1 session. The router R2, accessed by the link L3 is also unreachable.
Note No link-down alarm is displayed for L3 as its state cannot be determined.
L2
Management connectivity
Physical links
ANA Unit
L1
L3 L4
R1
SW1
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