SPECTRUM alarming on interfaces at both ends of a link when a link goes down (Legacy KB ID CNC TS31303 )

Document ID : KB000052053
Last Modified Date : 14/02/2018
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SPECTRUM alarming on interfaces at both ends of a link when a link goes down

Problem Environment:
SPECTRUM 08.01.00.00
SPECTRUM 09.00.00.00
CallT0000229732
BAD LINK DETECTED
0x10d11
0x1040a
 PortFault Correlation
User has the following scenario:


1. Near end Router A
2. Far end Router B
3. Router A and Router B connected via Point to Point Serial
4. There is a redundant link to the far end Router B
5. Live Link enabled between Router A and Router B
6. Both routers are sending traps to the SpectroSERVER
7. Port Fault Correlation is set to All Connected Ports
8. The link between Router A and Router B goes down
9. SPECTRUM asserts a BAD LINK DETECTED alarm (event 0x10d11) on the interface on Router A and Router B that makes up the link between the two routers


User is expecting the Port Fault Correlation to only assert a BAD LINK DETECTED alarm on the near end router interface and suppress the BAD LINK DETECTED on the far end router interface


The Modeling Your IT Infrastructure Administrator Guide has the following information about configuring Port Fault Correlation:


Configuring Port Fault Correlation


SPECTRUM lets you customize its fault isolation algorithm to resolve the root cause of a network outage to the port level. This is most desirable in cases where a single physical port, such as a Frame Relay interface, supports multiple logical connections to remote devices. If the physical port goes down, SPECTRUM can suppress the alarms on all downstream devices in favor of a single red alarm on the physical interface, thus significantly reducing the number of alarms which need attention. The impact severity and scope of the red alarm on the physical interface will contain all downstream devices, as well as the physical interface.


Port Fault Correlation Options


Use the Port Fault Correlation setting in the VNM model?s Fault Isolation subview to configure port fault correlation.


Disabled Disables port fault correlation. The root cause of a network outage will remain a red alarm on a device model. However, Fault Isolation will still examine all of the device?s connected ports to see if they are all in Maintenance Mode. If so, the alarm on the device model will be suppressed.


All Connected Ports Port fault correlation will run, examining all ports that exist on "up" neighbors which are connected to the down device as possible root causes of the outage. No additional manual configuration is required.


Management Neighbors Only Enables port fault correlation to run but only examine ports which were previously configured manually as management neighbors as possible root causes of the outage.

.
The reason SPECTRUM had asserted a BAD LINK DETECTED alarm on both the near and far end ports of the link was because it received a Link Down trap from both devices. Since SPECTRUM did not lose contact with the far end router because of a redundant link, SPECTRUM was able to receive and process the Link Down trap.
In the above scenario, if there was no redundant link to the far end router;


1. SPECTRUM would have asserted a BAD LINK Detected alarm on the near end router because of the Link Down trap received.
2. SPECTRUM would have lost contact with the far end router
3. SPECTRUM would have checked the status of the linked ports when it lost contact with the far end router because Port Fault Correlation is set to All Connected Ports
4. SPECTRUM would have seen the connected port on the near end router was down
5. SPECTRUM would have suppressed alarming on the far end router
6. The root cause of the suppressed condition on the far end router would have been the BAD LINK DETECTED alarm on the near end router port




(Legacy KB ID CNC TS31303 )