Cisco MDS 9000 Series Configuration Manual page 184

Congestion Isolation
Figure 3: Traffic Flow When Multiple Targets are Connected
• If in a zone, the zone QoS priority is set to medium and Congestion Isolation is enabled on the switches
in the zone, the traffic with zone QoS priority medium are treated as slow, and Congestion Isolation
routes the traffic to the low-priority VL (VL2). To avoid this situation, set the zone QoS priority to low
or high.
• When a link to a Cisco NPV switch carrying multiple fabric logins (FLOGIs) is detected as a slow device,
all the devices connected to the Cisco NPV switch are marked as slow devices.
• Downgrading from a supported release to an unsupported release is disabled after the Congestion Isolation
feature is enabled. To downgrade to an unsupported release:
1. If cong-isolate port monitor portguard action is configured in a port monitor policy, use the no
2. Use the no congestion-isolation {include | exclude} pwwn pwwn vsan vsan-id command to remove
3. Use the no feature congestion-isolation command to disable the Congestion Isolation feature.
4. Use the no system fc flow-control er_rdy command to reset the flow-control mode to R_RDY.
5. Flap all the ISLs using the shutdown and no shutdown commands.
6. Use the show flow-control r_rdy command to display the ISLs currently functioning in R_RDY
7. Use the show flow-control er_rdy command to display the ISLs currently functioning in ER_RDY
Cisco MDS 9000 Series Interfaces Configuration Guide, Release 8.x
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counter {credit-loss-reco | tx-credit-not-available | tx-slowport-oper-delay | txwait} poll-interval
seconds {absolute | delta} rising-threshold count1 event event-id warning-threshold count2
falling-threshold count3 event event-id portguard cong-isolate command to remove the action
from the policy.
any devices that are manually included or excluded as slow-drain devices.
mode.
mode.
Congestion Detection, Avoidance, and Isolation