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OPERATIONAL DEFECT DATABASE
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FC link throughput is degraded or the link is error disabled by the peer switch. This issue can be confirmed on the peer switch when it logs E_LINK_RXBUF_NOT_AVAIL events for the affected FC interface. These events trigger the peer to send Link Reset to reset the credits on the interface. *slot x show hardware internal fcmac port y link-event* ========= FCP Port# y Link State Machine Event Log ========== MMDDYY HHMMSS usecs Event Current State -------------------- ----- ------------- - - LINK_DIS 091322 175806 610896 (0000) E_LINK_CLEANUP LINK_ACTIVE (0) 091322 175806 610895 (0002) E_LINK_DOWN_OLS LINK_ACTIVE (0) 091322 175806 593261 (0000) E_LINK_IDLE LINK_LRR_RX (0) 091322 175806 589939 (0000) E_LINK_LRR LINK_LR_TX (0) 091322 175806 586900 (0009) E_LINK_RXBUF_AVAIL LINK_LR_TX_WAIT (0) 091322 175806 496456 (0000) E_LINK_RXBUF_NOT_AVAIL LINK_LR_TX (0) 091322 175806 496453 (0022) E_LINK_LINK_RESET LINK_ACTIVE (0) The Nexus 9000 *slot x show logging onboard credit-loss* command shows FCP_CNTR_CREDIT_LOSS events for the affected port connected to the peer switch. If the peer switch error disables the interface, the following syslog messages are seen on the peer switch: *show logging logfile* %PORT-5-IF_DOWN_LINK_FAILURE: VSAN x Interface fc y/z is down (Link failure Link Reset failed nonempty recv queue)
This issue applies to Nexus C93360YC-FX2 and N9K-C9336C-FX2-E switches connected to a peer switch via native Fibre Channel links. Further, the issue only applies when the transmit credits on the Nexus 9k FC interface reaches zero. An FC interface with zero transmit credits is normal when the FC link is oversubscribed or congested.
None.
This issue was caused because the Nexus 9k may send control frames when there are zero transmit credits on an FC interface. The fix will briefly disrupt FCoE traffic and thus is not automatically applied when a switch is nondisruptively upgraded to a fixed release. One of the following steps is required: 1. Disruptively reload the switch using the *reload* command or 2. Remove and reapply the default-fcoe-nq-policy using the following configuration commands: *configure* *system qos* *no service-policy type network-qos default-fcoe-nq-policy* *service-policy type network-qos default-fcoe-nq-policy* *end* *Resolution summary* Nexus 9k no longer sends control frames when there are zero transmit credits on an FC interface.