Fabric A Analysis
Continuing the investigation on Fab_A_MDS_9710_01 switch, it was found to be a single-switch fabric. As Example 4-27 shows, no output of the show topology command indicated no E_Ports/ISLs on this switch. Therefore, for congestion troubleshooting, there was no need to chase the culprit to another switch. This type of basic information about the fabric design is extremely helpful before investigating congestion symptoms. 继续调查 Fab_A_MDS_9710_01 交换机，发现它是一个单交换机 Fabric。如例 4-27 所示，show topology 命令的输出显示该交换机上没有 E_Ports/ISL。因此，在拥塞故障排除时，没有必要将罪魁祸首追溯到另一台交换机。在调查拥塞症状之前，这类有关 Fabric 设计的基本信息非常有用。
Example 4-27 No output of show topology command indicates single-switch fabric
`show topology`
Next, the troubleshooting workflow followed congestion symptoms from highest severity to lowest severity as explained earlier in the section on Troubleshooting Methodology—Decreasing Severity Levels. The first thing to check was whether there were any interfaces with credit loss events, which can be found using the show logging onboard error-stats command. This command shows instances of credit loss, timeout-drops, and 100ms Tx/Rx credit not available as well as other error counters. 接下来，故障排除工作流程按照前面 "故障排除方法--严重性级别递增 "一节中解释的拥塞症状，从严重性最高的到严重性最低的依次进行。首先要检查的是是否有任何接口发生信用丢失事件，这可以使用 show logging onboard error-stats 命令找到。该命令会显示信元丢失、超时掉线、100 毫秒 Tx/Rx 信元不可用以及其他错误计数器。
As Example 4-28 shows, fc2/45 on Fab_A_MDS_9710_01 switch had many congestion symptoms. 如例 4-28 所示，Fab_A_MDS_9710_01 交换机上的 fc2/45 出现了许多拥塞症状。
Example 4-28 Locating problems on Fab_A_MDS_9710_01 ports using show logging onboard error-stats command
`show logging onboard error-stats`
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