Home » Cisco » 350-080 » Which of the following actions is the best way to start troubleshooting this problem?
You have a customer with an MDS fabric that is experiencing a performance problem. You suspect that the problem is due to a BB credit starvation issue with a host HBA. The customer has both a DS-PAA-2 and a Fibre Channel Analyzer on location. You want to collect a trace and look at the R_RDY flows between the MDS and the host. Which of the following actions is the best way to start troubleshooting this problem?
A. Collect a Fibre Channel Analyzer local brief trace on the MDS and look for missing R_RDYs.
B. Collect a Fibre Channel Analyzer local trace with full detail on the MDS, because the detail is needed to examine the R_RDY flow.
C. Use the DS-PAA-2 and the MDS span feature to capture a trace and examine the R_RDY flow between the host and MDS.
D. Use the Finisar and the MDS span feature to capture a trace because the DS-PAA-2 cannot decode R_RDYs.
E. Break the physical connection between the host and MDS and insert the Fibre Channel Analyzer inline.
Correct Answer: E
Explanation/Reference:
Explanation:
To use a protocol analyzer, you must insert the analyzer in-line with the device under analysis, which disrupts input and output (I/O) to and from the device. This problem is worse when the point of analysis is on an Inter-Switch Link (ISL) link between two switches. In this case, the disruption may be significant depending on what devices are downstream from the severed ISL link.
In Ethernet networks, this problem can be solved using the SPAN utility, which is provided with the Cisco Catalyst Family of Ethernet switches. SPAN has also been implemented with the Cisco MDS 9000 Family switches for use in Fibre Channel networks. SPAN lets you take a copy of all traffic and direct it to another port within the switch. The process is non-disruptive to any connected devices and is facilitated in hardware, which prevents any unnecessary CPU load. Using Fibre Channel SPAN, you can connect a Fibre Channel analyzer, such as a Finisar analyzer, to an unused port on the switch and then SPAN a copy of the traffic from a port under analysis to the analyzer in a non-disruptive fashion.
Reference: http://www.cisco.com/c/en/us/products/collateral/storage-networking/mds-9250i-multiservice-fabric-switch/data_sheet_c78-727493.html