The switch has diagnostic features available with Enterprise Device Manager (EDM) and Command Line Interface (CLI). You can use these diagnostic tools to help you troubleshoot operational and configuration issues. You can perform such tasks as configuring and displaying log files, viewing and monitoring port statistics, tracing a route, running loopback and ping tests, and viewing the address resolution table.
Traceroute determines the path a packet takes to reach a destination by returning the sequence of hops (IP addresses) the packet traverses.
According to RFC1393, traceroute operates by: "sending out a packet with a time-to-live (TTL) of 1. The first hop then sends back an ICMP error message indicating that the packet could not be forwarded because the TTL expired. The packet is then resent with a TTL of 2, and the second hop returns the TTL expired. This process continues until the destination is reached. The purpose behind this is to record the source of each ICMP TTL exceeded message to provide a trace of the path the packet took to reach the destination."
Ping is a simple and useful diagnostic tool to determine reachability. When you use ping, the switch sends an ICMP echo request to a destination IP address. If the destination receives the packet, it responds with an ICMP echo response.
If a ping test is successful, the destination is alive and reachable. Even if a router is reachable, it could have improperly working interfaces or corrupted routing tables.
Use trace commands to provide detailed data collection about software modules on the switch. The trace toolset can be used to trace multiple modules simultaneously and provides options to specify the verbosity level of the output.
You can enable trace logging through the boot config trace-logging flag.
Caution
Risk of traffic loss
Using the trace tool inappropriately can cause a CPU lockup conditions, loss of access to the switch, loss of protocols, and service degradation.
Tip
While these occurrences are uncommon, when using the trace level tool, minimize this risk. The following actions are:
In situations where trace data is required concurrently from multiple modules, consider troubleshooting during a maintenance window if feasible. Consider a maintenance window period if the switch is stable but CPU utilization is high and CPU traces (example trace levels 9 and 11) are required to diagnose the cause.
Run trace commands from the console port when the CPU utilization is already high. While you can enable or disable tracing when directly connected to the console port.
Activate tracing on one software module at a time.
Initially activate tracing at lower verbosity settings (that is, 2 rather than 3). Increase to verbosity level 3 or 4 only if required, and after level 2 runs safely.
Avoid leaving traces active for extended periods of time. For high CPU utilizations, a few seconds (typically less than 5 seconds) is generally sufficient to identify the cause for sustained high CPU utilization.