Troubleshooting Four Steps 1.Cisco recommended:
ping loopback address; ping the NIC; ping ping default gateway and the remote device.
1. Open a DOS window and ping127.0.0.1. This is a diagnostic or loopback address, if you get a successful return to Ping, you can identify your IP stack is initialized. If it fails, then your IP stack fails, and you need to reinstall TCP / IP on the host.
2. In the DOS window, IP address, ping the local host. If successful, you can explain your network interface card (NIC) is functioning. If it fails, it indicates a problem with the NIC card. This step does not mean that the network cable is connected to the NIC, which only shows the IP address of the host stack can communicate (through the LAN driver) to this NIC.
3. In the DOS window, ping the default gateway (router). If the ping correctly, a NIC connected to the network and can communicate with the local network. If it fails, it indicates that there is a local physical network problem, this problem may occur in any NIC to a position between the router.
4. If the steps 1 to 3 are successful, attempts to ping the remote server. If normal, it indicates that you can perform IP communication between the local host and the remote server. At the same time, you can be sure that the distal end of the physical network is normal.
Note: Note the IP address given is legitimate.
2. Use the traceroute command
the traceroute (or simply the trace) shows the path of data packets to the remote device. Time to live (TTL) and the time-out limit ICMP error message packets through the Internet to describe a route to a remote host chosen. trace command also displays the number of hops the packet arrives at a remote device passes.
trace (trace command) may be used for the user or privileged mode, the path may be determined which network unreachable router attached should be checked most likely to cause failure of the network machines.
3. Use the debug command
debug command is used for troubleshooting a Cisco IOS executed in privileged mode. It can display a variety of operating systems and their associated router traffic generated and received information, further including any error messages. Do not
Debug can be used in user mode, only the privileged mode
debug operation is considered to be a very high priority, as it will consume enormous resources and routers have been diagnosed with the exchange of data packets. It is not simply the debug tool to use as a monitor, only a short time and only as a troubleshooting tool.
By using debug, you can find out about the network and running software or hardware components opponent both problems.
Because the debug output has a higher priority than other network traffic, and diagnose all command generates more than any other diagnostic output of the command, so it can severely degrade the performance of the router, and even cause the router is unavailable. If the router's CPU utilization has reached more than 50%, not suitable for use debug all command.
4. Use the show processes command:
show processes (or show processes cpu) is a view given router CPU utilization tools. It will list the active processes and ID, priority, scheduler test (state), the use of CPU time, the number of activations such as these processes a lot of data!
When a router to evaluate the performance and CPU utilization, this command is useful, for example, want to perform when debug commands.
The first row shows the last 5 seconds, CPU 1 minute to 5 minutes utilization. In front of the output "CPU utilization for the last 5 seconds" line gives a 2% / 0% of such data. Equal to the total utilization of the first data, second data utilization are given due to the interruption caused runtime.