When creating a route between two or more routers, such as RIP, EIGRP or OSPF, you will often encounter network failures. When a network failure occurs, you will choose which command to check at the first time. You can spend Take a few seconds to recall.
So the following troubleshooting commands I shared, I don’t know if they are in the list of the first troubleshooting commands you just recalled.
The following is an example of OSPF. The topology used for troubleshooting in this article will also be the following example:
Ping
The first most commonly used command is ping, ping stands for Packet Internet Groper, it operates at the network layer of the OSI model and uses the ICMP protocol, the ping command is used to test whether there is connectivity between two devices.
For example, PC 1 and PC 2 are connected to routers with IP addresses 10.0.0.2 and 10.0.0.2, to check the connectivity, run the command ping 10.0.0.2 from PC 1.
Show Interface
Displays the current state of the interface (port), including whether the port is open or closed, what IP address is assigned to it, its data transmission mode, etc.
Show IP Interface
Displays the current status of the interface (port), including IP address, broadcast address, and shows whether the port is open or closed.
Traceroute
The Traceroute command traces the end-to-end path of data packets through the Internet, which allows you to trace the exact path data travels in the network.
For example, I want to trace a route between PC 1 and PC 4 which is assigned IP addresses 10.0.0.2 and 40.0.0.2, so running this command on PC 1: traceroute 40.0.0.2 will show the possible routing.
Show Protocols
Displays the current status of the interfaces in the router and their IP addresses, this command is useful if you just want to check the IP addresses of all the interfaces in the router.
Show IP Protocols
This command helps you identify the protocols configured in your router.
Telnet
Telnet is a protocol that allows you to connect to a remote computer (called a host) over a TCP/IP network (such as the Internet), and Telnet commands allow you to access and configure your router through a remote connection.
To connect to the router remotely, run the command telnet Host IP Address(要远程访问的PC的IP地址).
For example, I want to remotely connect to Router 4 from Router 1.
Telnet 3.0.0.2
Show running-config
This is the most important routing troubleshooting command. It will show you all the configurations you have done on your router, it will show all the commands you have run on your router including hostname, ip address, clock frequency and routing.
show IP route
This routing command allows you to check all routes to all destinations.
Show IP protocol database
Show IP protocol database works on EIGRP and OSPF protocols, shows networks assigned to different areas.
I hope this article is helpful to you, and you can use it when you troubleshoot Cisco equipment!