Let’s change that using the following configuration: interface FastEthernet0/2ĭoes this resolve the problem or is there still more? Let’s find out: Let’s check the running configuration to view the configuration on that interface:Īh, so some naughty person (*read me) has moved that port from VLAN 1 to VLAN 10. The next output, however, reveals something: All ports are in the default VLAN 1 except port Fa0/2. The first output snippet shows that the interface is up/up, meaning it’s probably not a Layer 1 issue. We will use commands such as show interface, show vlan brief and show run. In this step, we will check things like the state of the port (up or down), its VLAN membership, its switchport mode, etc. The next device to check is the switch to which the device is connected to. Since we are using Packet Tracer, this step will not apply. This is where understanding comes in: Since both hosts (and also the EDGE-RTR) are on the same subnet of 192.168.10.0/24, then the wrong default gateway is not the reason why Host1 cannot communicate with any other device on the LAN.Īt this point, you want to make sure that the device is properly connected to the network, i.e., check if the network cables are wired or check wireless network connection. So Host1 has the correct IP address even though the default gateway is wrong. Hint: On a Linux computer, you will use the ifconfig command instead of ipconfig. Since this is a network problem, what we can do is to check that the IP settings on the host are correct: This tells us that we can focus our efforts on Host1’s connectivity issue. Here we see that Host2 can access the EDGE-RTR but Host1 can’t. In our own case, another device on the LAN is the EDGE-RTR with IP address of 192.168.10.1 so let’s test from each device: One way we can do this is to test whether each device can reach any other device on the LAN (apart from each other).
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Now we need to isolate whether the problem is with both devices or just one of them. Note: It is assumed that you have studied the lab setup and that you are familiar with the different IP addresses. In this type of scenario, you usually have access to the computer that is experiencing issues and one of the easiest things to kick your troubleshooting off with is Ping. It is always best not to assume that the user is really experiencing the issue and to see if you can replicate it yourself. When did this problem start? What changed on the network that could have caused the problem? In a real-world scenario, you will want to ask questions such as: The most basic troubleshooting scenario you will get as a network engineer is that a computer cannot connect to the network e.g., the user is unable to access some company resource or the Internet. On the other hand, if you are troubleshooting why two routers are not forming EIGRP neighbor adjacency, then you will use another method – one that is specific to EIGRP like checking K-values, and so on. For example, if you are dealing with Layer 3 (IP) forwarding, you probably want to start with understanding the traffic flow: How is traffic supposed to flow from device A to device B? When you’ve got this, then you want to start analyzing why traffic is not flowing that way for those devices and continue drilling down until you find the issue. That being said, there is no one-size-fits-all method for troubleshooting and the method you use will differ from scenario to scenario. As a result, we fumble about with different tools and methods in a brute-force manner instead of taking a step back to understand what is going on. We sometimes make the mistake of jumping into troubleshooting without first trying to understand the problem. Troubleshooting is an art that requires great analytical skills and an understanding of how things work. Trblsht_netwk_conn_final.pkt: This Packet Tracer file contains the lab with the issues resolved.