CCNA – Drag and Drop 2
Here you will find answers to CCNA Drag and Drop Questions – Part 2
A simple way to find out which layer is having problem is to remember this rule: “the first statement is for Layer 1, the last statement is for Layer 2 and if Layer 1 is down then surely Layer 2 will be down too”, so you have to check Layer 1 before checking Layer 2. For example, from the output “Serial0/1 is up, line protocol is down” we know that it is a layer 2 problem because the first statement (Serial0/1 is up) is good while the last statement (line protocol is down) is bad. For the statement “Serial0/1 is down, line protocol is down”, both layers are down so the problem belongs to Layer 1.
There is only one special case with the statement “…. is administrator down, line protocol is down”. In this case, we know that the port is currently disabled and shut down by the administrators.
The question asks us to “begin with the lowest layer” so we have to begin with Layer 1: verify physical connection; in this case an Ethernet cable connection. For your information, “verify Ethernet cable connection” means that we check if the type of connection (crossover, straight-through, rollover…) is correct, the RJ45 headers are plugged in, the signal on the cable is acceptable…
Next we “verify NIC operation”. We do this by simply making a ping to the loopback interface 127.0.0.1. If it works then the NIC card (layer 1,2) and TCP/IP stack (layer 3) are working properly.
Verify IP configuration belongs to layer 3. For example, checking if the IP can be assignable for host, the PC’s IP is in the same network with the gateway…
Verifying the URL by typing in your browser some popular websites like google.com, microsoft.com to assure that the far end server is not down (it sometimes make we think we can’t access to the Internet). We are using a URL so this step belongs to layer 7 of the OSI model.
To remember which type of cable you should use, follow these tips:
– To connect two serial interfaces of 2 routers we use serial cable
– To specify when we use crossover cable or straight-through cable, we should remember:
Group 1: Router, Host, Server
Group 2: Hub, Switch
One device in group 1 + One device in group 2: use straight-through cable
Two devices in the same group: use crossover cable
For example: we use straight-through cable to connect switch to router, switch to host, hub to host, hub to server… and we use crossover cable to connect switch to switch, switch to hub, router to router, host to host… )