I have been working towards my CCNA certification. Here is a major topic covered in the exam but not in the books.
Its all about what is in a Packet header. Questions about the packet header are about what IP address would be in the host packet sent to the reciver and visa versa. It would also cover Destination and source IP and MACs.
A sample question is: If host A is sending a packet to Host B and in between them is a router and two switches what information will be in the header of the packet sent by Host A? The answer is The MAC address of the interface on the router facing Host A and the destination IP which is from Host B.
A tricky part of these questions is the fact it sorta switches on you when you look at it from the other end. Take this as an example: If host A is sending a packet to Host B and in between them is a router and two switches what information will be in the header after the Router? Answer: the MAC address of the interface you just left and the IP address of the Host.
To figure out these problems is simple. the source MAC is always the next hop unless you are sending it to the the actual host, then it is the interface you just left. The destination MAC is always going to be the Host you are sending to. The Destination IP is always going to be the IP of the Host. SO the Source IP has to always be from the Source.
It seems quite simple when you get the naming right. Take this part of the test slow and you will do just fine!
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