CCNA – Drag and Drop 3
Here you will find answers to CCNA Drag and Drop Questions – Part 3
Remember these rules:
The IP addresses (of source and destination) of a packet never change during the transportation through the network. For example if PC-A wants to send a packet to PC-Z then the source and destination IP addresses of the packet will be the IP addresses of PC-A and PC-Z no matter how many devices they go through.
The MAC addresses, conversely, will change while passing the devices. The source MAC address is the address of the last sender and the destination MAC address is the address of the next device.
When a router boots up, it performs a series of steps, called the boot sequence, to test the hardware and load the necessary software. The boot sequence consists of the following steps:
1) Power on self test (POST): tests the hardware to verify that all components of the device are operational and present.
2) The bootstrap loader in ROM executes: The bootstrap loader is a program in ROM that is used to find where a valid Cisco IOS image is located.
3) If a valid Cisco IOS image is located, it is loaded.
4) IOS loads configuration file. Once the IOS image is loaded, it will search for a valid startup configuration in NVRAM.
5) If a valid startup configuration file cannot be found, the router will load the System Configuration Dialog (sometimes called setup mode). This mode allows you to perform the initial configuration of the router.
If we have many entries matching for next hop ip address then the router will choose the one with most specific path to send the packet. This is called the “longest match” rule, the route with the most bits in the mask set to “1” will be chosen to route packet.
For example, the destination IP address of 10.1.0.14 will match two “ip route” commands:
ip route 10.1.0.0 255.255.255.0 192.168.2.2
ip route 10.1.0.0 255.255.0.0 192.168.3.3
But the first command is more specific (10.1.0.0/24 is more specific than 10.1.0.0/16) so the packet will be routed to 192.168.2.2.
Note: The IP address 10.1.1.10 only matches the second command “ip route 10.1.0.0 255.255.0.0 192.168.3.3”. It does not match the command “ip route 10.1.0.0 255.255.255.0 192.168.2.2” because the third octet is different (10.1.1.10 is different from 10.1.0.0/24).
Administrative distance is the first criterion that a router uses to determine which routing protocol to use if two protocols provide route information for the same destination. It is a measure of the trustworthiness of the source of the routing information. The smaller the administrative distance value, the more reliable the protocol.
In this question, notice that the destination of all routes is 10.1.1.0/24 so we need to use Administrative distance of each routing protocol to specify the priority of each route. Below lists the Administrative Distance default values of popular routing protocols:
+ Directly connected: 0
+ Static route: 1
+ EIGRP (symbolize by “D”): 90
+ OSPF (symbolize by “O”): 110
+ RIP (symbolize by “R”): 120