Process routing on a Router
Refer to Part 1 Explore the process packets is moving in the network
Part 2: Process routing on a Router
In this second part of the equipment used in the first ARP Request, and refers to one of the tasks of the Network Router is connected together, find your way to the Packet
The lattice with 2 network 172.16.0.0 network 192.168.1.0 and only through a router. (Figure 1)
Figure 1: The network Topo
Once we have set the IP address and port no shutdown for F0/0, F0/1, S0/ 2/1, S0/2/0 immediately routers build their routing tables with the Network it is connected. (See Figure 4)
Now we jointly explore Router and the device works like, what protocol used to communicate with each other.
1. The machine performed PC0
Ping uses ICMP protocol operates at Layer 3 (network) of the OSI model, while the machines want to transfer data to another MAC address, so how to know the MAC address of 192.168.1.2 is the machine much to the media now?
PC0 see IP Source = 172.16.1.1 172.16.0.0 network of
Destination IP = 192.168.1.2 attached to ping 192.168.1.0 network
PC0 self PC0 not know that the same network with PC2, so be sure to ask to DEFAULT GATE is configured on PC0. So in the process of sending ARP Request, the destination IP address = IP default way (IP F0 / 0 router)
Meanwhile, PC0 initialization protocol ARP request to find the MAC address of the IP 192.168.1.2 as follows
Figure 2: The fields in the ARP Request and Frame
We see in Figure 2: Target IP = IP default gateway.
School Source MAC: The MAC address of Pc0
And the process takes place at the switch (same as in part 1)
And the frame is pushed out all ports, but only f0/0 of router’s MAC answer f0/0 for PC0
Then get MAC PC0 of f0/0 and proceed to perform PING 172.16.1.1
+ In the router (routing process takes place how)
When the router receives the bit sequence, it moved into the frame and then go into the packet.
Here identify the destination IP Router in Packet that PC0 want Ping = 192.168.1.1, 192.168.1.0 IP network has
Figure 3: The field of IP.
Packet Router is going to turn this port (f0/1, s0 /2/0, s0/2/1) now?
The process of comparing the information to the destination network with router table (this table is called the routing table, in this case, the router table with the following information when using the command: SHOW IP ROUTE
(Figure 4: The routing table of the router)
Router 192.168.1.0 network of route found in Table 3, and this line is connected to the port F0/1. Thus router has the task to identify the packet gateway due to its routing table.
Next, the router how to send the packet to the correct destination computer (192.168.1.2) now?
Router to use the ARP request to find the MAC of 192.168.1.2 and similar to 1, only the 192.168.1.0 network PC2 in return for the router MAC.
And thus was able to send Packet Router PC2 according to MAC has.
So when the network is not directly connected to one router that connects through multiple routers, why?The router may not be so easy? The answer is no, then the router itself can not identify the network away from it, but it needs an administrator to provide input to the router so that it build routing tables.
(The following article we learn about the protocols construct the routing table on Router)
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