HOW PACKET DATA TRAVEL FROM EACH NETWORK<br /><ul><li>PC1 build the packet, in the header of the packet there is MAC address source and destination, IP address source and destination. IP address source: 192.168.100.1. IP address destination: 192.168.120.201. IP address and destination are in different subnet and different network. After the packet completed, the packet sent to switch1. Switch1 checks the packet and found the destination address of MAC address is router port E0 (default gateway). Suppose switch1 turn on the first time, all the packet will be received on the other 25 port but it is not processed and will be discarded, except the port for default gateway. The process of switch doing this job is called flooding.
Packet arrived on port E0 of router1. The router checks the packet destination address and found the destination address is on other network (network 3) and it is on different subnet. How does the router determine the data is on different subnet? The interface E0 quickly making calculation, the calculation is called bitwise ending. Bitwise ending is the same with multiplication in decimal or in binary. Bitwise operation is in binary. In this case the 4th octet of IP address destination is converted to binary and the address of port E0 also converted to binary. The router comparing both binary. From this operation it found octet number 3 is different.
After router decides destination is on different subnet, it consult with routing table and found that in order to reach network 3, it must go out from interface S0 and stop there.
The data will not pass to network 3 if static routing has not been configured on router1 and router2. So the administrator must manually configure static routing on router1 and router2.I fthe static routing completed well the port E0 on router1 can be passed to S0 and the packet data on S0 router2 can be passed to port E0 on router2.
Assume the static routing configuration is done. The packet will travel from S0 router1 crossing the WAN and reach the S0 of router2. And then now the packet data will enter port E0 router2 and direct connected to switch3 and then connected to DNS server and finally the data arrived on the server, and then waiting for respond.