nơi tôi đến với 0 trong Octet thứ ba và 1 trong Octet thứ tư. Số thập phân có thể giá trị của bất kỳ phạm vi octet từ 0 (tất cả các bit được thiết lập là 0) đến 255 (tất cả các bit được thiết lập để 1). Vì vậy, các địa chỉ IP trong mạng con có thể có tất cả các số 0 trong Octet thứ ba. | PART III Subnetting IP Addresses CHAPTER 10 Now you probably wonder where I came up with the 0 in the third octet and the 1 in the fourth octet. The possible decimal values of any octet range from 0 where all bits are set to 0 to 255 where all bits are set to 1 . So the first IP address in the subnet can have all 0s in the third octet. So why does the fourth position start with 1 Remember I said earlier that the node address could not be represented by octets containing all 0s or all 1s. If the fourth octet was 0 both the node octets the third and the fourth would be all 0s which is used to denote the subnetwork address and so it isn t a legal address for a node. To determine the range of addresses for a particular subnet you take that subnet s starting address and use all the addresses that are between it and the starting address of the next subnet. For example the first subnet will contain all the addresses between and but not including . Table gives the start and end address for the first 10 of the 30 subnets that you created. To figure out the other 20 ranges simply add the increment 8 to the second octet the subnet octet . Table IP Address Ranges for Subnets First 10 of 30 Subnet Start Address End Address 1 2 3 4 5 6 7 8 9 10 187 PART III Routing LAN Protocols CHAPTER 10 TCP IP Primer Why does the end address for each subnet stop at 254 Remember that the node portion of the IP address in this case the third and fourth octet cannot be all 1s or 255 in decimal format . So you can have all 1s in the third octet 255 but can only go to 254 in the fourth octet. How many IP addresses do you lose when sub -netting Be advised that subnetting stealing bits for subnets reduces the number of IP .
