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Vâng, đó là một kéo, nhưng nó không phải là bất hợp pháp. Nó là một trong của mặt nạ mạng con khó khăn nhất bạn có thể chơi với, mặc dù. Và tệ hơn, nó thực sự là một subnet thực sự tốt để sử dụng trong sản xuất, bởi vì nó tạo ra hơn 500 mạng con với 126 host cho mỗi subnet hỗn hợp một-đẹp. | Subnetting Class B Addresses 101 Practice Example 3B 255.255.255.128 25 Oh no This one s got to be illegal right What type of mask is it Don t you wish it were illegal Well it s a drag but it s not illegal. It is one of the hardest subnet masks you can play with though. And worse it actually is a really good subnet to use in production because it creates over 500 subnets with 126 hosts for each subnet a nice mixture. So don t skip over it Cisco thinks it s nice too 172.16.0.0 Network address 255.255.255.128 Subnet address Subnets 29 - 2 510. Hosts 27 - 2 126. Valid subnets Okay now for the tricky part. 256 - 255 1 2 3 and so on for the third octet. But you can t forget the one subnet bit used in the fourth octet. Remember when I showed you how to figure one subnet bit with a Class C mask You figure this the same way. Now you know why I showed you the 1-bit subnet mask in the Class C section to make this part easier. You actually get two subnets for each fourth octet value hence the 510 subnets. For example if the third octet is showing subnet 3 the two subnets would actually be 3.0 and 3.128. Broadcast address for each subnet Valid hosts The following table shows how you can create subnets valid hosts and broadcast addresses using the Class B 255.255.255.128 subnet mask the first seven subnets are shown and then the last subnet Subnet 0.128 1.0 1.128 2.0 2.128 3.0 3.128 . . 255.0 First host 0.129 1.1 1.129 2.1 2.129 3.1 3.129 . . 255.1 Last host 0.254 1.126 1.254 2.126 2.254 3.126 3.254 . . 255.126 Broadcast 0.255 1.127 1.255 2.127 2.255 3.127 3.255 . . 255.127 Subnetting in Your Head Class B Addresses You re probably wondering if I am nuts about now. Subnet Class B addresses in your heads If you think easier equals crazy then yes I m a few sails short but it s actually easier than writing it out I m not kidding Let me show you how Question What subnet and broadcast address is the IP address 172.16.10.33 255.255.255.224 a member of Answer 256 - 224 32. 32 32 64. .
