SUBNET Communication Technologies CIS 505 Prepare by Thanantinee Tantivejakul

What is Subnet? n Subnetwork n an identifiably separate part of an organization’s network n the network can be connected to the Internet with a single shared network address

Advantage of Subnet n Hide the internal network organization to external routers and thus simplies routing n Shorter routing tables means faster network transfers n Allows address administration to be decentralized

What is Subnet addressing? n Class A: 0xxx, or decimal. n Class B: 10xx, or decimal. n Class C: 110x, or decimal. n Class D: 1110, or decimal. n Class E: 1111, or decimal. Address Class

127 decimal? n 127 decimal or reserved for Loopback and for internal testing on a local machine n Class D are reserved for multicasting n Class E are reserved for future use

Class determines... n N n N = Network, n = node n Class n Class A -- NNNNNNNN.nnnnnnnn.nnnnnnnn.nnnnnnnn B -- NNNNNNNN.NNNNNNNN.nnnnnnnn.nnnnnnnn C -- NNNNNNNN.NNNNNNNN.NNNNNNNN.nnnnnnnn

Subnet Mask n Save the router having to handle the entire 32 bit address n allow to identify the network and node parts of the address

Example of Class B

CIDR & Supernetting n CIDR = Supernetting n CIDR: Classless InterDomain Routing n To avoid the address space crisis by eliminate class system

Subnet vs. CIDR n Borrow bits from the Host ID portion, which increases the number of bits used for the Network ID portion n Combine multiple Class C networks into blocks rather than dividing them into segments

Supernet 4 Class C networks : : : :

: Supernetted Subnet address : Subnet Mask : Broadcast address

CIDR n Reduced subnet mask notation to a shorthand n From n , Subnet Mask n As /22