Chapter 8: Subnets and VLAN

CIDR (Classless Interdomain Routing)

Provides additional ways of arranging network and host information in an IP address. Takes network ID / host's IP and follows it with a forward slash (/), followed by number of bits used for network ID. Example: 192.168.89.127/24. -24 = number of 1s in subnet mask and number of bits in network ID. AKA CIDR Block

Subnets

The process of creating network segments. Dividing the pool of IP addresses into groups/subnets. Benefits: - Documentation easier to manage. - Easier to resolve network issues - Easier to manage routers

Network Segmentation

When a network is segmented into multiple smaller networks. - Traffic on one network is separated from another network, each network is its own broadcast domain. Enhance security, improves performance, simplifies troubleshooting Commonly segmented according to: - Geographic location - Departmental Boundaries - Device types

DHCP (Dynamic Host Configuration Protocol)

A centrally managed DHCP server can provide DHCP assignments to multiple subnets with the help of DHCP relay agent. Routers, firewalls, or layer 3 switches receives DHCp requests from clients. Layer 3 device creates a message of its own + routes transmission to the specified DHCP server in different broadcast domain. DHCP server notes relay agent's IP, assigns DHCP client an IP on same subnet

VLSM (Variable Length Subnet Mask)

Allows subnets to be further subdivided into smaller and smaller groupings until each subnet is about same size as needed IP address space. To create VLSM subnets: -Create largest subnet first, then next largest, etc. Ensures that largest subnet gets size it needs, smallest gets size it needs.

Subnetting Method

IPv4 address divided into 2 parts: - Network ID, host ID Subnet mask is used so devices determine which part of IP is network ID and which is host ID. - Number of 1s in subnet mask determines bits in IP address that belong to network ID. Now called classless addressing. Borrows bits that would represent host info, use those bits to represent network info.