CCNA Notes

200-301 Exam Prep

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1Networking Devices2Interfaces And Cables3OSI Model and TCP/IP Suite4Intro to the CLI5Ethernet LAN Switching - Part 16Ethernet LAN Switching - Part 27IPv4 Addressing - Part 18IPv4 Addressing - Part 29Switch Interfaces10The IPv4 Header11Routing Fundamentals - Part 111Static Routing - Part 212Life of a Packet13Subnetting - Part 114Subnetting - Part 215Subnetting (VLSM) - Part 316VLANs - Part 117VLANs - Part 218VLANs - Part 319DTP / VTP20Spanning Tree Protocol - Part 121Spanning Tree Protocol - Part 222Rapid Spanning Tree Protocol23Etherchannel24Dynamic Routing25RIP / EIGRP26OSPF - Part 127OSPF - Part 228OSPF - Part 329First Hop Redundancy Protocol30TCP and UDP31IPv6 - Part 132IPv6 - Part 233IPv6 - Part 334Standard Access Control List35Extended Access Control List36CDP and LLDP37NTP - Network Time Protocol38DNS - Domain Name System39DHCP - Dynamic Host Configuration Protocol40SNMP - Simple Network Management Protocol41SYSLOG42SSH - Secure Shell43FTP and TFTP44NAT (Static) - Part 145NAT (Dynamic) - Part 246QoS (Voice VLAN) - Part 147QoS (Quality of Service) - Part 248Security Fundamentals49Port Security50DHCP Snooping51Dynamic ARP Inspection52LAN Architectures53WAN Architectures54Virtualization and Cloud - Part 154Virtualization (Containers) - Part 254Virtualization (VRF) - Part 355Wireless Fundamentals56Wireless Architectures57Wireless Security58Wireless Configuration59Introduction to Network Automation60JSON, XML, and YAML61REST APIs62Software Defined Networking63Ansible, Puppet, and Chef67CCNA Complete Cheatsheet
/VLANs - Part 1
Topic 163 min read

VLANs - Part 1

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16. VLANS : PART 1

WHAT IS A LAN ?

  • A LAN is a single BROADCAST DOMAIN, including all devices in that broadcast domain.

BROADCAST DOMAINS

  • A BROADCAST DOMAIN is the group of devices which will receive a BROADCAST FRAME (Destination MAC : FFFF.FFFF.FFFF) sent by any one of the members.

Image of LAN with FOUR BROADCAST DOMAINS (192.168.1.0 / 24)

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Performance :

Lots of unnecessary BROADCAST traffic can reduce network performance.

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BROADCAST FRAME flooding all our subnets with unnecessary traffic.

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Security :

Even within the same office, you want to limit who has access to what. You can apply security policies on a ROUTER / FIREWALL. Because this is one LAN, PC’s can reach each other directly, without traffic passing through the router. So, even if you configure security policies, they won’t have any effect.

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WHAT IS A VLAN ?

VLANS:

  • logically separate end-hosts at LAYER 2
  • are configured on Layer 2 SWITCHES on a per-interface basis.
  • any END HOST connected to that interface is part of that VLAN

PURPOSE OF VLANs:

Network Performance :

  • Reduce unnecessary BROADCAST traffic, which helps prevent network congestion, and improve network performance

Network Security :

  • Limiting BROADCAST and unknown UNICAST traffic, also improves network security, since messages won’t be received by devices outside of the VLAN

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SWITCHES do not forward traffic directly between HOSTS in different VLANS

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Sending Packets to another VLAN (Routed through R1)

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HOW TO CONFIGURE VLANS ON CISCO SWITCHES

#show vlan brief

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Shows which VLANS that exist on the SWITCH and what INTERFACES are in each VLAN

VLANs 1 (DEFAULT), 1002-1005 exist by default and cannot be deleted (5 VLANs)

HOW TO ASSIGN INTERFACES TO A VLAN

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  1. Use the “interface range” command to select all the interfaces at once

  2. Use the “switchport mode access” command to set the interface as an ACCESS PORT

WHAT IS AN ACCESS PORT?

  • An ACCESS PORT is a SWITCHPORT which belongs to a single VLAN, and usually connects to end hosts like PCs.

SWITCHPORTS which carry multiple VLANs are called “TRUNK PORTS” (more info on TRUNK in next chapter)

  1. Use the “switchport access” command to assign a VLAN to a PORT

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Use “#vlan <#>” to enter Configuration Mode for a given VLAN (this can also create a VLAN)

Use “#name <name>” to configure a NAME for your VLAN

To check your VLAN configuration, use “#show vlan brief”

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Testing VLAN 10

Pinging from PC1 using 255.255.255.255 (FFFF:FFFF:FFFF) floods broadcast packets to R1 and VLAN10 hosts only

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PreviousSubnetting (VLSM) - Part 3
NextVLANs - Part 2