dwight reifsnyder

1 Session #: 706

Dwight Reifsnyder

Virtual LANS

Session #: 706

What’s the Point? Why Bother?

“IEEE 802.1Q tagging (VLAN) is a useful method of managing VoIP traffic in your

LAN.

Avaya recommends that you establish a voice VLAN, set L2QVLAN to that VLAN and provide voice traffic with priority over

other traffic.”IP Phones LAN Admin Guide, Feb 2007

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EYAWTK – Session Overview

• Provide a basic understanding of VLANS

• Discuss IP phone VLAN implementation

• We might accidentally learn some other useful information if we are not careful

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Broadway Suites

• Service Provider for downtown Boulder office buildings, including Executive Suites

• Multiple, diverse businesses in one space• Fortune 500 services on a small company

budget

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Broadway Suites

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What is a Virtual LAN?

• A virtual LAN, commonly known as a VLAN, is a method of creating independent logical networks within a physical network.

• Virtual LANs operate at Layer 2 (the data link layer) of the OSI model.

Wikipedia

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Background – The 7 layer burrito

OSI Model

Squishy, not specific

VLANs are in Layer 2

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What Lives at Layer 2?

• Software – Ethernet Protocol

• End Points• Ethernet Hubs• Ethernet Switches

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L2 Hardware – Endpoints

• Phones and PCs are multi layer devices

• We will talk about them at layer 2 today

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L2 Hardware – Network Hub

• Network Hubs – • broadcast traffic• not very efficient

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L2 Hardware – Network Switch

• Network Switches –• Starts like a hub• Gradually directs traffic

to specific ports instead of broadcast

• How do they do that?

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Detour - L2 MAC Addresses

• Like a VIN Number on a car

• Unique to each and every network device

00-07-E9-55-64-4D

• MAC addresses are used to identify the sender and recipient of an ethernet packet

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Network Switch

• Stores MAC addresses and associated port numbers in a table

• Makes network more efficient!

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Evolution - Managed Switches

Have a user console that can show -• If a port is connected or not• Port speed (10MB, 100MB, 1000MB)• MAC address table• Calls out with alarms

• Best solution for Administrators• Cost more $$$$$!

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Segregation – Sorry Dr. King..

• Sometimes we need to have departments separated – • HR, confidentiality• Marketing, high bandwidth usage• Operations

• Each department needs its own LAN

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Segregation – The Old Way

• Multiple Managed Network Switches

• Costly • Complex

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Segregation – The New Idea

• Multiple MAC Address Tables

• One switch, divided into 'Virtual LANs‘

• Great idea, how would it work?

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Detour - RFCs (secret recipes)

• Request for Comments

• Internet Engineering Task Force (IETF)

• Institute of Electrical and Electronics Engineers (IEEE)

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Some Common RFCs

802.1a,b,g,etc Wireless Ethernet (WiFi)

854 Telnet

802.1x Network Access Control

1719 Private Class IP numbers

821 SMTP (Simple Mail Transport Protocol)

1939 POP3 (Post Office Protocol 3)

802.3AF Power Over Ethernet

2131 DHCP (Dynamic Host Configuration)

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RFC 802.1q - VLANs

• Defines how to segregate a single L2 network switch into multiple “virtual' LANs or networks with multiple MAC tables

• One managed network $witch can now serve multiple departments without losing security or performance

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Layer 2 Switch with VLANs

• Logical evolution from switching table

• Port based VLAN identification – every port belongs to a VLAN

• Separate broadcast domains

VLAN 1 – OperationsVLAN 2 – Human ResourcesVLAN 3 – Marketing

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VLANs Across Switches

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VLAN Tags – Don't Lose my Bag

• DEN

• CHI

• NYC

• ELM

• SAT

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VLAN Tags – Ethernet Packets

• Ethernet packet fields• Header• Payload • End

• VLAN tagging information is added to the header, making it slightly longer

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VLAN Trunking Across Switches

The ports which join the switches are defined as belonging to native VLAN and a secondary VLAN. The

secondary VLAN sends ‘tagged’ packets so they can be segregated

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Read you loud and clear…

• VLAN compliant devices can accept tagged or untagged packets

• Packets without tags stay in the native VLAN (port based VLAN)

• Packets with tags go into the VLAN defined by the tag (if that VLAN is allowed on that port)

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Eh? What was that?

• Non VLAN compliant devices discard tagged packets –

they have an invalid header length!

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What Devices Read Tags?

• VLAN compliant switches

• VLAN compliant IP phones

• Microsoft Windows ? X

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Review - Who Sends Tags?

Devices are all in Port Based VLANs – no tagsTrunk between switches must send and receive tags

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802.1q VLAN Port Parameters

• Native VLAN (port based VLAN)

• Secondary VLANs

• Tagging

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IP Phone Deployment

• Avaya suggests that phones should always be in their own VLAN

• Increases security • Cuts down on broadcast traffic• Increases voice quality• Makes troubleshooting easier

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VLAN Deployment Options

2 VLANs, 2 Ports

2 VLANs, 1 Port!

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IP Phones have a Network Switch!

2 VLANs, 1 Port!

The phone contains aVLAN compliant

3 port network switch!!

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Detour – Phones & DHCP & VLANs

• DHCP is an ethernet broadcast request used by devices to get an IP number

• Broadcast packets do not cross VLANs

• Each VLAN needs its own DHCP Server

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Detour – Phones & DHCP & VLANs

• On bootup, the phone sends a DHCP request in the native VLAN (port VLAN)

• The phone is notified if there is a specific voice VLAN

• The phone sends a new DHCP request with the correct VLAN tag

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Review – Who Sends Tags?

The green VLAN is the native VLAN for both network switch ports

The blue VLAN is a secondary VLAN for both network switch ports

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Broadway Suites, 100+ VLANs1942 Broadway

1877 Broadway

1800 Broadway 1301 Canyon

1300 Walnut

1919 14th

(Vectra Bank)

1801 13th

LEGENDSM Fiber (LX)MM Fiber (50 micron SX)

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Do You Understand VLANs?

• You don't really understand something unless you can explain it to your grandmother...

Albert Einstein

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Final Reminders

• Please remember to turn in session evaluations

• The session number is: 706

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Thank YouThank You