Unh-iol Bfc Knowledgebase Vlan-gvrp

8/12/2019 Unh-iol Bfc Knowledgebase Vlan-gvrp

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VLANs and GVRP

Curtis Simonson

Bridge Functions ConsortiumInterOperability LabJuly, 2000


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Presentation Overview

Standards Involved

Bridging Background

802.1Q/1D:

the problem the solution

GVRP

Tagging Frames

Testing It


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The ISO OSI Model


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Standards Involved

IEEE Standard

The Bridge

Standards

(802.1) Most widely

used with the

802.3 MAC

(who doesnt

use Ethernet?)

Bridging is

MACindependent


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Quick Review - Shared Medium

All machines share

the network

Only one machine can

talk at any one time

Distance limitations

Total throughput limit

Collision likelihoodincreased


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Shared Medium (Repeated Network)

All machines share

the network

Only one machine can

talk at any one time Distance limitations

At most 205m.

Total throughput limit

Collision likelihood

increased

Repeaters

End Stations

5m

100m


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Bridging Review

Connects Separate

shared Networks

Frame Translation/

Encapsulation (TokenRing to Ethernet)

Reduces Unicast

Traffic Switches: Allow for

multiple conversations


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Bridging Background

Bridges work at

layer 2 of the OSI

Model

Their primary

function is to

relay frames


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Filtering Database Review

One database contains

MAC addresses,

which port theyre on,

and if theyre active

or disabled

Duplicate MAC

addresses not allowed(the second one would replace the

first)

Entry MAC Addr Port active

1 0800900A2580 1 yes

2 002034987AB1 1 yes

3 00000C987C00 2 yes

4 00503222A001 2 yes5

6

7

8

9

1011

12


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802.1Q - Standard for VLANs

Defines a method of

establishing VLANs

Establishes the

Tagged Frame

Provides a way to

maintain priority

information acrossLANs


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Reasons For Standardizing VLANs

Old implementations could only be defined in

one switch

To connect a VLAN to another network, each

VLAN needed a router port

The only multi-switch VLANs were proprietary:

Cisco: ISL

Bay: Lattisspan 3Com: VLT

Cabletron: SecureFast


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Standards Based VLANs

Includes definition for a new GARP

application called GVRP (GARP VLAN

Registration Protocol)

Propagate VLAN registration across the net

Associate incoming frames with a VLAN ID

De-associate outgoing frames if necessaryTransmit associated frames between VLAN

802.1Q compliant switches


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What are VLANs - Virtual Local Area Networks?

Divides switch into two ormore virtual switches

with separate broadcast

domains

Achieved by manual

configuration through the

switches management

interface Only that switch will be

segmented


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Multiple VLANs in One Switch

Multiple VLANs can be defined on the same switch


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Why VLANs?

Lots of broadcast traffic wastes bandwidth

VLANs create separate broadcast domains

Microsoft Networking

Novell Networking

NetBEUI

IP RIP

Multicast (sometimes acts like broadcast)

VLANs can span multiple switches and

therefore create separate broadcast domains

that span multiple switches


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More Reasons...

Link Multiplexing

slower speed

technologies share the

high-bandwidth uplink

multiple IP subnets on

one physical link with

layer 3 switching (such

as to connect Morse,

Leavitt and Ocean ifwe were switched

instead of routed)


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And One More Reason...

Security

Traffic is only seen by who it is intended for

example: Two separate VLANs, one for accounting

and one for sales. Sensitive accounting datatransmitted over the network will only be seen by

devices in the accounting VLAN.


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Basic VLAN Concepts

Port-based VLANs

Each port on a switch is in one and only one VLAN (except trunk

links)

Tagged Frames

VLAN ID and Priority info is inserted (4 bytes)

Trunk Links

Allow for multiple VLANs to cross one link

Access Links

The edge of the network, where legacy devices attach

Hybrid Links

Combo of Trunk and Access Links

VID

VLAN Indentifier


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Tagged Frames

4 Bytes insertedafter Destination

and Source

Address

Tagged Protocol

Identifier (TPID)

= 2 Bytes (x8100)

length/type field

Tagged Control

Information

(TCI) = 2 Bytes

contains VID


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Trunk Link

Attaches two VLAN switches - carriesTagged frames ONLY.


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Access Links

Access Links are Untagged for VLANunaware devices - the VLAN switch adds

Tags to received frames, and removes Tags

when transmitting frames.


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Hybrid Links

Hybrid Links - ALL VLAN-unaware devices

are in the same VLAN


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So Far So Good...

So one might ask: how does the Filtering

Database handle VLANs?

Two answers:multiple (distinct) tables: one for each VLAN

one table, with a VLAN column

They sound similar, but it turns out they areVERY different


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1 0800900A2580 1 yes

2 002034987AB1 1 yes

3 0500A1987C00 2 yes

4 00503222A001 2 yes5

6

7

8

9

1011

12

Multiple Tables

Called MFD (multiple

Filtering Databases) or

it might also be called

Independent Learning Each VLAN learns

MAC addresses

independently, so

duplicate MACaddresses are OK as

long as they are in

different VLANs.


1 0800900A2580 1 yes

2 002034987AB1 1 yes

3 0500A1987C00 2 yes

4 00503222A001 2 yes

5

6

7

8

9

10

11

12


1 0800900A2580 1 yes

2 002034987AB1 1 yes

3 0500A1987C00 2 yes4 00503222A001 2 yes

5

6

7

8

910

11

12


1 0800900A2580 1 yes

2 002034987AB1 1 yes3 0500A1987C00 2 yes

4 00503222A001 2 yes

5

6

7

8

9

10

11

12

Each Table is

for One VLAN


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One (Big) Table

Called SFD (Single

Filtering Database) or

Shared Learning

No duplicate MAC

addresses

Asymmetric VLAN

possible

Entry MAC Addr Port active VLAN

1 0800900A2580 1 yes 2

2 002034987AB1 1 yes 2

3 0500A1987C00 2 yes 2

4 00503222A001 2 yes 2

5 080034090478 3 yes 1

6 049874987AB1 5 yes 1

7 0555A1945600 5 yes 3

8 00503222A023 5 yes 2

9

10

11

12


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Independent Learning I

Legacy router

learns MAC

addresses fromboth VLANs

Requires 2 physical

links


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Independent Learning II

VLAN-aware router only needs one physical link


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Problems

Cant combine SFD and MFD switches in

one network

Some switches only do one or the other,and cant be changed

Hybrids of SFD and MFD makes this tricky


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Future Additions

Layer 3 based VLANs

IP traffic on a different VLAN than IPX

Multiple Spanning Trees (one per VLAN)allows for using the disabled links

ATM to IEEE VLAN mapping

Emulated LANs


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GARP (yeah, I know, the world according to thats a new one!)

Generic Attribute Registration Protocol

Standard Defines:

method to declare attributes to other GARPparticipants

frame type to convey GARP messages:

Protocol Data Unit (PDU)

rules and timers for registering/de-registering

attributes


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GARP - how?

A device wants

to declare a

certain attribute

It sends adeclaration

The bridge

receives it and

propagates it

throughout the

network.


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GARP - two devices

A second

device wants to

declare a

certainattribute

Now a path

has been

formed.


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GMRP

GARP Multicast Registration Protocol

Defines a GARP Application (instance of

the generic framework)

Allows devices to declare membership in a

multicast group


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GMRP - multiple devices

Devices declare

membership in a

multicast group

All multicastframes for that

group propagate

only to the proper

devices.


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GMRP - Pros & Cons

Pros:

provides multicasting

that isnt broadcasting

works throughlegacy bridges

allows asymmetric

pruning

Cons:

end stations must

support 802.1p

no interface betweenIGMP and GMRP

(yet)


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GVRP - GARP VLAN Registration Protocol

Disadvantages to Static VLANs

Static VLANs are created via management

Must be maintained by a network admin

Static VLANs must be reconfigured for every

network topology change


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GVRP Simplifies All This!

GVRP creates dynamic VLANs

No manual configuration needed

GVRP is maintained by the devices themselves

Topology change? No problem, GVRP

recreates the dynamic VLAN automatically


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What can GVRP do for you?

Allows the creation of VLANs with a specific

VID and a specific port, based on updates from

GVRP-enabled devices.

Advertises manually configured VLANs to otherGVRP-enabled device. As a result of this the

GVRP-enable devices in the core of the network

need no manual configuration in order to inter-

operate.


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GVRP Info

GVRP is a GARP application that registers

attributes for dynamic VLANs

GVRP deals only with the management of

dynamic VLANs

Everything that you have learned about

static VLAN packet format and

transmission applies


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VLAN Data Frame Format Review

GVRP handles data in the same way as Static

VLANs do.

Header, inserted after the destination and source

addresses, that contains Protocol Identifier and VID


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How GVRP does all this:

The method of advertisement used by

GVRP-enabled devices consists of sending

Protocol Data Units (PDUs), similar to

Spanning Tree BPDUs, to a known

multicast MAC address (01 80 C2 00 00 21)

to which all GVRP-enabled devices listen to

for updates. GVRP advertisement followsthe definition of GARP.


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What do these PDUs contain?

A single PDU may contain several different

messages telling the GVRP-enabled device

to perform a specific action.

Join: register the port for the specified VLAN

Leave: de-register the port for the specified

VLAN

LeaveAll: de-register all VLAN registrations onthat port

Empty: request to re-advertise dynamically

and statically configured VLANs


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Industry Implementation Example

3Com manufactures Network Interface Cards that take

advantage of GVRP

Accessed via the Control Panel (DynamicAccess

)

Extremely easy to configure

Windows screenshot>

Vendors (current):

Cisco Systems, 3Com

and Hewlett Packard

Several others are

developing working

implementations also.


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Example: GARP/GVRP

S

SS

E ERED GREEN

EE

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