© 2003, Cisco Systems, Inc. All rights reserved. FWL 1.0—6-1 111 © 2003, Cisco Systems, Inc. All rights reserved

© 2003, Cisco Systems, Inc. All rights reserved. FWL 1.0—6-1111© 2003, Cisco Systems, Inc. All rights reserved.

© 2003, Cisco Systems, Inc. All rights reserved. FWL 1.0—6-2

Module 6

Bridges


Overview

This chapter discusses wireless bridges as a means of connecting LANs. Bridges are used to connect two or more wired LANs to create one large LAN.


Learning Objectives

•Determine the feasibility of installing a wireless bridge link.

•Explain why a wireless bridge may be a better solution than other alternatives.

•Determine the maximum distance that can be achieved using wireless bridges with given antennas and extension cables.

•Identify steps necessary to protect a wireless bridge installation against a lightning strike.


Key terms

• Root bridge

• Non-Root bridge with clients

• Non-Root bridge without clients

• Repeater AP

• Root AP

• Site-Survey client

• Installation mode


Bridge Connection


Bridging Defined

Bridges are used to connect two or more wired LAN’s, usually located within separate buildings, to create one large LAN.


Technology Comparisons

TechnologyTechnology

Recurring CostRecurring Cost

Installation Cost

Installation Cost

Monthly Cost (USD)Monthly Cost (USD)

Dialup or 56K

Dialup or 56K

$25 to $50$25 to $50$0 to $250$0 to $250

Barriers to ImplementBarriers to Implement

Remote locationsRemote

locations

Cable/DSLCable/DSL $0 to $250+$0 to $250+ $25 to $150$25 to $150

E1, T1E1, T1

ReliabilityReliability

FiberFiberPhysical

obstructionsPhysical

obstructions

$250 to $1,000+$250 to $1,000+ $400 to $1000+$400 to $1000+ AvailabilityAvailability

$5,000 to $200,000+$5,000 to $200,000+ $0$0

MicrowaveMicrowave Licensing, Weather

Licensing, Weather

$15,000+$15,000+ $0$0

802.11802.11 $2,000 to $15,000

$2,000 to $15,000 $0$0 InterferenceInterference


Emerging Markets — Bridging


Monthly Leased Line OpEx

2 DS1: $600

1 DS3: $5000

TOTAL: $5600

RBOC provides guaranteed level of service via a Service Level Agreement (SLA)

RBOC

DS3DS1

DS1

New remote office

- No DS1 connection available

Traditional WAN Connectivity


Monthly Line Cost

2 DS1: $600

1 Fractional DS3: $3000

TOTAL: $3600

Wireless Installation Cost

7 350 Series Bridges Installed: $12,500 USD

Pay Back Period: 3 months

New building connected

Self managed

RBOC

22 Mbps

2 Mbps

2 Mbps

5 Mbps

802.11b Connectivity


Monthly Line Cost

2 DS1: $600

1 DS3: $5000

TOTAL: $5600

Wireless Installation Cost

7 1400 Series Bridges Installed: $40,000 USD

Pay Back Period: 8 months

New building connected

Self managed

RBOC

50 Mbps

14 Mbps

14 Mbps

27 Mbps

802.11a Connectivity


Role in Radio Network

Role in Radio Network • Determines

functionality within WLAN

• Determines which type of clients will be supported

File Server

BridgeBridge

Access PointAccess Point

PC CardPC CardPCI CardPCI Card

Workgroup Bridge

Workgroup Bridge

Bridge


Parent – Child Relationship (Root Bridge vs. Non-Root Bridge)


Root Mode: Access Point vs. Bridge


Root Bridge


Non-Root Bridge with Clients


Non-Root Bridge without Clients


Bridge Configured as a Root Access Point


Bridge Configured as a Repeater Access Point


Bridge Configured as a Site Survey Client


Distances Limited by 802.11 Specification


Connecting the 350 Bridge

ss


BR350—Front Cover LED’s


802.11b Bridge

Bridge Model Bridge Model

BR350BR350

Note: Distances over 25 miles or 40 Km are very hard to align and install!

Data Rate Data Rate

11 Mbps11 Mbps

11 Mbps11 Mbps

51.7 83.251.7 83.2

20.5 33.0 20.5 33.0

32.7 52.5 32.7 52.5

32.6 52.432.6 52.4

21 dBi Dish21 dBi Dish

41.0 66.041.0 66.02 Mbps2 Mbps

5.5 Mbps5.5 Mbps

Max. Distance

Miles Km

Max. Distance

Miles Km

Optional Antenna Optional Antenna

Standard Cable (6.7 dB/100 ft. loss)

(6.7 dB/30.5 m)

Standard Cable (6.7 dB/100 ft. loss)

(6.7 dB/30.5 m)

1 Mbps1 Mbps





50 ft (15.2m)/side50 ft (15.2m)/side

20 ft (6.1m)/side20 ft (6.1m)/side

50 ft (15.2m)/side50 ft (15.2m)/side

50 ft (15.2m)/side50 ft (15.2m)/side

50 ft (15.2m)/side50 ft (15.2m)/side


802.11b Common Questions

Cisco Aironet BridgeCisco Aironet Bridge How Fast?How Fast?

Max data rateMax data rate

20.5 Miles 33 Km20.5 Miles 33 Km

11 Mbps11 Mbps

5.5 Mbps5.5 Mbps

3.6 Miles 5.8 Km3.6 Miles 5.8 Km

How Far? How Far?

Typical throughputTypical throughput

Yagi antennaYagi antenna

2 Mbps2 Mbps

1.4 Mbps1.4 Mbps

7.3 miles 11.7 Km7.3 miles 11.7 Km

25+ miles 40+ Km25+ miles 40+ Km

Dish antennaDish antenna

Note: All distances may be limited by governing bodies and standards.


Optional 2.4GHz Antennas for Long Range

• 13.5 dBi YagiDistances over

7.3 miles @ 2 Mbps11.7 Km @ 2 Mbps3.6 miles @ 11 Mbps5.8 Km @ 11 Mbps

• 21 dBi Solid DishFor distances up to

25+ miles @ 2 Mbps40+ Km @ 2 Mbps 20.5 miles @ 11 Mbps33 Km @ 11 Mbps

Note: Distances include 50 feet of low loss cable and 10 dB fade margin


11b Bridge Application: School District

LincolnElementaryYagi

BodeElementaryYagi

RichardsonElementaryYagi

PriceElementaryYagi

Dewitt ElementaryYagi

BolichMiddle SchoolYagi

RobertsMiddle SchoolDish

Weaver-Special EducationDish

High School 2 BridgesOne 12 dBi omniOne Dish Administration

2 BridgesOne 12 dBi omniOne Yagi

U N I V E R S I T YU N I V E R S I T Y

Channel #11

Channel #6

Channel #1


Lightning


Lightning Arrestor

Designed to protect LAN devices from static electricity and lightning surges that travel on coax transmission lines

RP-TNC connectors used on all Cisco Antennas

To Antenna

Ground Wire

From RF Device

Lug

LockwasherNut


Direct Strike Protection


Coax Connection Sealing

Number one problems with bridges - water in the connectors

Proper sealing is important

Coax Seal is one product that is inexpensive and works great


Path Loss Considerations

The following are needed to determine coverage · Antenna Gain· Transmitter Power· Receiver Performance· Cable Losses· Environmental Structures


Calculations of Coverage Performance

Coax Length150 ft (45.7)?

Coax Length100 ft (30.5 m)?

Wants 11 Mbps data rateDistance = 13 miles (20.9 Km)

Towers needed to clear trees andother buildings


Bridge Range Calculation Utility


Bridge Distance Calculations (cont.)


Bridge Distance Calculations (cont.)


1400 Series Bridge


1400 Series

High Performance

•Up to 54Mbps throughput

•Outdoor Only

Flexible

•Point to point and point to multi-point bridging

•Multiple mounting and antenna options

Secure

•Enterprise-class security

Feature Rich

•Intelligent Network Services via IOS

AIR-BR1410A-A-K9 AIR-BR1410A-A-K9-N


1400 Modes

•Root

•Non-Root

•Install-Mode


Power Injector LR

Converts standard 10/100 baseT Ethernet RJ-45 interface to F-Type connector dual coaxial cable

Power provided over dual coaxial cable with power discovery to protect other appliances

Support for longer cable runs by resetting the 100 meter, 100baseT Ethernet timer, enabling total cable runs of 200 meters.

Surge protection provided at the F-Type connectors to protect infrastructure devices


802.11a Bridge

Bridge Model Bridge Model

14001400

Note: Distances over 25 miles or 40 Km are very hard to align and install!

Data Rate Data Rate

54 Mbps54 Mbps

9 Mbps9 Mbps

12 xx.0 12 xx.0

23 xx 23 xx

7.5 xx7.5 xx


9 xx 9 xx16 Mbps16 Mbps

54 Mbps54 Mbps

Max. Distance

Miles Km

Max. Distance

Miles Km

Optional Antenna Optional Antenna


22 dBi Int.22 dBi Int.

22 dBi Int.22 dBi Int.


Optional 5GHz Antennas for Long Range

Network configurations

•Point to point

•Point to multi-point

Roof, pole, and wall mounting options

5.8 GHz Unlicensed Band Operation

•Rapid deployment and re-commissioning

Operating temp range: -30 to +55 oC

Humidity: 0 to 100%

9 dBi omni (Vertical polarization)

9.5 dBi sector (H or V polarization)

28 dBi dish (H or V polarization)


Summary

• Identify characteristics of Cisco Aironet 802.11a products.

• Identify characteristics of Cisco Aironet 802.11b products.

454545© 2003, Cisco Systems, Inc. All rights reserved.

Documents

© 2003, Cisco Systems, Inc. All rights reserved. FWL 1.0—6-1 111 © 2003, Cisco Systems, Inc. All rights reserved