L_8068 Wireless Networking Considerations

1
L_8068Wireless Networking Considerations

• Define wireless networking technologies and
  standards
• Describe Cisco Unified Wireless Network
  architecture
• Design wireless networks for efficiency, security
  and redundancy

2
Lesson 1WLAN Technologies and Standards

• Define WLAN standards
• Describe ISM and UNII radio frequencies
• Analyze WLAN security and authentication options

3
Wireless LAN

• Allow users to connect without cables
• Common areas
• Outdoors
• Warehouses
• Hotel guest access
• Public spaces such as coffee shops
• Residential

4
WLAN Standards

• IEEE 802.11-2007 is full current standard
• Legacy 802.11 (1997) 1-2 Mbps DSSS/FHSS
• 802.11b (1999) Wi-Fi 1-11 Mbps DSSS
• 802.11a (1999) Wi-Fi5 6-54 Mbps UNII
• 802.11g (2003) up to 54 Mbps ISM
• 802.11n (draft) up to 540 Mbps

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802.11 Overview
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ISM Frequencies

• ISM
• ITU-R radio specifications
• Regulated by FCC in U.S.
• 900 - 928 MHz
• 2.4 - 2.5 GHz
• 5.75 - 5.875 GHz

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ISM Channels
Frequency
2.402 GHz
2.483 GHz
2.441 GHz
22 MHz
1
6
11
2
7
3
8
9
4
10
5
8
UNII Frequencies

• UNII
• specified for 802.11a wireless
• 5.15 - 5.35 GHz (UNII 1)
• 5.47 - 5.725 GHz (UNII 2)
• 5.725 - 5.875 GHz (UNII 3 - overlaps with ISM)

9
WLAN Layer 2 Access and Device Identification

• 802.11 uses CSMA/CA at the MAC layer
• Stations listen for activity then transmit
• Use countdown timer
• SSID identifies WLAN devices
• 2 to 32 characters
• All devices in WLAN must share same ID

10
WLAN Security

• Unencrypted WLANs present security risk
• 802.11b uses WEP, which is not very secure
• 802.11i (2004) provides additional security
• 802.1X authentication w/EAP
• RSN keeps track of associations
• AES for confidentiality, integrity and origin
  authentication

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WLAN Authentication
LWAPP Tunnel
EAP/RADIUS Tunnel
WLC
LWAP
Authentication Server
Enterprise Infrastructure
Wireless Client
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Authentication Options

• EAP-TLS IETF open standard
• PEAP Cisco, Microsoft, RSA Security
• EAP-TTLS Funk Software, Certicom
• LEAP - Cisco proprietary
• EAP-FAST Cisco proposed enhanced alternative to
  LEAP

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Lesson 2Cisco Unified Wireless Network

• Identify elements of the Cisco UWN architecture
• Describe the components and functions of WLAN
  controllers
• List Cisco wireless device types
• Discuss roaming and mobility groups

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Cisco UWN Architecture

• Five network elements
• Client devices
• Access points (AP)
• Network unification (controllers)
• Network management
• Mobility services

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UWN Architecture
Network Management Mobility Services
Unified Network
Outdoor Mesh APs
Controllers
Access Points
Clients
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LWAPP

• Draft IETF standard for communication between APs
  and controllers
• Cisco implements split-MAC operation
• LWAP MAC functions
• Controller MAC functions

• 802.11e
• 802.11i

• 802.11
• 802.11 control

• 802.11 MAC management
• 802.11 resource reservation

• 802.11i

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LWAPP Tunnels
WLC
Wired Network
L3 LWAPP Tunnels
Wireless Clients
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LWAPP AP Modes

• Local mode
• Remote Edge AP (REAP) mode
• Monitor mode
• Rogue detector mode
• Sniffer mode
• Bridge mode

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LWAPP Discovery

• LWAPs perform DHCP discovery to obtain IP address
• Layer 3 LWAPP discovery follows
• If WLC does not respond, AP reboots and repeats
  the request

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WLAN Controller Components
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WLC Interface Types

• Management interface
• Service-port interface
• AP Manager interface
• Dynamic interface
• Virtual interface

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WLC Scalable WLCs
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Indoor APs

• Aironet 1250 802.11n draft certified
• Aironet 1240AG 802.11a/b/g
• Aironet 1130AG 802.11a/b/g
• Cisco 880 series ISR

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Outdoor APs

• Aironet 1500 outdoor mesh
• Aironet 1520 outdoor mesh a/b/g coax
• Aironet 1300 outdoor AP/bridge
• Aironet 1400 high performance outdoor bridge

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Cisco WCS

• Web-based SNMP management tool

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Roaming

• Intracontroller
• Different AP in same WLC
• Layer 2 Intercontroller
• Different WLC, same IP subnet
• Layer 3 Intercontroller
• Different WLC, different IP subnet

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Mobility Groups

• For Intercontroller roaming to occur, all WLCs
  must be in the same mobility group
• Can be up to 24 controllers
• Minimize Layer 3 roaming
• Recommended lt 10 ms rt latency between controllers

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Guest Services

• Two ways to segregate traffic
• Use separate VLANs for corporate and guest access
• Only guest SSID is broadcast
• Use EoIP to tunnel guest traffic to and anchor
  WLC
• Logically segments traffic

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Wireless Design Basics

• Identify WLAN design steps
• Discuss radio management
• Design the campus, branch and outdoor mesh

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Design Considerations

• Number of APs
• Consider number of users per AP
• Placement of APs
• Centralized location, conference rooms
• Power supply for APs
• PoE preferred
• Number of WLCs
• Number of APs, redundancy requirements
• Placement of WLCs
• Wiring closet, data center, redundancy

31
Radio Management

• Cisco RRM (Radio Resource Management)
• Radio resource monitoring
• Dynamic channel assignment
• Interference detection and avoidance
• Dynamic transit power control
• Coverage hole detection and correction
• Client and network load balancing

32
RF Groups

• Clustered WLCs coordinate RRM
• Can be scaled to multiple floors, buildings or
  entire campus
• APs communicate with neighbors
• Multiple WLCs elect group leader

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RF Site Surveys

• Define customer requirements
• Service levels, VoIP, etc
• Identify coverage areas and density
• Peak use times, conference rooms
• Determine AP locations
• Power, network access, mounting location
• Perform a live survey using an AP
• Discover sources of interference
• Document findings
• Target locations, signal readings, throughput

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Controller Redundancy

• Dynamic
• APs use LWAPP to load balance across WLCs
• Longer failover times, unpredictable
• Deterministic
• Recommended best practice
• N1, NN, NN1

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N1 Redundancy
Primary WLC for AP1 and AP2
AP1
AP2
Secondary WLC
AP3
Primary WLC for AP3 and AP4
AP4
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NN Redundancy
Primary WLC for AP1 and AP2 Secondary WLC for AP3
and AP4
AP1
AP2
AP3
Primary WLC for AP3 and AP4 Secondary WLC for AP1
and AP2
AP4
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NN1 Redundancy
Primary WLC for AP1 and AP2 Secondary WLC for AP3
and AP4
AP1
AP2
Tertiary WLC
AP3
Primary WLC for AP3 and AP4 Secondary WLC for AP1
and AP2
AP4
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Branch Design

• REAP allows remote LWAPs to connect to central
  WLC via WAN
• H-REAP provides additional security
• Round-trip delay should not exceed 100ms
• Local MAC allows local resource access without
  going back to WLC

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Outdoor Wireless Mesh

• Eliminates need to wire each AP
• Allows seamless roaming
• Components are as follows
• WCS SNMP management interface
• WLC links to wired network
• RAP Rooftop AP - mesh gateway
• MAP Mesh access points communicate with RAP

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Mesh Design Considerations

• No more than 20 MAP nodes per RAP
• Supports up to 32
• Four or fewer hops recommended
• Supports up to 8
• One hop for indoor deployment
• Latency is 2-3 ms per hop