Term
| What is the max round-trip propagation delay in a collision domain in regards to the design rules for Ethernet? |
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Definition
512-bit times
So, on a 10mbps ethernet, the max round trip delay is 51.s microseconds (512 * .1)
For 100mbps, its only 5.12 (512 * .01) |
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Term
1. What is the maximum diameter for 100mbps ethernet? 10mbps?
2. What is the limit for repeaters with 100mbps? |
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Definition
1. 205 meters. 10baseT=500m 10base5=2500m
2. 2 repeaters |
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Term
| What are the specifications for 1000base-LX long wavelength ethernet? |
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Definition
- uses long wave
- uses multimode or single-mode fiber
- Max length of multimode fiber:
- 62.5 micrometer fiber = 440m
- 50 micrometer fiber = 550m
- Max length for single mode fiber (9 micrometers) is 5km
- Uses 8B10B encoding with simple NRZ |
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Term
| What are the specifications for 1000base-SX gigabit ethernet? |
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Definition
- Used short wave
- Used on multimode fiber only
- Max length:
- 62.5 micrometers - 260m
- 50 micrometers - 550m
- Uses 8B10B encoding with simple NRZ |
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Term
| What are the specifications for 1000base-CX gigabit ethernet over coaxial cable? |
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Definition
- Uses a short run copper
- Runs over a pair of 150 ohm balanced coaxial cable (twinax)
- Max length is 25m
- Mainly for server connections
- Uses 8B10B encoding with simple NRZ |
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Term
| What are the specifications for 1000base -T gigabit ethernet of UTP? |
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Definition
- Cat5, 4-pair UTP
- Max length = 100m
- encoding defined is a 5 level coding scheme
- 1 byte is sent over the 4 pairs at 125 MHz |
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Term
| What is the 5-4-3 rule in regards to using repeaters? |
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Definition
5 - Maximum path between 2 stations on a network
4 - Repeaters between those segments
3 - Max populated segments |
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Term
| Where is the preferred location for marking traffic? |
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Definition
| As close to the source as possible |
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Term
| Describe the use of Cisco group management protocol (CGMP) |
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Definition
| Its a Cisco-proprietary protocol implements to control multicast traffic at layer 2. The LAN switch can speak with the IGMP router to find out the MAC addresses of the hosts that want to receive the multicast packets. |
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Term
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Definition
| Switches listen to IGMP messages between the hosts and routers. If a host sends an IGMP query message to the router, the switch adds the host to the multicast group and permits that port to receive multicast traffic. the port is removed from the multicast traffic if an IGMP leave message is sent from the host to the router. |
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Term
| Describe the different application types in a LAN design. |
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Definition
- Peer-to-peer - IM, file sharing , IP phone calls, and video conferencing.
- Client-local server - servers located in the same segment or close by.
- Client/server farm - mail, file, and db servers. Access is reliable and controlled.
- Client/enterprise edge servers - external services such as SMTP, web, public servers, and e-commerce. |
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Term
| What are 2 basic approaches in regards to WLAN security design? |
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Definition
- Use lightweight extensible authentication protocol (LEAP) to secure authentication
- Use of VPN with IP security (IPsec) to secure traffic from the WLAN to the wired network. |
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Term
| What are the 5 elements of the Cisco unified wireless network (UWN) architecture? |
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Definition
- Client devices - laptops, workstations, IP phones, and PDAs
- Access points - devices that provide access to the wireless network
- Network unification - The WLAN should be able to support wireless applications by providing security policies, QoS, intrusion prevention, and radio frequency (RF) management.
- Network management - The Cisco wireless control system (WCS) provides a central management tool that lets you design, control, and monitor wireless networks.
- Mobility services - guess access and location and voice services. |
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Term
| What are some of the benefits of Cisco's UWN? |
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Definition
- Reduce TCO
- Enhanced visibility control
- Dynamic RF management
- WLAN security
- Unified wired and wireless network
- Enterprise mobility
- Enhanced productivity and collaboration |
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Term
| What is lightweight access point protocol (LWAPP) |
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Definition
| LWAPP is a draft IETF standard for control messaging for setup, authentication, and operations between access points (AP) and the wireless LAN controllers (WLC) |
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Term
| How does Cisco's UWN split-MAC operation work? |
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Definition
| LWAPs communicate with the WLC, using control messages over the wires network. LWAPP data messages are encapsulated and forwarded to and from the wireless clients. |
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Term
| What is the difference between layer 2 tunneling and layer 3 tunneling in regards to LWAPP? |
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Definition
| With layer 2, control messages between AP and WLC did not require an IP address on the AP, so the WLC needed to be on every subnet on which the AP resides, making layer 3 the preferred solution. |
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Term
| Messages from the WLC use what ports? |
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Definition
| UDP port 12223 for control and UDP port 12222 for data messages. |
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Term
| What are the 6 different modes that an LWAPP access point operate? |
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Definition
- Local mode - default mode of operation. Every 60 seconds/180 seconds, the AP preforms noise floor measurements, measures interference, and scans for IDS events.
- Remote edge AP (REAP) mode - enables an LWAP to reside across a WAN link
- Monitor mode - allows specified LWAPP-enabled APs to act as dedicated sensors for location-based services, rogue AP detection, and IDS, instead of handling data traffic.
- Rogue detector mode - LWAPs that monitor rogue APs
- Sniffer mode - An LWAPP that functions as a sniffer and captures and forwards all the packets on a particular channel to a remote machine that runs airopeak
- Bridge mode - provides wireless bridging connectivity |
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Term
| Describe the layer 3 LWAPP discovery process |
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Definition
1. the AP sends a layer 3 LWAPP discovery request
2. All WLCs that receive the discovery request reply with a unicast LWAPP discovery response message.
3. The AP compiles a list of WLCs
4. The AP selects a WLC based on certain criteria
5. The AP validated the selected WLC and sends an LWAPP join response. An encryption key is selected and future message are encrypted. |
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Term
| How does a LWAP choose a WLC during the discovery process? |
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Definition
- Previously configures primary, secondary, and/or tertiary WLCs
- The WLC configured as the master controller
- The WLC with the most capacity for AP associations |
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Term
| With wireless clients, what are the different authentication options? |
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Definition
- EAP-transport layer security (EAP-TLS)
- Protected extensible authentication protocol (PEAP)
- EAP-tunneled TLS (EAP-TTLS)
- Cisco lightweight extensible authentication protocol (LEAP)
- EAP-flexible authentication via secure tunneling (EAP-FAST) |
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Term
| What are the 3 major components of WLCs? |
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Definition
- Wireless LANs (SSID)
- Interfaces
- Ports |
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Term
| What are the 5 different interface types on a WLC? |
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Definition
- Management interface - used for in-band management, connectivity to AAA, and layer 2 discover and association
- Service-port interface - used for out-of-band management
- AP manage interface - used for layer 3 discover and association. Has the source IP of the AP that is statically configured.
- Dynamic interface - analogous to VLANs and is designed for WLAN client data.
- Virtual interface - used for layer 3 security authentication, DHCP rely support, and mobility management |
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Term
What are the number of supported APs for each platform:
1. Cisco 2000 serices WLC
2. Cisco WLC for ISRs
3. Catalyst 3750 integrated WLC
4. Cisco 4400 series WLC
5. Cisco 6500 series WLC |
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Definition
1. Cisco 2000 serices WLC - 6
2. Cisco WLC for ISRs - 6
3. Catalyst 3750 integrated WLC - 50
4. Cisco 4400 series WLC - 100
5. Cisco 6500 series WLC - 300 |
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Term
| Describe the process of intracontroller roaming |
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Definition
| Intracontroller roaming occurs when the client moves association from one AP to another AP that is joined to the same WLC. The WLC updates the client DB with the new associated AP and does not change the client's IP. The client remains on the same WLC |
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Term
| Describe the process for layer 2 intercontroller roaming |
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Definition
| Intercontroller roaming occurs when a client moves association from one AP to another AP that is joined to a different WLC. Layer 2 roaming occurs when the client traffic is bridged to the same IP subnet. Traffic remains on the same IP subnet and no IP changes to the client occur. The client DB is moved from WLC1 to WLC2. |
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Term
| Describe the process of layer 3 intercontroller roaming |
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Definition
| This is when a client moves association from one AP to another AP that is joined to a different WLC. Then the traffic is bridged onto a different IP subnet. WLC2 exchanges mobility messages with WLC1. WLC1 marks the client with an "anchor" entry in its DB. The DB entry is copied over to WLC2's DB and marked as a "foreign" entry. The wireless client maintains its original IP and is re authenticated. |
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Term
| Explain how client traffic is routed when using layer 3 intercontroller roaming |
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Definition
| Traffic from the client is forwarded by the foreign WLC. But the traffic to the client arrives at the anchor WLC, which forwards it through an ethernet-in-IP (etherIP) tunnel to the foreign WLC. The foreign WLC forwards the data traffic to the client. |
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Term
| How do WLCs work when assigned to a mobility group? |
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Definition
| The WLCs dynamically exchange mobility messages and tunnel data via etherIP. Mobility groups support up to 24 controllers. The WLCs exchange messages using UDP port 16666 for unencrypted messages or UDP port 16667 for encrypted messages. |
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Term
| What is Cisco's recommended latency between WLCs? |
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Definition
| 10 ms of round-trip time latency |
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Term
| Between layer 2 and layer 3 intercontroller roaming, which does Cisco find more efficient? |
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Definition
| Layer 2 roaming because of the asymmetric communication of layer 3 roaming. |
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Term
| What are the 2 different types of controller redundancy designs? |
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Definition
- Deterministic design - The AP is configured with a primary, secondary, and tertiary controller. It requires more upfront planning but has a faster failover time. Also the recommended best practice.
- Dynamic design - uses LWAPP to load balance APs across WLCs. LWAPP populates APs with a backup WLC. This solution works better when WLCs are in a centralized cluster. Solution is easier to deploy and allows APs to load balance, but with longer failover times ad unpredictable operation. |
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Term
| Explain a N+1 WLC redundancy design |
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Definition
| A single WLC acts as a backup of multiple WLCs. One design constraint is that the backup WLC may become oversubscribed if there are too many failures of the primary controllers. |
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Term
| Explain an N+N WLC redundancy design |
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Definition
| An equal number of controllers back up each other. So WLC1 is a backup for WLC2, and vise-versa. |
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Term
| Explain a N+N+1 WLC redundancy design |
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Definition
| An equal number of controllers back up each other plus a backup WLC configured as the tertiary WLC for the APs. |
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Term
| What are the recommended best practices for APs? |
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Definition
- No more than 20 data devices per AP
- No more than 7 voice over WLAN (VoWLAN) calls using G.711 or 8 VoWLAN calls over G.729 |
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Term
| What is Cisco Radio Resource Management(RRM)? |
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Definition
| Its a method to manage AP radio frequency channels and power configuration. Cisco WLCs use RRM algorithm to automatically configure, optimize, and self-heal. |
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Term
| Describe Cisco's RRM functions |
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Definition
- Radio resource monitoring - Cisco LWAPs monitor all channels. Collected packets are sent to the WLC, which can detect rogue APs, clients and interfering APs
- Dynamic channel assignment - WLCs automatically assign channels to avoid interference
- Interference and avoidance
- Dynamic transmit power control - WLCs automatically adjust power levels
- Coverage hole detection and correction - WLCs may adjust the power output of APs if clients report that a low received signal strength indication level is detected (RSSI).
Client and network load balancing - Clients can be influenced to associate with certain APs to maintain network balance. |
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Term
| What are radio frequency groups? |
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Definition
| An RF group is a cluster of WLC devices that coordinate their RRM calculations. The WLC elect a group leader to analyze the RF data. The RF group leader exchanges messages with the RF group members using UDP port 12114 for 802.11b/g and UDP port 12115 for 802.11a |
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Term
| What are the steps involved when preforming an RF site survey? |
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Definition
Step 1 - Define customer requirements, such as service levels and support for VoIP
Step 2 - Identify coverage areas and user density, including peak use times, and conference room locations.
Step 3 - Determine preliminary Ap locations, which need power, wired network access, mounting locations, and antennas.
Step 4 - Preform the actual survey by using a AP to survey the location and received RF strength based on targeted AP placement.
Step 5 - document the findings by recording the target AP locations, data rates, and signal readings. |
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Term
| How are Ethernet of IP (EoIP) tunnels used for guest services? |
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Definition
| EoIP is used to logically segment and transport guest traffic from the edge AP to the anchor WLC. |
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Term
| What is Cisco's wireless mesh networking solution? |
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Definition
| It eliminates the need to wire each AP to the network and allows users to roam from one area to another without having to reconnect. |
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Term
| What are all the wireless mesh components? |
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Definition
- Wireless control system (WCS) is the wireless mesh SNMP management system that allows network-wide configuration and management.
- Wireless LAN controllers (WLC) link the mesh APs to the wired networks.
- Rooftop APs (RAP) connects the mesh to the wired network and servers as the root (or gateway). Also communicates with e MAPS.
- Mesh access points (MAPs) are remote APs. They communicate with the RAP to connect to the wired network |
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Term
| What are some mesh design recommendations? |
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Definition
- There is a 2-3 ms typical latency per hop
- For outdoor deployment, 4 or fewer hops are recommended for best performance. Max of 8 hops is supported.
- For indoor deployment, one hop is supported.
- 20 MAP nodes per RAP are recommended for best performance. Up to 32 MAPS are supported |
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Term
| What is the purpose of LWAPP with support of local MAC? |
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Definition
| Local MAC terminates the client traffic at the wired port of the AP versus at the WLC, providing MAC management support for association requests and actions. This allows direct local access to branch resources without requiring that data to travel to the WLC. This allows the wireless client to function even if a WAN link failure occurs. |
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Term
| What was REAP designed to support? |
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Definition
| REAP is designed to support remote offices by extending LWAPP control timers. Its the referred solution for LWAPs to connect to the WLC over a WAN. REAP devices support only layer 2 security policies, don't support NAT, and require a routable IP. |
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Term
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Definition
| H-REAP is an enhancement to REAP that provides additional capabilities such as NAT, more security options, and the ability to control up to 3 APs remotely. H-REAP is more delay-sensitive than REAP. The RTT must not exceed 100ms between the AP and the WLC |
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Term
What are the UDP ports used by the following WLAN protocols:
1. LWAPP control
2. LWAPP data
3. WLC exchange messages (unencrypted)
4. WLC exchange messages (encrypted)
5. RF group IEEE 802.11b/g
6. RF group IEEE 802.11a |
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Definition
1. 12223
2. 12222
3. 16666
4. 16667
5. 12114
6. 12115 |
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Term
| What are 2 methods for mark frames to provide CoS? |
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Definition
| Inter-Switch Link (ISL) and IEEE 802.1p/802.1Q |
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Term
| What standard does IEEE 802.11i use for confidentiality, integrity, and authentication? |
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Definition
| Advanced Encryption Standard (AES) |
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Term
| What are the 3 non-overlapping channels of IEEE 802.11b/g? |
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Definition
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Term
| What words can be used to correlate the feature sets of IOS versions and the features they provide? |
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Definition
- Advanced - Firewall, IDS, and VPN
- Enterprise - Appletalk, IPX, and IBM
- Services - ATM and MPLS (also supports VoIP and VoFR, with IP Voice) |
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