Wireless Infrastructure Flashcards
What is an autonomous AP
An AP that is self contained offering a fully functional BSS, it is a natural extension of the wired network. VLANs must be trunked between switch and AP.
How does the traffic flow between 2 clients on a autonomous AP
Client 1 > AP > Client 2
What is the drawbacks to autonomous AP’s
In large scale environments it can take a lot of time to configure all the VLANs on different AP’s.
SPT can cause issues with VLANs on different APs
What is a lightweight AP
Is a Cisco AP device that requires a wireless LAN controller to become fully functional.
What are CAPWAP tunnels
The AP and WLC are connected by a logical pair of CAPWAP tunnels. One for control device management and one for data.
What are the different modes of operation for a cisco AP
Local
FlexConnect
Monitor
Sniffer
Rouge detector
Bridge
Flex+bridge
SE-Connect
What is the default mode of operation for Cisco APs
Local - offers one or more BSS on a channel
What is FlexConnect
When the CAPWAP tunnel is split so the control tunnel to the WLC is split from the data tunnel.
If the WAN link goes down then the traffic can still forward.
What is the difference between a cisco AP in monitor mode and sniffer mode
Monitor - receives only, acts as a dedicated sensor.
Sniffer - acts as a packet capturing device to forward to a PC running wireshark
How does a rouge detector find rouge devcies
devices MAC addresses that appear on wired and wireless network.
What is bridge mode
used for point to point connections / P2MP
What are the different methods of deploying cisco wireless
Centralised
Public Cloud
Private Cloud
Distributed
Controller-less
What are the features of centralised wireless deployment
placed in a central location in the core
Makes it easier to enforce wireless security polices for all wireless clients
switch ports are access ports to the AP the wireless LAN traffic will be encapsulated within the CAPWAP tunnel to the WLC.
What is a public cloud deployment and what modes can you run the AP in
When the WLC is in a cloud outside of your network (possibly the internet) APs need to be run in FlexConnect or local.
Best practise is FlexConnect in the event the WAN link goes down.
Where is the WLC on a private cloud deployment
In the enterprise network
What is distributed wireless deployment
When the sites are remote so there is multiple WLCs in the network each deployed at the remote site.
What is controller less deployment
When a AP device has a built in WLC.
The CAPWAP tunnel is built between the AP with the embedded Controller and the other APs
A switch is capable of being a AP with an embedded controller
True or False
True
What is the process for a lightweight cisco AP joining a WLC
- Boot - boots from a small IOS image, requires a IP to communicate on the network.
- WLC discovery - AP will build a list of live WLCs.
- Build CAPWAP tunnel - attempts to build one or more CAPWAP tunnels and authenticate
- WLC join - CAPWAP join message to the WLC and receives the same from the WLC.
- Download image - the AP downloads the IOS image from the WLC if the versions don’t match. if they do no download needed.
- Download config - AP downloads configuration parameters from the WLC. (RF, security, QoS & SSID)
- Run state - BSS is provided to clients
- Reset - CAPWAP tunnels are torn down and process starts again.
What is the process for the AP discovering a list of live WLCs
- AP sends a CAPWAP broadcast message to the subnet.
- AP can be primmed (p,s or t)
- DHCP provides IP with an option 43 for a lsit of WLCs
- AP attempts to DNS resolve CISCO-CAPWAP-CONTROLLER
- AP resets itself and process starts again.
What is the process for an AP joining a WLC from the live list that the AP has discovered
- attempts to join the primmed WLCs
- Attempts to join the master WLC if one has been configured.
- Attempts to join the WLC with the lowest load to load balance the clients.
Why might a WLC reject a AP
Lack of licensing due to been oversubscribed.
What is a keepalive
It is a method of checking the WLC is still live. default interval is 30 seconds.
if no answer then 4 keepalives are sent at 3 second intervals. If no answer AP attempts to find another WLC.
WLCs support HA and SSO in an active/standby role
True or False
True
What is tags and polices in a wireless configuration and what are the types
Allows a set of parameters to be configured on a group of APs.
three types of tags are:
Site tag
policy tag
RF tag
What is client density
The amount of clients per AP.
Typically low client density = hight client performance due to less competition for air time.
What is a radiation pattern
Shows in a graphical format the relative signal strength around an antenna.
The graph has the H-plane and the E-plane.
The values on a radiation pattern (0, -5, -10, -15dB) are absolute dB values.
True or False
False - they are values relative to the maximum signal strength.
What is gain on an antenna
How effectively the antenna can focus the RF energy in a certain direction.
0dB - no gain sphere shape
+4dB - low gain omnidirectional shape
+12+ - high gain, very focused in one direction.
What is beam wdith
The measurement in degrees of the focused RF energy.
90 degrees would be not as focused as 20 degrees.
What is polarisation
In which plane (E or H) the fields of the wireless signal wave are changing.
for best results polarisation must match at transmitter and receiver.
What is the default polarisation for cisco devices
Vertical
What is an omnidirectional antenna
An antenna that propagates the signal in an equal direction.
Doughnut shaped pattern on the radiation pattern.
Low gain
What is a Dipole antenna
antenna has 2 wires that radiate the frequency.
Omnidirectional antenna
What is the integrated antenna
The antenna is within the AP, it is omnidirectional antenna.
What is a directional antenna
an antenna with higher gain so the RF signal is focused in one direction.
What is a patch antenna
directional antenna that has a broad egg shaped signal pattern.
What is a Yagi antenna
Directional antenna that has a more focused egg shaped signal pattern.
What is a dish antenna
an antenna where the wireless RF signal must be propagated over long distances.
A parabolic dish focuses the RF energy along one narrow elliptical pattern due to the target only being one receiver.
Very high gain.
