Cisco Cisco 2112 Wireless LAN Controller Folheto
AP logical collocation, and thus controller RF Grouping, is determined by APs receiving other APs’ Neighbor
Messages. These messages include information about the transmitting AP and its WLC (along with additional
information detailed in
Messages. These messages include information about the transmitting AP and its WLC (along with additional
information detailed in
Table 1
) and are authenticated by a hash.
When an AP receives a Neighbor Message (transmitted every 60 seconds, on all serviced channels, at
maximum power, and at the lowest supported data rate), it sends the frame up to its WLC to determine
whether the AP is a part of the same RF Group by verifying the embedded hash. An AP that either sends
undecipherable Neighbor Messages (indicating a foreign RF Group Name is being used) or sends no Neighbor
Messages at all, is determined to be a rogue AP.
maximum power, and at the lowest supported data rate), it sends the frame up to its WLC to determine
whether the AP is a part of the same RF Group by verifying the embedded hash. An AP that either sends
undecipherable Neighbor Messages (indicating a foreign RF Group Name is being used) or sends no Neighbor
Messages at all, is determined to be a rogue AP.
Figure 2: Neighbor Messages are sent every 60 seconds to the multicast address of 01:0B:85:00:00:00.
Given all controllers share the same RF Group Name, in order for an RF Group to form, a WLC need only
have a single AP hear one AP from another WLC (see Figures 3 through 8 for further details).
have a single AP hear one AP from another WLC (see Figures 3 through 8 for further details).
Figure 3: APs send and receive Neighbor Messages which are then forwarded to their controller(s) to
form RF Group.
form RF Group.
Neighbor Messages are used by receiving APs and their WLCs to determine how to create inter-WLC RF
Groups, as well as to create logical RF sub-Groups which consist of only those APs who can hear each other’s
Groups, as well as to create logical RF sub-Groups which consist of only those APs who can hear each other’s
Table 2: Neighbor Messages contain a handful of information
elements that give receiving controllers an understanding of
the transmitting APs and the controllers to which they are
connected.
elements that give receiving controllers an understanding of
the transmitting APs and the controllers to which they are
connected.
Field Name
Description
Radio Identifier
APs with multiple radios use this to identify
which radio is being used to transmit Neighbor
Messages
which radio is being used to transmit Neighbor
Messages
Group ID
A Counter and MAC Address of the WLC
WLC IP
Address
Address
Management IP Address of the RF Group
Leader
Leader
AP’s Channel
Native channel on which the AP services
clients
clients
Neighbor
Message
Channel
Message
Channel
Channel on which the neighbor packet is
transmitted
transmitted
Power
Not currently used
Antenna Pattern Not currently used