Техническая Инструкция для Cisco Cisco 2000 Series Wireless LAN Controller
These rules are best described with some examples:
The AP is new, out of the box, and never joined to a controller. Does this AP load balance across 3
controllers in a mobility group?
controllers in a mobility group?
No. The AP must discover all 3 controller management IP addresses during boot via OTAP, DNS
(with all 3 management ip addresses defined), 255.255.255.255, and DHCP Option 43 (with all 3
management ip addresses included) for load balancing. The AP sends a discovery request to all
known controllers and joins the controller with the most excess AP capacity. If only 1 controller is
defined in DHCP option 43/DNS, the new APs always join that controller.
(with all 3 management ip addresses defined), 255.255.255.255, and DHCP Option 43 (with all 3
management ip addresses included) for load balancing. The AP sends a discovery request to all
known controllers and joins the controller with the most excess AP capacity. If only 1 controller is
defined in DHCP option 43/DNS, the new APs always join that controller.
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If there is 1 controller defined in DHCP option 43/DNS and there are 3 controllers in the mobility
group, does it load balance across the 3 controllers in a mobility group if you reboot the AP after it
joins the controller in DHCP option 43?
group, does it load balance across the 3 controllers in a mobility group if you reboot the AP after it
joins the controller in DHCP option 43?
No. If the AP reboots or is reset, it always joins the controller in the DHCP option 43/DNS or the last
joined controller. However, if the AP loses the heartbeat to the current controller, it does not reboot.
Instead, the AP goes directly into discovery mode. Because it did not reboot, the AP still has the
mobility members and sends each controller in the mobility group a discovery request.
joined controller. However, if the AP loses the heartbeat to the current controller, it does not reboot.
Instead, the AP goes directly into discovery mode. Because it did not reboot, the AP still has the
mobility members and sends each controller in the mobility group a discovery request.
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What does the AP use mobility members for?
AP fallback (unconfigured controller to configured controller [primary/secondary/tertiary]) and
learning other controller IP addresses after it joins a controller in case it loses contact with the current
controller. Remember that the AP forgets the mobility members across reboots.
learning other controller IP addresses after it joins a controller in case it loses contact with the current
controller. Remember that the AP forgets the mobility members across reboots.
Note: There can be a race condition on this algorithm. Between the time the controller replies to the
discovery request of the AP and the time the AP sends in a join request to the AP−manager, the
number of APs joined to the AP−manager might have changed if there is a large number of APs that
join the controller simultaneously. For example, if there is a power outage and the power on the APs
comes back simultaneously, the APs might not load balance evenly across the controllers.
discovery request of the AP and the time the AP sends in a join request to the AP−manager, the
number of APs joined to the AP−manager might have changed if there is a large number of APs that
join the controller simultaneously. For example, if there is a power outage and the power on the APs
comes back simultaneously, the APs might not load balance evenly across the controllers.
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AP Fallback
Unlike Hot Standby Router Protocol (HSRP) standby, AP fallback disrupts wireless service while the AP
failsover and then falls back to the configured controller. Remember that once an AP joins a controller, the AP
is only programmed to leave that controller if:
failsover and then falls back to the configured controller. Remember that once an AP joins a controller, the AP
is only programmed to leave that controller if:
The AP loses responses from its keepalives to the controller.
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The customer resets the AP via the controller.
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The AP receives notification, via the mobility group members update from the current controller, that
a configured controller (Primary/Secondary/Tertiary) is up, and the AP is currently joined to an
unconfigured controller with AP fallback enabled.
a configured controller (Primary/Secondary/Tertiary) is up, and the AP is currently joined to an
unconfigured controller with AP fallback enabled.
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It is important to note that the AP only performs AP fallback from an unconfigured controller to a configured
controller (Primary/Secondary/Tertiary). The AP does not fall back from a secondary controller to the primary
controller if it is currently joined to the secondary controller. This is because the secondary controller is a
configured controller.
controller (Primary/Secondary/Tertiary). The AP does not fall back from a secondary controller to the primary
controller if it is currently joined to the secondary controller. This is because the secondary controller is a
configured controller.
When the AP is joined to an unconfigured controller and it is notified that a configured controller is up and
available via the mobility group members, it immediately leaves the current controller and joins the
configured controller.
available via the mobility group members, it immediately leaves the current controller and joins the
configured controller.
Note: The behavior explained in this section about AP fallback is applicable to controllers that run version
3.2.171.5 or earlier. Later versions of controller firmware do not have these problems. In the latest version of
3.2.171.5 or earlier. Later versions of controller firmware do not have these problems. In the latest version of