High availability (HA)
in controllers allows you to reduce the downtime of the wireless networks that
occurs due to the failover of controllers.
(Active:Standby-Hot) stateful switchover of access points (AP SSO) is
supported. In an HA architecture, one controller is configured as the primary
controller and another controller as the secondary controller.
After you enable HA,
the primary and secondary controllers are rebooted. During the boot process,
the role of the primary controller is negotiated as active and the role of the
secondary controller as standby-hot. After a switchover, the secondary
controller becomes the active controller and the primary controller becomes the
standby-hot controller. After subsequent switchovers, the roles are
interchanged between the primary and the secondary controllers. The reason for
switchovers are either because of manual trigger, or a controller, or network
During an AP SSO, all
the AP sessions statefully switch over and all the clients are deauthenticated
and reassociated with the new active controller except for the locally switched
clients in the FlexConnect mode.
controller continuously monitors the health of the active controller through a
direct wired connection over a dedicated redundancy port. Both the controllers
share the same configurations, including the IP address of the management
Before you enable HA,
ensure that both the controllers are physically connected through the redundant
port using an Ethernet cable. Also, ensure that the uplink is connected to an
infrastructure switch and that the gateway is reachable from both the
In HA architecture,
the redundancy port and redundant management interfaces have been introduced.
ACL and NAT IP
configurations are synchronized to the HA standby controller when these
parameters are configured before HA pair-up. If the NAT IP is set on the
management interface, the access point sets the AP manager IP address as the
NAT IP address. This issue is seen only when the NAT IP address and ACL are set
on the management interface before you enable high availability.
The following are some
guidelines for high availability:
We recommend that
you do not pair two controllers of different hardware models. If they are
paired, the higher controller model becomes the active controller and the other
controller goes into maintenance mode.
We recommend that
you do not pair two controllers on different controller software releases. If
they are paired, the controller with the lower redundancy management address
becomes the active controller and the other controller goes into maintenance
All download file
types, such as image, configuration, web-authentication bundle, and signature
files– are downloaded on the active controller first and then pushed to the
should be downloaded separately on each controller before they are paired.
You can upload
file types such as configuration files, event logs, crash files, and so on,
from the standby-hot controller using the GUI or CLI of the active controller.
You can also specify a suffix to the filename to identify the uploaded file.
To perform a peer
upload, use the service port. In a management network, you can also use the
redundancy management interface (RMI) that is mapped to the redundancy port or
RMI VLAN, or both, where the RMI is the same as the management VLAN. Note that
the RMI and the redundancy port should be in two separate Layer2 VLANs, which
is a mandatory configuration.
If the controllers
cannot reach each other through the redundant port and the RMI, the primary
controller becomes active and the standby-hot controller goes into the
To achieve HA
between two Cisco Wireless Services Module 2 (WiSM2) platforms, the controllers
should be deployed on a single chassis, or on multiple chassis using a virtual
switching system (VSS) and extending a redundancy VLAN between the multiple
VLAN should be a nonroutable VLAN in which a Layer 3 interface should not be
created for the VLAN, and the interface should be allowed on the trunk port to
extend an HA setup between multiple chassis. Redundancy VLAN should be created
like any other data VLAN on Cisco IOS-based switching software. A redundancy
VLAN is connected to the redundant port on Cisco WiSM2 through the backplane.
It is not necessary to configure the IP address for the redundancy VLAN because
the IP address is automatically generated. Also, ensure that the redundancy
VLAN is not the same as the management VLAN.
When the RMIs
for two controllers that are a pair, and that are mapped to same VLAN and
connected to same Layer3 switch stop working, the standby controller is
" mobilityHaMac is out of range" xml message is seen during the active/standby
second switch over in HA setup. This occurs if mobility HA mac field is more
- When HA is enabled, the standby controller always uses the Remote Method
Invocation (RMI), and all the other interfaces, dynamic and management, are
The RMI is meant to be used only for active and standby
communications and not for any other purpose.
When HA is
enabled, ensure that you do not use the backed-up image. If this image is used,
the HA feature might not work as expected:
port and route information that is configured is lost after you enable SSO. You
must configure the service port and route information again after you enable
SSO. You can configure the service port and route information for the
standby-hot controller using the
WiSM2, service port reconfigurations are required after you enable redundancy.
Otherwise, Cisco WiSM2 might not be able to communicate with the supervisor. We
recommend that you enable DHCP on the service port before you enable
that you do not use the
on the standby-hot controller directly. If you use this, unsaved configurations
will be lost.
We recommend that
you enable link aggregation configuration on the controllers before you enable
the port channel in the infrastructure switches.
configurations that require reboot of the active controller results in the
reboot of the standby-hot controller.
The Ignore AP list
is not synchronized from the active controller to the standby-hot controller.
The list is relearned through SNMP messages from Cisco Prime Infrastructure
after the standby-hot controller becomes active.
- In Release 7.3.x, AP SSO is
supported, but client SSO is not supported, which means that after an HA setup
that uses Release 7.3.x encounters a switchover, all the clients associated
with the controller are deauthenticated and forced to reassociate.
- You must manually configure
the mobility MAC address on the then active controller post switchover, when a
peer controller has a controller software release that is prior to Release 7.2.
The active and
standby-hot controllers use the RMI to check the health of the peer controller
and the default gateway of the management interface through network
The RMI is also
used to send notifications from the active controller to the standby-hot
controller if a failure or manual reset occurs. The standby-hot controller uses
the RMI to communicate to the syslog, NTP/SNTP server, FTP, and TFTP server.
It is mandatory to
configure the IP addresses of the Redundancy Management Interface and the
Management Interface in the same subnet on both the primary and secondary
The redundancy port
is used for configuration, operational data synchronization, and role
negotiation between the primary and secondary controllers.
The redundancy port
checks for peer reachability by sending UDP keepalive messages every 100
milliseconds (default frequency) from the standby-hot controller to the active
controller. If a failure of the active controller occurs, the redundancy port
is used to notify the standby-hot controller.
If an NTP/SNTP
server is not configured, the redundancy port performs a time synchronization
from the active controller to the standby-hot controller.
In Cisco WiSM2, the
redundancy VLAN must be configured on the Cisco Catalyst 6000 Supervisor Engine
because there is no physical redundancy port available on Cisco WiSM2.
The redundancy port
and the redundancy VLAN in Cisco WiSM2 are assigned an automatically generated
IP address in which the last two octets are obtained from the last two octets
of the RMI. The first two octets are always 169.254. For example, if the IP
address of the RMI is 184.108.40.206, the IP address of the redundancy port is