Cisco ASA Series Cli Configuration Manual page 275

Chapter 1 Configuring a Cluster of ASAs
We recommend using Individual interfaces for management, even if you use Spanned EtherChannels for
your data interfaces. Individual interfaces let you connect directly to each unit if necessary, while a
Spanned EtherChannel interface only allows remote connection to the current master unit.
Note
If you use Spanned EtherChannel interface mode, and configure the management interface as an
Individual interface, you cannot enable dynamic routing for the management interface. You must use a
static route.
For an Individual interface, the Main cluster IP address is a fixed address for the cluster that always
belongs to the current master unit. For each interface, you also configure a range of addresses so that
each unit, including the current master, can use a Local address from the range. The Main cluster IP
address provides consistent management access to an address; when a master unit changes, the Main
cluster IP address moves to the new master unit, so management of the cluster continues seamlessly. The
Local IP address is used for routing, and is also useful for troubleshooting.
For example, you can manage the cluster by connecting to the Main cluster IP address, which is always
attached to the current master unit. To manage an individual member, you can connect to the Local IP
address.
For outbound management traffic such as TFTP or syslog, each unit, including the master unit, uses the
Local IP address to connect to the server.
For a Spanned EtherChannel interface, you can only configure one IP address, and that IP address is
always attached to the master unit. You cannot connect directly to a slave unit using the EtherChannel
interface; we recommend configuring the management interface as an Individual interface so you can
connect to each unit. Note that you can use a device-local EtherChannel for management.
Master Unit Management Vs. Slave Unit Management
Aside from the bootstrap configuration, all management and monitoring can take place on the master
unit. From the master unit, you can check runtime statistics, resource usage, or other monitoring
information of all units. You can also issue a command to all units in the cluster, and replicate the console
messages from slave units to the master unit.
You can monitor slave units directly if desired. Although also available from the master unit, you can
perform file management on slave units (including backing up the configuration and updating images).
The following functions are not available from the master unit:
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RSA Key Replication
When you create an RSA key on the master unit, the key is replicated to all slave units. If you have an
SSH session to the Main cluster IP address, you will be disconnected if the master unit fails. The new
master unit uses the same key for SSH connections, so you do not need to update the cached SSH host
key when you reconnect to the new master unit.
ASDM Connection Certificate IP Address Mismatch
By default, a self-signed certificate is used for the ASDM connection based on the Local IP address. If
you connect to the Main cluster IP address using ASDM, then a warning message about a mismatched
IP address appears because the certificate uses the Local IP address, and not the Main cluster IP address.
Monitoring per-unit cluster-specific statistics.
Syslog monitoring per unit.
Information About ASA Clustering
Cisco ASA Series CLI Configuration Guide
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