User guide

17-22 E
XTREME
W
ARE
S
OFTWARE
U
SER
G
UIDE
S
ERVER
L
OAD
B
ALANCING
(SLB)
enable slb vip ftpc service-check
config slb vip ftpc service-check ftp user test password testpass
Finally, enable SLB and configure the VLANs to be either client or server, using the
following commands.
enable slb
config vlan outside slb-type client
config vlan servers slb-type server
H
EALTH
C
HECKING
Three types of internal health checks are available:
• Ping-check
• Port-check
• Service-check
If any of the health checks enabled on a given node do not pass within the timeout
specified, the node is considered down. When a node is down, no new connections will
be established to that node until the node passes all configured health checks. If a
health check fails and if the svcdown-reset parameter has been enabled on an associated
VIP, existing connections for the VIP on this node will be closed by sending TCP Reset
to the client and node.
In the command-line interface, the
show
commands for the pool and vip show
individual node resources as up or down. New connections are only allowed if the VIP
and node in question are both enabled and up. A node is assumed to be up unless
health check is enabled and fails, in which case the node is marked down. A resource is
also marked down if it has been disabled and the number of existing connections drops
to zero. If a node is marked down for this reason, ping-checks and port-checks on this
node are automatically stopped to conserve system resources, but resume if the node is
enabled by the user.
The switch also supports external health checking. External health checking uses an
external service configured by the user to perform health checks and uses SNMP as a
mechanism to notify the switch of a server failure.