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4.1.4 Active Flows
Active flow capacity:
Specify the maximum number of active flow tracking resources that can be allocated from the choices
presented in the pull-down. If set to 'Auto-Tune', the FX will automatically set the active flow capacity
based upon the hardware platform and other criteria. An 'Active Flow' is a connection (either UDP or
TCP) between a client and server which flows through the FX. If no data flows through the connection for
the specified 'Flow tracking inactivity timeout' then the active flow tracking resource is released. The
active flow tracking resource is allocated as soon as a SYN packet is seen to mark the start of a TCP
connection.
Flow tracking inactivity timeout:
This setting controls how long an active-flow tracking resource will be allocated even though no data has
flowed through the FX for that connection. The active flow tracking resource is automatically released if
the connection is closed. The recommended standard for this setting is five days, however in many cases
in can be set lower if conservation of active flow tracking resources is important. Most TCP applications
do not have an issue with this setting because generally it doesn't matter if the active tracking resource is
released when there is no activity. However, one notable exception is FTP, which allocates both a control
connection and a data connection. If a long FTP transfer is flowing over the data port, there will not be
any data flowing over the control connection, and if the inactivity timer expires for that control
connection, the FTP transfer will cease. On the other hand, HTTP applications generally use very short-
lived connections in which active-flow resources are quickly released.
If flow capacity reached:
This setting allows you to specify the course of action the FX should take if the active flow capacity is
reached. The default "Fail-to-wire" setting is appropriate if the FX is intercepting traffic via 'in-line' mode
or 'WCCP" mode. In both of those cases, traffic will pass through the FX as though it were an Ethernet
cable. However if intercepting traffic in 'routed' mode, the 'Reject new connections' choice will be the
course of action regardless of the setting. In either case, the FX will emit an SNMP alert if the number of
active flows reaches 99% of capacity. The 'Status->WANOP Monitor' can be used to determine if the FX
'Active flow capacity' should be adjusted.
4.1.5 System Time
Network Time Server:
This setting will specify the host address for which the FX Series ADC will attempt to synchronize its time
via the "Network Time Protocol". The FX Series ADC performs this synchronization one minute following a
restart and once per week thereafter.
Time Zone:
This selector allows you to specify a time zone in which the FX Series ADC resides. In most cases, the
default value of UTC-0 (GMT) is desirable because this will facilitate correlating system events with
troubleshooting and other logs.
4.1.6 Software Updates
Automatically Distribute FX Series Remote Updates:
If "enabled", then the FX-Remote devices will periodically check to see if a newer version of firmware is
available. If so, the FX-Remote devices will automatically download and apply the firmware update. The
default value is "Disabled". It is a recommended practice that this setting be enabled only when you wish
to deploy updated FX firmware during off-peak hours.
FX Series Administration Guide - Version 6.2.2
Chapter: FX Series ADC General Settings
Section: Redundancy
107
MN-FXSERIESADM6 Rev 6
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