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Steelhead Appliance Installation and Configuration Guide
17
Overview of the Steelhead Appliance
Overview of the Steelhead Appliance
All Steelhead appliance models and in-path network interface cards support a fail-to-wire mode. In the
event of a failure or loss of power, the Steelhead appliance goes into bypass mode and the traffic passes
through uninterrupted.
Certain in-path network interface cards also support a fail-to-block mode. In the case of a failure or loss of
power, the Steelhead appliance LAN and WAN interfaces completely lose link status. The default failure
mode is fail-to-wire mode.
If there is a serious problem with the Steelhead appliance or it is not powered on, it goes into bypass mode
to prevent a single point of failure. If the Steelhead appliance is in bypass mode, you are notified in the
following ways:
The Intercept/Bypass status light on the bypass card is triggered. For detailed information about
bypass card status lights, see
“Bypass Card Status Lights” on page 39
The Welcome page of the Management Console displays Critical in the Status bar.
SNMP traps are sent.
The event is logged to system logs (syslog).
Email notifications are sent (if you have set this option).
When the fault is corrected, new connections that are made receive optimization; however, connections
made during the fault are not. To force all connections to be optimized, enable the kickoff feature. Generally,
connections are short lived and kickoff is not necessary. For detailed information about enabling the kickoff
feature, see the Steelhead Management Console User’s Guide.
When the Steelhead appliance is in bypass mode the traffic passes through uninterrupted. Traffic that was
optimized might be interrupted, depending on the behavior of the application-layer protocols. When
connections are restored, they succeed, although without optimization.
In an out-of-path deployment, if the Steelhead appliance fails, the first connection from the client fails. After
detecting that the Steelhead appliance is not functioning, a ping channel is setup from the client-side
Steelhead appliance to the server-side Steelhead appliance. Subsequent connections are passed through
unoptimized. When the ping succeeds, processing is restored and subsequent connections are intercepted
and optimized.
For detailed information about the ping command, see the Riverbed Command-Line Interface Reference
Manual.
Fail-to-Block (Disconnect) Mode
The bypass cards listed below support fail-to-block mode in RiOS software versions prior to v5.0. With the
release of RiOS v5.0, fail-to-block functions with most NICs provided that the operating system is running.
In fail-to-block mode, if the Steelhead appliance has an internal software failure or power loss, the Steelhead
appliance LAN and WAN interfaces power down and stop bridging traffic.
When fail-to-block is enabled, a failed Steelhead appliance blocks traffic along its path, forcing traffic to be
re-routed onto other paths (where the remaining Steelhead appliances are deployed). This is only useful if
the network has a routing or switching infrastructure that can automatically divert traffic off of the link once
the failed Steelhead appliance blocks it.
Note:
You can use this with connection forwarding, the allow-failure CLI command, and an additional Steelhead
appliance on another path to the WAN to achieve redundancy. For more information, see the Riverbed Command-
Line Interface Reference Manual.