On-Failure Mode Parameter - Cisco SCE8000 GBE Installation And Configuration Manual

Topology-Related Parameters

On-Failure Mode Parameter

The on-failure mode parameter configures the action taken by a failed SCE platform when a failure is
detected.
As described in the section
supports three different modes. The Bypass, External Bypass, and Cutoff modes are possible when the
Cisco SCE8000 GBE is not operational due to platform failure or boot. The Forwarding mode enables
control of traffic flow and is not compatible with the non-operational status.
The following on-failure modes are possible:
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In a single Cisco SCE8000 GBE topology, the value of this parameter is determined by whether or not
the link can be completely cut when the Cisco SCE8000 GBE fails, or whether traffic flow should
continue across the link in spite of platform failure. In the latter case, the external-bypass mode is the
recommended setting, and is therefore the default value for the on-failure mode parameter.
In a cascaded Cisco SCE8000 GBE topology, the default on-failure mode is Bypass, since it preserves
full traffic processing functionality on both links in most single box failures (as long as the SPA interface
card is functioning properly).
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Cisco SCE8000 GBE Installation and Configuration Guide
3-12
Internal Bypass Mechanism, page
Bypass — The SPA interface card forwards traffic between the two ports of each link with no
intervention of the control application running in the Cisco SCE8000 GBE platform. This is also
known as 'electrical bypass'.
In a cascade setup, this allows the traffic of the link connected to the failed box to be passed to the
active box for processing.
Cutoff — There is no forwarding of traffic. The link is forced down, resulting in traffic cutoff at
Layer1.
External-bypass – The external optical bypass device is used to bypass traffic, maintaining link
continuity at all times.
Cutoff mode is suggested for the following:
Non-redundant inline topology if value-added services (such as security) are crucial and are
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more important than maintaining connectivity.
Bypass mode is suggested for the following:
When connectivity is of high importance. Note, however, that the link may be forced down for
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up to ten seconds during reboot and is not preserved on power failure.
External-bypass mode is suggested for the following:
Non-redundant inline topology if connectivity is crucial and must also be preserved on power
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failure.
Redundant inline setups, if connectivity is crucial. Note that when this mode is used, the
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serviced traffic may experience some service inaccuracy as a result of the traffic of the failing
box not being processed.
Chapter 3 Cisco SCE8000 GBE Topology and Topology-Related Parameters
3-7, the SPA Interface Processor card
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