Failure In The Cascade Connection - Cisco SCE 8000 10GBE Software Configuration Manual

Chapter 11 Redundancy and Failover
In the active platform, the hardware crash mode behavior is exactly the same as on a standby platform.
The active platform assumes that when it fails, the standby platform will take over and process the traffic.
If the standby platform has failed, failure of the active platform means that the entire system has failed
(this state is also called a 'second failure'). The hardware crash mode behavior in the active platform in
this case depends on the configuration of the on-failure parameter, which determines whether traffic is
bypassed via the external bypass, if installed, maintaining traffic flow through one link, although with
no processing, or whether traffic is completely cut off.
If the standby platform has failed and the on-failure configuration is bypass or external-bypass,
hardware crash mode behavior in the active platform is as follows:
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Since neither platform is operational at this point, there is no processing taking place and traffic is simply
bypassed via the external optical bypass. If external optical bypass modules are not installed, traffic is
cut off.
If the standby platform has failed and the on-failure configuration is cutoff, hardware crash mode
behavior in the active platform is as follows:
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Since neither platform is operational at this point, there is no processing taking place. In addition,
although traffic reaches the platform, since the internal bypasses as well as all the ports are disabled, this
results in a 'dead end' , cutting off all traffic on both links.

Failure in the Cascade Connection

The effect of a failure in the cascade connection between the two Cisco SCE platforms depends on
whether one or both connections fail:
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Installing a Cascaded System
This section outlines the installation procedures for a redundant solution with two cascaded Cisco SCE
platforms.
OL-30621-02
The external optical bypass is activated (traffic is bypassed via the external bypass).
The electrical bypass is enabled between ports 0 and 1. (This is a special configuration, done just in
case the optical bypass device does not function, which has a very low probability)
The SPA modules are enabled (all ports and links are functioning)
The external optical bypass, if installed, is deactivated (traffic is sent to the platform).
The electrical bypass is disabled (cascade ports do not transmit traffic to the standby platform since
it is also not operational)
The SPA modules are disabled (ports and links are not functioning)
Only one cascade connection is down—In this case, both Cisco SCE platforms can still
communicate, so each still knows the status of the peer.
As long as one cascade connection remains up, the standby will cut off its traffic links so that all
traffic is routed via the active Cisco SCE platform. Therefore, split flow is avoided, but at the
expense of half line capacity.
Both cascade links are down—In this case, neither Cisco SCE platform knows anything about the
status of the peer. Each platform then works in standalone mode, which means that each Cisco SCE
platform processes on its own traffic only. This results in split flows.
Cisco SCE 8000 10GBE Software Configuration Guide
Hot Standby and Failover
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