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Chapter 3 Topology
Issues to Be Considered
Cisco SCE 1000 2xGBE Installation and Configuration Guide
3-2 OL-7821-05
SCE Platform Configuration
There are four topology-related parameters:
• Connection mode — Can be Inline or Receive-only, depending on the physical installation of
the SCE 1000:
May be configured via either the setup command or the connection-mode command.
• Bypass mode when the SCE 1000 is not operational (on-failure) — This parameter
determines whether the system cuts the traffic or bypasses it when the SCE 1000 has failed.
May be configured via either the setup command or the connection-mode command.
• Status after reboot caused by fatal error or abnormal shutdown — This parameter
determines whether the SCE 1000 returns to normal operational state after a failure.
May be configured via either the setup command or the failure-recovery
operation-mode command.
• Link failure reflection — This parameter determines the behavior of the system when there
is a link problem. In some topologies it is required that link failure on one port be reflected to
the other port, to allow the higher layer redundancy protocol in the network to function
correctly.
May be configured via the link failure-reflection command only.
Failure Detection Mechanism
The SCE 1000 contains various mechanisms to monitor the status and to detect failures. The main
mechanisms are:
• Boot time diagnostics failure. When there is a failure in diagnostics testing at boot time the
system will remain in failure status.
• Watchdog mechanism. There are two types of watchdogs:
• HW watchdog. A hardware mechanism that detects control entity failure.
• SW watchdog. A software mechanism that periodically checks for software failures in the
SCE 1000. If a failure is detected, an error massage is sent and the SCE 1000 reboots.
• Run time hardware tests. The system periodically tests the hardware components for error. If a
hardware component is malfunctioning, it will be discovered by the system within seconds.
Bypass Mechanism
The SCE 1000 includes a Network Interface Card with a bypass mechanism that is enabled upon
SCE 1000 failure. In addition, when connected in-line it can also be enabled in normal operation
to simultaneously bypass traffic flow to the other side and direct it internally for analysis. In this
case it maintains "receive-only"-like monitoring functions, when control functionality is not
required.
The bypass card supports the following four modes:
• Bypass — The bypass mechanism preserves the network link, but traffic is not processed for
monitoring or for control.