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Cisco SCE 2000 4xGBE Installation and Configuration Guide
OL-7824-07
Chapter 3 Information About Topology
Information About Topology Considerations
Redundancy
When a high degree of reliability is desired, a second SCE 2000 platform should be installed to provide
backup operation capabilities. The combination of two SCE 2000s guarantees uninterrupted functioning
in case of a failure of one of the platforms. The two SCE 2000s are cascaded, so that, although all
processing is performed only in the active SCE 2000, the standby SCE 2000 is constantly updated with
all the necessary information so that it can instantly take over processing the traffic on the data links
should the active SCE 2000 fail.
If only preservation of the network links is required, and uninterrupted functionality of the SCE 2000 is
not required, a single SCE 2000 is sufficient.
Information About Link Continuity
The bypass mechanism of the SCE 2000 allows traffic to continue to flow, if desired, even if the device
itself is not functioning.
Note that when the SCE 2000 is connected to the network through an optical splitter, a failure of the SCE
2000 does not affect the traffic flow, as the traffic continues to flow through the optical splitter.
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Maintaining the Network Links vs. Maintaining SCE 2000 Platform Functionality, page 3-3
Bypass Mechanism
The SCE 2000 includes a Network Interface Card with a bypass mechanism that is enabled upon SCE
2000 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:
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Bypass
— The bypass mechanism preserves the network link, but traffic is not processed for
monitoring or for control.
•
Forwarding
— This is the normal operational mode, in which the SCE 2000 processes the traffic
for monitoring and control purposes.
•
Sniffing
— The bypass mechanism preserves the network link, while in parallel allowing the SCE
2000 to process the traffic for monitoring only.
•
Cutoff
— There is no forwarding of traffic, and the physical link is forced down (cutoff
functionality at layer 1).
Maintaining the Network Links vs. Maintaining SCE 2000 Platform Functionality
When a single SCE 2000 is deployed, the user may decide that in case of a failure, maintaining the
network link is more important than providing the SCE 2000 functionality. In this scenario, when the
SCE 2000 detects a failure that requires a reboot process for recovering, it immediately switches to
Bypass mode, allowing all traffic to bypass the SCE 2000. The SCE 2000 stays in Bypass mode
maintaining the network link, albeit without SCE 2000 processing, until the SCE 2000 fully recovers
from the failure and is ready to resume normal functioning.
