Cisco DS-C9216I-K9, Руководство по настройке

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21-3
Cisco MDS 9000 Fabric Manager Switch Configuration Guide
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Chapter 21 Configuring Fibre Channel Routing Services and Protocols
FSPF Examples
Redundant Links
To further improve on the topology in, each connection between any pair of switches can be replicated;
two or more links can be present between a pair of switches. shows this arrangement. Because switches
in the Cisco MDS 9000 Family support PortChanneling, each pair of physical links can appear to the
FSPF protocol as one single logical link.
By bundling pairs of physical links, FSPF efficiency is considerably improved by the reduced database
size and the frequency of link updates. Once physical links are aggregated, failures are not attached to a
single link but to the entire PortChannel. This configuration also improves the resiliency of the network.
The failure of a link in a PortChannel does not trigger a route change, thereby reducing the risks of
routing loops, traffic loss, or fabric downtime for route reconfiguration.
Figure 21-2 Fault Tolerant Fabric with Redundant Links
For example, if all links are of equal speed and no PortChannels exist, the FSPF calculates four equal
paths from A to C: A1-E-C, A2-E-C, A3-D-C, and A4-D-C. If PortChannels exist, these paths are
reduced to two.
Fail-over Scenarios for PortChannels and FSPF Links
The SmartBits traffic generator was used evaluate the scenarios displayed in Figure 21-3 and
summarized in Table 21-1 and Table 21-2 . Two links between switch 1 and switch 2 exist as either
equal-cost ISLs or PortChannels. There is one flow from traffic generator 1 to traffic generator 2. The
traffic was tested at 100 utilization of 1G in two scenarios:
•
Disabling the traffic link by either physically removing the cable.
•
Shutting down either switch 1 or switch 2.
Figure 21-3 Fail-over Scenario Using Traffic Generators
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A B C
E D
1
2
3
4
Table 21-1 Physically Removing the Cable for the SmartBits Scenario
PortChannel Scenario FSPF Scenario (Equal cost ISL)
Switch 1 Switch 2
110ms (~2K frame drops) 130ms+ (~4k frame drops)
100 ms hold time when a signal loss is reported as
mandated by the standard
Traffic Generator 1 Traffic Generator 2
Switch 1 Switch 2
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