3Com 3C17205-US - Corp SUPERSTACK 3 SWITCH 4400..., Implementation Manual

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46 C
HAPTER
4: U
SING
R
ESILIENCE
F
EATURES
Resilience Feature
Overview
Resilient links and STP/RSTP cannot both be used on the network at the
same time. Table 3 lists the key differences between each feature, so you
can evaluate the benefits of each to determine which feature is most
suitable for your network.
Table 3 Resilient Links and Spanning Tree Protocols — Key Differences
3Com recommends that you use the Rapid Spanning Tree Protocol
feature (default enabled) to provide optimum performance for your
network and ease of use.
The Switch also supports aggregated links which increase bandwidth and
also provide resilience against individual link failure. Aggregated links will
operate with STP enabled, but will not operate on ports that are part of a
resilient link pair. For more information, see
Aggregated Links on
page 29 .
What are Resilient
Links?
The resilient link feature enables you to protect critical links and prevent
network downtime if those links fail. A resilient link is comprised of a
resilient link pair containing a main link and a standby link. If the main
link fails, the standby link quickly and automatically takes over the task of
the main link and becomes the “active link”.
The resilient link pair is defined by specifying a main port and a standby
port at one end of the link. During normal operation, the main port is
enabled and the standby port is disabled. If the main link fails, the main
port is disabled and the standby port is enabled. If the main link becomes
operational, you can then re-enable the main port and disable the
standby port again.
There are two user configurable modes of operation for resilient links:
Resilient Links Spanning Tree Protocol
Rapid Spanning Tree
Protocol
User configures each
Switch separately. STP is disabled by default.
User enables STP on each
Switch. RSTP is enabled by default.
Manual configuration. Automatic configuration. Automatic configuration.
Within 5 seconds restores
an active connection from
a standby link. Up to 30 second delay on
link failure to restoring a
network connection. Within 5 seconds restores
a network connection.