Extreme Networks ExtremeWare XOS 11.1, Manual

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Configuring Slots and Ports on a Switch
ExtremeWare XOS 11.1 Concepts Guide
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Software-Controlled Redundant Port and
Smart Redundancy
Using the software-controlled redundant port feature you can back up a specified Ethernet port
(primary) with a redundant, dedicated Ethernet port; both ports are on the same switch. If the primary
port fails, the switch will establish a link on the redundant port and the redundant port becomes active.
Only one side of the link must be configured as redundant because the redundant port link is held in
standby state on both sides of the link. This feature provides very fast path or network redundancy.
NOTE
You cannot have any Layer 2 protocols configured on any of the VLANs that are present on the ports.
Smart Redundancy is a feature that allows control over how the failover from a redundant port to the
primary port is managed. If this feature is enabled, which is the default setting, the switch attempts to
revert to the primary port as soon as it can be recovered. If the feature is disabled, the switch attempts
only to recover the primary port to active if the redundant port fails.
A typical configuration of software-controlled redundant ports is a dual-homed implementation
(
Figure 1 ). This example maintains connectivity only if the link between switch A and switch B remains
open; that link is outside the scope of the software-controlled port redundancy on switch C.
Figure 1: Dual-homed implementation for switch C
In normal operation, the primary port is active and the software redundant switch (switch C in
Figure 1 ) blocks the redundant port for all traffic, thereby avoiding a loop in the network. If the switch
detects that the primary port is down, the switch unblocks the redundant port and allows traffic to flow
through that redundant port.
NOTE
The primary and redundant ports must have identical VLAN membership.
You configure the software-controlled redundant port feature either to have the redundant link always
physically up but logically blocked or to have the link always physically down. The default value is to
have the link physically down, or Off.
By default, Smart Redundancy is always enabled. If you enable Smart Redundancy, the switch
automatically fails over to the redundant port and returns traffic to the primary port once connectivity
Switch A Switch B
Redundant
Link Primary
Link
Switch C
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