Westermo RedFox Series - Manual (Page 331)

Westermo OS Management Guide
Version 4.17.0-0
15.1.3 Active uplink election
Both FRNT Ring Coupling and Multi-Link Dual Homing makes use of an uplink elec-
tion mechanism to determine which of the available uplink that should become
active and which should be backups. For Dual-Homing, the election is handled
within the dual-homing node itself, but for FRNT ring coupling the election pro-
cess the RiCo nodes in the FRNT ring negotiate which uplink should be active.
To determine which uplink is preferred, an cost vector is formed for every uplink
and compared. The uplink with the lowest cost vector is elected as active uplink
1 .
The cost vector consists of the following fields.
❼ Link speed/duplex Cost: The most significant component of the cost vec-
tor depends on the link’s speed and duplex setting. This link speed/duplex
component is calculated as shown in
table 15.2 , similar to link cost calcu-
lation in RSTP (see section 16.1.3 ). It is also possible to configure the link
speed/duplex cost manually. Default: Auto (see table 15.2 )
❼ Priority: The next component of the cost vector is the uplink priority, which
is used when two or more uplinks have the same link speed/duplex cost.
Then the uplink with the lowest priority value is elected as active uplink.
Default: 128
❼ Base MAC address: (Only for Ring Coupling) If link speed/duplex cost and
uplink priority are equal for two RiCo nodes, the node with the lowest base-
MAC address will win.
❼ Link/port identity: Finally, if all other components are equal, the port with
the lowest port number is elected as active.
Bandwidth Full Duplex Half Duplex Two Aggregated Links
10 Mbps 2,000,000 4,000,000 1,000,000
100 Mbps 200,000 400,000 100,000
1 Gbps 20,000 40,000 10,000
Table 15.2: Link speed & duplex to link cost component translation table. For
aggregated links (see
chapter 17 ) the link speed/duplex cost is half the cost of
a single link for the given link speed and duplex mode. This is shown in the
right-most column.
1 The exception is dual-homing with synchronised dual-homing enabled. Then uplinks to FRNT
rings with reachable Ring Coupling nodes have precedence over other uplinks, see also sec-
tion 15.1.2.1 .
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