3-6 SR3 SERIES PROTECTIVE RELAY PLATFORM – COMMUNICATIONS GUIDE
350 REDUNDANCY OPTIONS CHAPTER 3: ETHERNET INTERFACE
NOTE:
In case of a link loss, only port A generates an "Ethernet Link Failure" target message or
event message. Port B does not generate this message. In cases where a 350 device is
connected between 2 other devices and has a link failure on Port B, it will be necessary to
check the device connected to port B in order to identify the link failure.
350 LLA (Link Loss Alert)
Under Link Loss Alert (LLA) redundancy, port A has the priority. If the Port A LLA detects a
problem with the link, communications is switched to Port B. Port B is, in effect, acting as a
redundant or backup link to the network for Port A.
The operation of ports A and B are as follows:
Ports A and B both use the Port A MAC and IP address settings, while Port B is in standby
mode in that it does not actively communicate on the Ethernet network but does monitors
its Ethernet link.
If the setting LLA PRIORITY is enabled:
• The primary port is port A while secondary (redundant) port is port B.
• The primary port will always be used if available.
• If the link on primary port is lost switch over to secondary port occurs immediately.
• When the link on primary port is detected again, it is monitored for a period of time
(LLA TIMEOUT) to ensure the health of the network. After that period the
communication switch over to primary port automatically.
If the setting LLA PRIORITY is disabled:
• There is no priority, therefore there is no primary port. The communication switch over
from one Port to the other occurs when the link fails.
• In this case the LLA TIMEOUT setting does not act.
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