Allied Telesis AT-PC232/POE, Руководство по установке

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AT-PC232/POE Media Converter Installation Guide
21
Operating Modes
The AT-PC232/POE Media Converter supports these operating modes:
ˆ
“Link Test Mode,” next
ˆ
“MissingLink Mode” on page 21
ˆ
“Smart MissingLink Mode” on page 22
Link Test Mode
Contrary to its name, the Link Test operating mode is not a diagnostic
utility. Instead, it uses the Link LEDs to display the current states of the
ports. A port’s Link LED will be on when the port has established a link to a
network device and it will be off when the port does not have a link to a
network device.
This operating mode is typically used when the network devices
connected to the ports of the media converter cannot take advantage of
the features of the MissingLink mode, or when you want to use the Link
LEDs to troubleshoot a network problem. This operating mode is also
useful after the installation of the media converter to verify whether or not
the ports on the unit have established links to their network devices.
MissingLink
Mode
The MissingLink
TM
mode allows the two ports on the media converter to
share their “link” status with each other. If one of the ports is unable to
establish a link with its network device or loses the link, this operating
mode disables the transmitter on the other port. This action notifies the
network device connected to the port that there is a loss of the link on the
other port. Without the MissingLink mode, a network device connected to a
port would be unaware of a loss of a link on the companion port, because
its link to the media converter would be unaffected. To explain it another
way, the MissingLink mode will not allow a port to form a link with its
network device unless the other port on the media converter can also
establish a link with its device.
When the link is reestablished on a port, the MissingLink mode
automatically reactivates the transmitter on the companion port so that the
two network devices can again forward traffic to each other through the
two ports of the media converter.
The value to this type of fault notification is that some network devices,
such as managed Fast Ethernet switches, can respond to the loss of a link
on a port by performing a specific action. For example, the network device
might send a trap to a network management station, and so alert the
network administrator of the problem. Or, if the device is running a
spanning tree protocol, it might seek a redundant path to a disconnected
node.
Here is an example of how the MissingLink mode works. Assume that the
two ports on a media converter are connected to two Fast Ethernet