9
Step Command Remarks
from the upper threshold.
Forcibly bringing up a fiber port
CAUTION:
The following operations on a fiber port will cause link updown events before the port finally stays up:
• Configure the port up-mode command and the speed or duplex command at the same time.
• Install or remove fiber links or transceiver modules after you forcibly bring up the fiber port.
IMPORTANT:
Copper ports do not support this feature.
As shown in Figure 1, a fiber port typically uses separate fibers for transmitting and receiving packets.
The physical state of the fiber port is up only when both transmit and receive fibers are physically
connected. If one of the fibers is disconnected, the fiber port does not work.
To enable a fiber port to forward traffic over a single link, you can use the port up-mode command.
This command brings up a fiber port by force, even when no fiber links or optical modules are
present. If one fiber link is present and up, the fiber port can forward packets over the link
unidirectionally.
Figure 1 Forcibly bring up a fiber port
Configuration restrictions and guidelines
When you forcibly bring up a fiber port, follow these guidelines:
Correct fiber
connection
When Ethernet interfaces
cannot be or are not
forcibly brought up
When Ethernet interfaces
are forcibly brought up
Fiber port Tx end Rx end The fiber is disconnected.Fiber link
GE1/0/1
GE1/0/1
Device A
Device B
GE1/0/1
GE1/0/1
Device A
Device B
GE1/0/1
GE1/0/1
Device A
Device B
The interface is down.Packets
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