Manual

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Москва, Новозаводская ул., 18, стр. 1
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4.3 ULDP Function Typical Examples
Fiber Cross Connection
In the network topology in Graph, port g1/0/1 and port g1/0/2 of switch A as well as port g1/0/3
and port g1/0/4 of switch B are all fiber ports. And the connection is cross connection. The
physical layer is connected and works normally, but the data link layer is abnormal. ULDP can
discover and disable this kind of error state of link. The final result is that port g1/0/1, g1/0/2 of
switch A and port g1/0/3, g1/0/4 of switch B are all shut down by ULDP. Only when the
connection is correct, can the ports work normally (won’t be shut down).
Switch A configuration sequence:
SwitchA(config)#uldp enable
SwitchA(config)#interface ethernet 1/0/1
SwitchA (Config-If-Ethernet1/0/1)#uldp enable
SwitchA (Config-If-Ethernet1/0/1)#exit
SwitchA(config)#interface ethernet1/0/2
SwitchA(Config-If-Ethernet1/0/2)#uldp enable
Switch B configuration sequence:
SwitchB(config)#uldp enable
SwitchB(config)#interface ethernet1/0/3
SwitchB(Config-If-Ethernet1/0/3)#uldp enable
SwitchB(Config-If-Ethernet1/0/3)#exit
SwitchB(config)#interface ethernet1/0/4
SwitchB(Config-If-Ethernet1/0/4)#uldp enable
As a result, port g1/0/1, g1/0/2 of switch A are all shut down by ULDP, and there is notification
information on the CRT terminal of PC1.
%Oct 29 11:09:50 2007 A unidirectional link is detected! Port Ethernet1/0/1 need to be shutted
down!
g1/0/2
Switch B
g1/0/4
g1/0/3
g1/0/1
Switch A
PC1
PC2