Manual
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ultra  five-kind  twisted  pair),  ULDP  can  monitor  the  link  state  of  physical  links.  Whenever  a 
unidirectional link is discovered, it will send warnings to users and can disable the port 
automatically or manually according to users’ configuration. 
The  ULDP  of  switches  recognizes  remote  devices  and  check  the  correctness  of  link 
connections via interacting ULDP messages. When ULDP is enabled on a port, protocol state 
machine  will  be  started,  which  means  different  types  of  messages  will  be  sent  at  different 
states of the state machine to check the connection state of the link by exchanging information 
with  remote  devices.  ULDP  can  dynamically  study  the  interval  at  which  the  remote  device 
sends notification messages and adjust the local TTL (time to live) according to that interval. 
Besides,  ULDP  provides  the  reset  mechanism,  when  the  port  is  disabled  by  ULDP,  it  can 
check again through reset mechanism. The time intervals of notification messages and reset in 
ULDP can be configured by users, so that ULDP can respond faster to connection errors in 
different network environments. 
The premise of ULDP working normally is that link works in duplex mode, which means ULDP 
is enabled on both ends of the link, using the same method of authentication and password. 
8.2 ULDP Configuration Task Sequence 
1.  Enable ULDP function globally 
2.  Enable ULDP function on a port 
3.  Configure aggressive mode globally 
4.  Configure aggressive mode on a port 
5.  Configure the method to shut down unidirectional link  
6.  Configure the interval of Hello messages 
7.  Configure the interval of Recovery 
8.  Reset the port shut down by ULDP 
9.  Display and debug the relative information of ULDP 
1.  Enable ULDP function globally 
Command 
Explanation 
Global configuration mode 
uldp enable 
uldp disable 
Globally enable or disable ULDP function. 
2.  Enable ULDP function on a port 
Command 
Explanation 
Port configuration mode 










