H3C Technologies H3C S10500 Series Switches - Manual (Page 43)

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Table 12 DLDP mode and neighbor entry aging
DLDP mode
Detecting a neighbor
after the corresponding
neighbor entry ages out
Removing the neighbor
entry immediately after the
Entry timer expires
Triggering the Enhanced
timer after an Entry timer
expires
Normal DLDP
mode
No Yes No
Enhanced
DLDP mode
Yes No Yes
Table 13 shows the relationship between DLDP modes and unidirectional link types.
Table 13 DLDP mode and unidirectional link types
Unidirectional
link type
Whether it
occurs on
fibers
Whether it
occurs on
copper twisted
pairs
In which DLDP mode unidirectional links can be
detected
Cross-connected
link
Yes No Both normal and enhanced modes
Connectionless
or broken link
Yes Yes
Only enhanced mode. The port that can receive
signals is in Disable state, and the port that does not
receive signals is in Inactive state.
Enhanced DLDP mode is designed for addressing black holes. It prevents situations where one end of a
link is up and the other is down.
If you configure forced speed and full duplex mode on a port, the situation shown in
Figure 10 may occur
(take the fiber link for example). Without DLDP enabled, the port on Device B is actually down but its state
cannot be detected by common data link protocols, so the port on Device A is still up. However, in
enhanced DLDP mode, the following occurs:
The port on Device B is in Inactive DLDP state because it is physically down.
The port on Device A tests the peer port on Device B after the Entry timer for the port on Device B expires.
The port on Device A transits to the Disable state if it does not receive an Echo packet from the port on
Device B when the Echo timer expires.
Figure 10 A scenario for the enhanced DLDP mode
DLDP authentication mode
You can use DLDP authentication to prevent network attacks and illegal detection. There are three DLDP
authentication modes.