HP 6125G Configuration Manual page 38

Table 12 DLDP mode and neighbor entry aging
DLDP mode
Normal DLDP
mode
Enhanced
DLDP mode
Table 13 shows the relationship between DLDP modes and unidirectional link types.
Table 13 DLDP mode and unidirectional link types
Unidirectional
link type
Cross-connected
link
Connectionless
or broken link
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
(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 8 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.
Detecting a neighbor
after the corresponding
neighbor entry ages out
No
Yes
Whether it
Whether it
occurs on
occurs on
copper twisted
fibers
pairs
Yes No
Yes Yes
Removing the neighbor
entry immediately after the
Entry timer expires
Yes
No
In which DLDP mode unidirectional links can be
detected
Both normal and enhanced modes.
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.
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Triggering the Enhanced
timer after an Entry timer
expires
No
Yes
Figure 8 may occur