H3C S3610-28P, Operation Manual, Page: 1466 / 1547

Operation Manual – DLDP
H3C S3610&S5510 Series Ethernet Switches
Chapter 1 DLDP Configuration
1-6
Table 1-3 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
The enhanced DLDP mode is designed for addressing black holes. It prevents the
cases where one end of a link is up and the other is down. If you configure the speed
and the duplex mode by force on a device, the situation shown in Figure 1-3 may occur,
where Port B is actually down but the state of Port B cannot be detected by common
data link protocols, so Port A is still up. In enhanced DLDP mode, however, Port A tests
Port B after the Entry timer concerning Port B expires. Port A then transits to the
Disable state if it receives no Echo packet from Port A when the Echo timer expires. As
Port B is physically down, it is in the Inactive DLDP state.
Figure 1-3 A case for Enhanced DLDP mode
Note:
z
In normal DLDP mode, only fiber cross-connected unidirectional links (as shown in
Figure 1-1 ) can be detected.
z
In enhanced DLDP mode, two types of unidirectional links can be detected. One is
fiber cross-connected links (as shown in Figure 1-1 ). The other refers to fiber pairs
with one fiber not connected or disconnected (as shown in Figure 1-2 ). To detect
unidirectional links that are of the latter type, you need to configure the ports to
operate at specific speed and in full duplex mode. Otherwise, DLDP cannot take
effect. When a fiber of a fiber pair is not connected or gets disconnected, the port
that can receive optical signals is in Disable state; the other port is in Inactive state.