3Com Switch 7750 Configuration Guide

DLDP Fundamentals 217
DLDP Operating Mode DLDP can operate in two modes: normal and enhanced.
DLDP Neighbor State A DLDP neighbor can be in one of these two states: two way and unknown. You
can check the state of a DLDP neighbor by using the display dldp command.
DelayDown timer When a device in the active,
advertisement, or probe DLDP state
receives a port down message, it does not
removes the corresponding neighbor
immediately, neither does it changes to
the inactive state. Instead, it changes to
the delaydown state first.
When a device changes to the delaydown
state, the related DLDP neighbor
information remains, and the DelayDown
timer is triggered. The DelayDown timer is
configurable and ranges from 1 to 5
seconds.
A device in the delaydown state only
responds to port up messages.
A device in the delaydown state resumes
its original DLDP state if it receives a port
up message before the delaydown timer
expires. Otherwise, it removes the DLDP
neighbor information and changes to the
inactive state.
Table 147 DLDP timers
Timer Description
Table 148 DLDP operating mode and neighbor entry aging
DLDP operating
mode
DLDP detects
whether neighbors
exist or not when
neighbor tables are
aging
The entry aging
timer is enabled or
not during neighbor
entry aging
The enhanced
timer is enabled
or not when the
entry aging timer
expires
Normal mode No Yes (The neighbor
entry ages out after
the entry aging timer
expires)
No
Enhanced mode Yes Yes (The enhanced
timer is enabled after
the entry aging timer
expires)
Yes (When the
enhanced timer
expires, the state of
the local end is set
to unidirectional
link, and the
neighbor entry is
aged out.)
Table 149 Description on the two DLDP neighbor states
DLDP neighbor state Description
two way The link to the neighbor operates properly.
unknown The device is detecting the neighbor and
the neighbor state is unknown.