3Com Switch 7750 Configuration Guide Guide

202 CHAPTER 26: DLDP CONFIGURATION
DLDP operating mode
DLDP can operate in two modes: normal and enhanced.
Enhanced timer
In enhanced mode, if no packet is received from the
neighbor when the entry aging timer expires, DLDP enables
the enhanced timer for the neighbor. The timeout time for
the enhanced timer is 10 seconds.
The enhanced timer then sends two probe packets every one
second and totally eight packets continuously to the
neighbor.
If no echo packet is received from the neighbor when the
Enhanced timer expires, the local end is set to unidirectional
communication status and the state machine turns into
disable status. DLDP outputs log and tracking information,
and sends flush packets. Depending on the user-defined
DLDP down mode, DLDP disables the local port automatically
or prompt the user to disable the port manually. DLDP
deletes the neighbor entry.
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.
Tabl e 129 DLDP operating mode and neighbor entry aging
DLDP operating
mode
DLDP probes
neighbor during
neighbor entry
aging
Enabling entry
aging timer during
neighbor entry
aging
Enabling enhanced
timer when entry
aging timer expires
Normal mode No
Yes (the neighbor
entry ages 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 local end
is set to single pass
status, and the
neighbor entry ages)
Table 128 DLDP timers
Timer Description