1-4
DLDP Status
A link can be in one of these DLDP states: initial, inactive, active, advertisement, probe, disable, and
delaydown.
Table 1-2 DLDP status
Status Description
Initial Initial status before DLDP is enabled.
Inactive DLDP is enabled but the corresponding link is down
Active DLDP is enabled, and the link is up or an neighbor entry is cleared
Advertisement
All neighbors communicate normally in both directions, or DLDP
remains in active state for more than five seconds and enters this
status. It is a stable state where no unidirectional link is found
Probe
DHCP sends packets to check whether the link is a unidirectional. It
enables the probe sending timer and an echo waiting timer for each
target neighbor.
Disable
DLDP detects a unidirectional link, or finds (in enhanced mode) that a
neighbor disappears. In this case, DLDP sends and receives only
recover probe packets and recover echo packets.
DelayDown
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.
After the DelayDown timer expires, the DLDP neighbor information is
removed.
DLDP Timers
Table 1-3 DLDP timers
Timer Description
Advertisement sending
timer
Interval between sending advertisement packets, which can be
configured on a command line interface.
By default, the timer length is 5 seconds.
Probe sending timer The interval is 0.5 seconds. In the probe state, DLDP sends two probe
packets in a second.
Echo waiting timer
It is enabled when DLDP enters the probe state. The echo waiting
timer length is 10 seconds.
If no echo packet is received from the neighbor when the Echo waiting
timer expires, the state of the local end is set to unidirectional link
(one-way audio) and the state machine turns into the disable state.
DLDP outputs log and tracking information, sends flush packets.
Depending on the user-defined DLDP down mode, DLDP disables
the local port automatically or prompts you to disable the port
manually. At the same time, DLDP deletes the neighbor entry.