38
State Indicates…
Advertisement
All neighbors are bi-directionally reachable or DLDP has been in active state for
more than five seconds. This is a relatively stable state where no unidirectional link
has been detected.
Probe
DLDP enters this state if it receives a packet from an unknown neighbor. In this state,
DLDP sends packets to check whether the link is unidirectional. As soon as DLDP
transits to this state, a probe timer starts and an echo timeout timer starts for each
neighbor to be probed.
Disable
A port enters this state when:
•
A unidirectional link is detected.
•
The contact with the neighbor in enhanced mode gets lost.
In this state, the port does not receive or send packets other than DLDPDUs.
DelayDown
A port in the Active, Advertisement, or Probe DLDP link state transits to this state
rather than removes the corresponding neighbor entry and transits to the Inactive
state when it detects a port-down event. When a port transits to this state, the
DelayDown timer is triggered.
DLDP timers
Table 11
DLDP timers
DLDP timer
Description
Active timer
Determines the interval for sending Advertisement packets with RSY tags, which
defaults to 1 second. By default, a switch in the active DLDP link state sends one
Advertisement packet with RSY tags every second. The maximum number of
advertisement packets with RSY tags that can be sent successively is 5.
Advertisement timer
Determines the interval for sending common advertisement packets, which defaults
to 5 seconds.
Probe timer
Determines the interval for sending Probe packets, which defaults to 1 second. By
default, a switch in the probe state sends two Probe packets every second. The
maximum number of Probe packets that can be sent successively is 10.
Echo timer
This timer is set to 10 seconds. It is triggered when a switch transits to the Probe
state or when an enhanced detect is launched. When the Echo timer expires and no
Echo packet has been received from a neighbor device, the state of the link is set to
unidirectional and the switch transits to the Disable state. In this case, the switch
does the following:
•
Sends Disable packets.
•
Either prompts the user to shut down the port or shuts down the port
automatically (depending on the DLDP down mode configured).
•
Removes the corresponding neighbor entries.
Entry timer
When a new neighbor joins, a neighbor entry is created and the corresponding
entry timer is triggered. When a DLDP packet is received, the switch updates the
corresponding neighbor entry and the entry timer.
In normal mode, if no packet is received from a neighbor when the corresponding
entry timer expires, DLDP sends advertisement packets with RSY tags and removes
the neighbor entry.
In enhanced mode, if no packet is received from a neighbor when the Entry timer
expires, DLDP triggers the enhanced timer.
The setting of an Entry timer is three times that of the Advertisement timer.