R3102-R3103-HP 6600/HSR6600 Routers High Availability Configuration Guide

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Packet type
Processing procedure
LinkDown packet
Checks whether the
local port operates
in Enhanced mode.
If yes and the local port is not in Disable state, sets the state of
the neighbor to one way, and then checks the state of other
neighbors to determine the subsequent action to take:
 If all the neighbors are in one way state, changes the local
DLDP port state to Disable.
 If the state of some neighbors is still unknown, takes no
action until the state of these neighbors is determined.
 If any two-way neighbor is present, removes all one-way
neighbors, but does not change the DLDP port state.
If no, no process is performed.
3. If no echo packet is received from a neighbor, DLDP takes action as described in Table 16.
Table 16 Action to take when no echo packet is received from a neighbor
No echo packet received from the neighbor
Action
In normal mode, no echo packet is received
when the Echo timer expires.
DLDP sets the state of the neighbor to one way, and
determines the subsequent action to take depending on the
state of the other neighbors:
 If all the neighbors are in one way state, removes all the
neighbor entries, changes the DLDP port state to
Disable, outputs log and tracking information, and
sends Disable packets to the neighbors. In addition,
depending on the user-defined DLDP down mode, shuts
down the local port or prompts users to shut down the
port.
 If the state of some neighbors is unknown, takes no
action until the state of these neighbors is determined.
 If a two-way neighbor is present, removes all the
one-way neighbors, but does not change the DLDP port
state.
In enhanced mode, no echo packet is received
when the Echo timer expires.
Link auto-recovery mechanism
If the port shutdown mode upon detection of a unidirectional link is set to auto, DLDP automatically
sets the state of the port where a unidirectional link is detected to DLDP down. A DLDP down port
cannot forward data traffic or send/receive any PDUs except DLDPDUs.
On a DLDP down port, DLDP monitors the unidirectional link. Once DLDP finds out that the state of the
link has been restored to bidirectional, it brings up the port.
The DLDP down port sends out a RecoverProbe packet every2 seconds, which carries only information
about the local port. Upon receiving the RecoverProbe packet, the remote end returns a RecoverEcho
packet. Upon receiving the RecoverEcho packet, the local port checks whether neighbor information
in the RecoverEcho packet is the same as the local port information. If they are the same, the link
between the local port and the neighbor is considered to have been restored to a bidirectional link,
and the port will transit from Disable state to Active state and re-establish relationship with the
neighbor.
Only DLDP down ports can send and process Recover packets, including RecoverProbe packets and
RecoverEcho packets. If related ports are manually shut down with the shutdown command, the
auto-recovery mechanism will not take effect.