Link Auto-Recovery Mechanism - H3C S7500 Series Operation Manual

Operation Manual – DLDP
H3C S7500 Series Ethernet Switches
Table 1-8 Description on the two DLDP neighbor states
DLDP neighbor state
two way
unknown

1.2.6 Link Auto-recovery Mechanism

If the shutdown mode of a port is set to auto shutdown, the port is set to the DLDP down
state when DLDP detects the link connecting to the port is a unidirectional link. A port in
DLDP down state does not forward service packets or receive/send protocol packets
except DLDPDUs.
A port in the DLDP down state recovers when the corresponding link recovers. A port in
the DLDP down state sends recover probe packets periodically. On receiving a correct
recover echo packet (which means that the unidirectional link is restored to a
bidirectional link), it is brought up by DLDP. The detailed process is as follows.
1) A port in the DLDP down state sends a recover probe packet every 2 seconds.
Recover probe packets carry only the local port information.
2) Upon receiving a recover probe packet, the peer end responds with a recover
echo packet.
3) Upon receiving a recover echo packet, the local end checks to see if the neighbor
information carried in the recover echo packet is consistent with that of the local
port. If yes, the link between the local port and the neighbor is considered to be
recovered to bidirectional, the port changes from the disable state to the active
state, and neighboring relationship is reestablished between the local port and the
neighbor.
Note:
Only ports in the DLDP down state can send and process recover probe packets and
recover echo packets. The auto-recovery mechanism does apply to ports that are shut
down manually.
Description
The link to the neighbor operates properly.
The device is detecting the neighbor and the neighbor
state is unknown.
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Chapter 1 DLDP Configuration