3Com Switch 7750 Configuration Guide

218 CHAPTER 27: DLDP CONFIGURATION
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.
n
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.
DLDP Configuration
Configuring DLDP
n
For a port with DLDP enabled, you are not recommended to execute the port
monitor last command on the port. If it is necessary, the value argument in this
command must be less than 10.
The following table describes the DLDP configuration tasks:
Table 150 DLDP configuration tasks
Operation Command
Descriptio
n
Enter system view system-view -
Enable DLDP Enable DLDP globally dldp enable Required.
Enable
DLDP
globally
and then
enable
DLDP on
the
specified
port.
Enable DLDP
on a port
Enter Ethernet
port view
interface interface-type
interface-number
Enable DLDP on a
port
dldp enable