3Com Switch 7750 Configuration Guide Guide

204 CHAPTER 26: DLDP CONFIGURATION
Precautions During DLDP
Configuration
■ DLDP does not work on a port where you configure duplex and rate forcibly,
such as 10 GE port.
■ DLDP works only when the link is up.
■ To insure that DLDP neighbors can be established properly and unidirectional
links can be detected, you must make sure: DLDP is enabled on both ends, and
the interval of sending DLDP advertisement packets, authentication mode and
password are consistent on both ends.
■ You can adjust the interval of sending DLDP advertisement packets (which is 10
seconds by default and in the range of 5 seconds to 100 seconds) in different
network circumstances, so that DLDP can respond rapidly to link failure. The
interval must be shorter than one-third of the STP convergence time, which is
generally 30 seconds. If too long an interval is set, an STP loop may occur
before DLDP shut down unidirectional links. On the contrary, if too short an
interval is set, network traffic increases, and port bandwidth is reduced.
■ DLDP is also applicable to Discarding ports. Ports discarded by STP can set up
normal DLDP neighbors and detect unidirectional links.
■ DLDP does not process any LACP event, and treats each link in the aggregation
group as independent.
■ The mandatory duplex mode must be enabled on both ends of the DLDP link.
In this way, unidirectional links will be reported and the ports can be shut down
as required; if the auto-negotiation duplex mode is configured on both ends,
unidirectional links will not be reported and ports will not be shut down, while
only the state of DLDP neighbors changes.
■ If DLDP is enabled after unidirectional links appear, DLDP cannot detect
unidirectional links.
■ DLDP can detect only the two optical interfaces connected through an optical
fiber directly, and DLDP cannot be used cross devices.
■ DLDP cannot be used together with similar protocols of other companies, that
is, you cannot enable DLDP on one end and enable one of the similar protocols
of other companies.
Tabl e 132 Processing procedure when no echo packet is received from the neighbor
No Echo packet received
from the neighbor
Processing procedure
In normal mode, no echo
packet is received when
the echo waiting timer
expires
DLDP turns into disable status. It outputs log and tracking
information, sends flush packets. Depending on the user-defined
DLDP down mode, DLDP disables the local port automatically or
prompt the user to disable the port manually. DLDP sends the RSY
message and deletes the neighbor entry.
In enhanced mode, no
echo packet is received
when the enhanced timer
expires