Concept Guide

T - Increase refresh interval t - Decrease refresh interval
q - Quit
q
DellEMC#
Maintenance Using TDR
The time domain reectometer (TDR) is supported on all Dell EMC Networking switches.
TDR is an assistance tool to resolve link issues that helps detect obvious open or short conditions within any of the four copper pairs. TDR
sends a signal onto the physical cable and examines the reection of the signal that returns. By examining the reection, TDR is able to
indicate whether there is a cable fault (when the cable is broken, becomes unterminated, or if a transceiver is unplugged).
TDR is useful for troubleshooting an interface that is not establishing a link; that is, when the link is apping or not coming up. TDR is not
intended to be used on an interface that is passing trac. When a TDR test is run on a physical cable, it is important to shut down the port
on the far end of the cable. Otherwise, it may lead to incorrect test results.
NOTE: TDR is an intrusive test. Do not run TDR on a link that is up and passing trac.
To test and display TDR results, use the following commands.
1 To test for cable faults on the TenGigabitEthernet cable.
EXEC Privilege mode
tdr-cable-test tengigabitethernet slot/port
Between two ports, do not start the test on both ends of the cable.
Enable the interface before starting the test.
Enable the port to run the test or the test prints an error message.
2 Displays TDR test results.
EXEC Privilege mode
show tdr tengigabitethernet slot/port
Link Dampening
Interface state changes occur when interfaces are administratively brought up or down or if an interface state changes.
Every time an interface changes a state or aps, routing protocols are notied of the status of the routes that are aected by the change in
state. These protocols go through the momentous task of re-converging. Flapping; therefore, puts the status of entire network at risk of
transient loops and black holes. Dampening limits the notication of status to the routing protocols. Link dampening minimizes the risk
created by apping by imposing a penalty (1024) for each interface ap and decaying the penalty exponentially based on the half-time.
When the accumulated penalty exceeds a certain threshold (suppress threshold), the interface is put in an Error-Disabled state and for all
practical purposes of routing, the interface is deemed to be “down.” After the interface becomes stable and the penalty decays below a
certain threshold (reuse threshold), the interface comes up again and the routing protocols re-converge.
You congure link dampening using the dampening [[[[half-life] [reuse-threshold]] [suppress-threshold]]
[
max-suppress-time]] command on the interface.
Following is the detailed explanation of interface state change events:
• suppress-threshold— The suppress threshold is a value that triggers a apping interface to dampen. The system adds penalty
when the interface state goes up and down. When the accumulated penalty reaches the default or congured suppress threshold, the
interface state changes to Error-Disabled state. The range of suppress threshold is from 1 to 20000. The default is
2500.
Interfaces
365