Choosing crossover or straight-through cables
Chapter 8: Troubleshooting 25
3.
If Link B is up, then re-establish the connection. If Link B is still down, then
shut down Link A.
4.
Go to first step.
Figure 6: Cabling Failover Devices
This figure is for illustrative purposes and may not match your product.
Choosing crossover or straight-through cables
When choosing whether to use crossover or straight-through cables with a TAP,
consider the following:
♦
Crossover or straight-through cables can be used for any TAP having
copper ports; either type will operate perfectly. However, straight-through
cables are required for the 10/100 Copper TAP
only
.
♦
Most networking hardware supports
Auto-MDIX
, which electrically creates
a crossover connection where one is needed. For those devices, the proper
cable configuration is used automatically regardless of the connection
type.
♦
If you encounter any rare issue with cable choice and your TAP, test your
TAP with the opposite cable type and then contact VIAVI Support.
Typically, when a TAP is installed the existing cable that connects one device to
another is used as half of the link. That is, the existing cable connects one device
to the TAP and a new cable connects the TAP to the second device. The new,
second cable is generally a crossover cable. If the new cable is not a crossover
cable, then your endpoint devices may not be able to re-establish a connection if
the TAP loses power.
Symptom:
The TAP and endpoint devices work fine while the TAP has power, but
when power is removed the endpoints do not reconnect as they should.
Cause:
It is likely that you are using two straight-through cables. In other words,
the existing cable that connected your network devices is a straight-through
cable and the new cable you added is also a straight-through cable. This is not
a problem so long as the TAP has electricity because the TAP takes care of the
switching; however, when power is lost the TAP cannot perform the switching
and must rely on the cables themselves to do it. Straight-through cables are not
capable of
Auto-MDIX
, and because they are not the endpoint devices cannot
connect through the TAP. Another cause is that Auto-MDIX has been deliberately
turned off.
Solution:
If Auto-MDIX is turned off in your network, enable it. If Auto-MDIX
is enabled, then at least one cable must be a crossover cable; both cannot be
