Black Box TS250A, Manual, Page: 56 / 64

Not seeing traffic at the analyzer from the TAP
Chapter 5 FAQ and Troubleshooting 56
rev. 1
Not seeing traffic at the analyzer from the TAP
If your TAP is not transmitting to the analyzer as you expect, check
the following:

The TAP is receiving power using a Black Box power adapter.
The Link A and Link B lights flash when there is traffic
traversing through the TAP, which indicates the TAP has
power.

The Link is definitely up and running.

The Ethernet/SPAN or Fiber channel are not diverted
elsewhere.

The cable to connect to the analyzer works. Use a different
cable to confirm this.

Try swapping the cables between the ports.

If you are using a TAP with a GigaStor, ensure the driver
configuration speed is set correctly. Sometimes allowing it to
auto-negotiate will enable the connection. This may work for
a copper connection to the analyzer. It is not recommended
for optical connections.

The correct SFPs are used if you are connecting to an optical
analyzer.

Use a light meter to verify there is enough light power with
an optical TAP.
If you have checked all of the above, then a couple of common issues
may have occurred:

If you are using an optical connection from the TAP to your
analyzer, ensure that the receive NIC on the analyzer has
auto-negotiation disabled. If auto-negotiation on the NIC is
enabled, you will not be able to see traffic from the TAP.

If the system you are monitoring is Linux or UNIX based, you
may have an issue with the Maximum Transmission Unit size.
The TCP stack in the UNIX system uses algorithms to
produce a MTU based on response time from SYN ACK. The
TAP adds about 200 nanoseconds of delay to every packet
that comes through. Typically, this small delay is not an issue
because most responses are in the millisecond range and not