Gbit Copper Tapping

Issues if you want to tap Gbit copper links


Full passive taping of Gbit Ethernet Copper links ! This is not possible !
Why ? In 10 and 100 Mbit it is possible!

The explanation is simple, the RJ45 cable has 8 wires paired to 4 groups, in 10/100 mode two of this groups are for each direction. So it is easy to connect with a device on each of the two directions and tap the traffic.

But in Gbit the situation is fully different!

General Information:
to transport 1 Gbit traffic full duplex (1 Gbit in each direction) a very complex signal is used to reach the performance and the quality. In case of Gbit Ethernet the signal is called 8/10 modulation meaning that at the same time on each cable pair 5 bits are transported. But this happens at the same time in both directions. The PHY chips at the end of each cable has a very complex work to do because it must separate the two signals from each other. This is possible because it knows its on signal, so it deduct its on send signal from the mixed signal on the line, an than it understand, the information sent by its link partner. These few sentences describe in a simplified way a very complex function, there are some more vital functions necessary (autoneg, clock ..) to establish a Gbit full duplex connection over a copper cable.

Currenct Solution:

Now to tap a copper link shown in the picture bellow it is not possible to look in the middle on the wire because all what you will see is a complex modulation of two signals. The only way to terminate the signal (see picture) is to use a PHY chip to separate the signal and then send the signal out again to the link partner. This solution is working but there are some problems coming up with this solution.
1:) It is not passive any longer in the case of a failure the link can go down and the services on the link are interrupted. To minimize this problem each copper tap has a bypass switch (relays) which close in a power down situation (see picture) to bring back the link. Also this solution will not prevent that the link is down for min 3 sec. This 3 sec result in the autoneg behaviour. This can not be changed because it is a vital functionality of IEEE 802.3 standard described in clause 28 & 40. Even this short interruption time could cause big problems in a network,

a:) because in some cases this links can not be re-established without shutting down the service
b:) re routing functions in the network will take place
c:) streaming applications will collapse and cause many issue more,

2:) Some layer 1 informations are not transported over a copper tap: for example pause frames
3:) The clock synchronisation is affected. Sync-E over a standard Gbit copper Tap is not possible, and
IEEE 1588 is affected because of the additional delay what a copper Tap produces.


Gbit Copper Tapping
  • Tags: copper tap

Author; Christian Ferenz Categories: Layer 1

About the Author

Christian Ferenz

Christian Ferenz

Leave a comment

You are commenting as guest.

Cubro Solutions


You can enlarge the transfer range of your media dramatically without risking errors on your data. The examples below show some common options, but a lot more combinations are possible.

Packetmaster as Patchfield

The Packetmaster EX can be used as intelligent patch field. This is feature is possible because the EX has no designated in and out port configuration. Each port is an input and an output at the same time.

100 Gbit LR4 multiple splitting

Sometimes it is needed to tap a 100 Gbit LR4 link more than one time, this is not easy because the optical budget is too small to do that.

384 x 10 Gbit ports cross connect

We use 6 Packetmaster EX 20400 to realize this 384 x 10 Gbit port cross connect !

  • 400 Gbit backbone
  • tunneling via VXLAN
  • non blocking
  • any to any & many to any & any to many support
  • easy expandable


Cubro NPB units support bypass function

The Cubro Bypass Application is a superior way to provide a fail-safe access port for an in-line monitoring appliance. From EX2 with Gbit up to EX 20400 with 100 Gbit bypass feature. With and without optical layer 1 switch support.


Aggregation of two 10 Gbit span ports to 1 10 Gbit output with EX2+

This application is normally not possible because the EX2+ has only two 10 Gbit ports and you need 3 to do this job.  But we at Cubro give our units some extra features to do this with two ports.

A optical ports has an transmitter and a receiver part, this two “ports” can be used separately in all Cubro NPB. The other feature what you need is the optical tap at the back.

aggregation 40 x 10 Gbit links with one EX 20400

Cubro now offers a "NEW" Packetmaster solution with 80 x 10 Gbit Ethernet ports.
The base unit is the EX 20400 with a new firmware that gives us the possibility to convert
a 40 Gbit port into 4 independent 10 Gbit ports.

Stacking Packetmasters

Customer Solution!

Request: aggregation and filtering traffic for monitoring system 32 x 1 Gbit links & 10 x 10 Gbit links

Layer 1 Media Conversion

The Cubro 1/10 Gbit Media converter is a nice a simple tool to solve many problems in the daily network business. You can select the media by changing the SFP. The unique design supports also CWDM / DWDM and BIDI SFP.

EX2 10 Gbit monitoring with load balanced output

Use the integrated optical TAP to connect to the live link and use the load balancing features to monitor the traffic

EX2 Multi Gbit Cooper aggregation

The Packetmaster EX2 can work as a dual link TAP with dual aggregation output, with filtering and load balancing, at the same time.