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Using a Breakout Cable with a Breakout TAP

Posted by Jonathan Devoy | 9/25/18 8:00 AM
A term that is often used when discussing the advantages of using an aggregation appliance is "Speed Conversion." Speed conversion enables communication between Multimode 40Gb or 100Gb connections, using MTP/MPO connectors, and with 10Gb or 25Gb connections using LC connectors. This mismatch of connection media is bridged through the use of a breakout cable.

A breakout cable will have an MTP/MPO connector on the end that terminates into a 40/100G QSFP+ transceiver and eight (8) simplex LC (or four (4) duplex LC) connectors on the side terminating into the 10/25G SFP+ transceiver. When using a breakout cable with a TAP and an Aggregator, it is important to ensure you are connecting the correct cables to the correct ports.

The 40G QSFP+ ports on the Advanced Aggregators can be broken out into four 10Gb connections using MTP to 8LC breakout cables. These cables separate out the eight lanes of traffic into individual connections:

MTP Breakout cable Diagram

On the breakout cable, the connectors should be labeled 1 through 4 and 9 through 12. Connectors 1 through 4 are connected to the lanes on the QSFP that are Transmitting data. These connectors should be connected into the receive port on a SFP+ transceiver. Connectors 9 through 12 are connected to the lanes on the QSFP that are Receiving data. These connectors should be connected into the transmit port on a SFP+ transceiver.

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The lanes on the QSFP correspond to each other: 1 & 12, 2 & 11, 3 & 10, and 4 & 9. These connectors need to be kept together when connecting to SFP+ transceivers for the QSFP to keep the correct traffic together.

When connecting the breakout cable to a Passive Fiber Breakout TAP, the monitor ports work differently than connecting to a SFP+ transceiver:


MTP breakout cable with Breakout TAP
The LC monitor ports on a breakout TAP are both transmitting data, so the Transmit connectors on the breakout cable will not be used. Only connectors 9, 10, 11, and 12 will be used. When connecting a breakout cable to a Passive Fiber Breakout TAP, each QSFP port will be able to support two 10Gb breakout TAPs.

Topics: Network TAPs

Written by Jonathan Devoy

Jonathan is a System Engineer for Garland Technology in the Buffalo, New York office, providing solution designs and support for all levels of the sales cycle. Jonathan's previous experience consists of networking pre-sales support for both Juniper and Citrix.