Introduction to Cisco Nexus 3232C Switch

It is undeniable that switch is the heart of the telecommunication network. Now is the time for 100G Ethernet network and 100G switch is widely deployed in data center. Cisco Unified Fabric family is able to get high-density, advanced programmability, low latency, workload isolation, and wire-rate layer 2 and 3 switching on a data-center-class, Cisco NX-OS operating system. This article is going to introduce one kind of this series—Cisco Nexus 3232C switch.

Overview of Cisco Nexus 3232C Switch

The Cisco Nexus 3232C switch is a 1U fixed form-factor 100G switch with 32 qsfp28 ports. Each QSFP28 port can operate at 10, 25, 40, 50, and 100Gbps, up to a maximum of 128 x 25Gbps ports. It runs the industry leading Cisco NX-OS Software operating system which provides customers with comprehensive features and functions that are widely deployed. In addition, the QSFP28 transceiver, AOC cable and DAC cable can work on its QSFP28 ports. Here is a figure of Cisco Nexus 3232C switch for you.

Cisco Nexus 3232C switch
Advantages of Cisco Nexus 3232C Switch

There are many advantages of Cisco Nexus 3232C switch which will be introduced in this part.

High-density ports: It structured with 32 qsfp28 ports. Each QSFP28 port can be configured to work as 4 x 25Gbps ports, offering deployment flexibility, with up to a maximum of 128 x 25Gbps ports.

Flexibility: The switch can be used for fiber-based network deployment and copper-based network deployment. Both fiber and copper cabling solutions are available for 10G, 25G, 40G, 50G and 100G connectivity, including AOC cable and DAC cable.

High performance and scalability: With a four-core CPU, 8GB of DRAM and 16Mb of dynamic buffer allocation, the switch is suitable for massively scalable data centers and big data applications.

Comprehensive programmability: It enables data center managers to run today’s applications while also preparing them for demanding and changing application needs such as big data, cloud and virtualization.

Applications of Cisco Nexus 3232C Switch

This part will introduce two 100G to 100G cabling solutions for Cisco Nexus 3232C switch to you.

Direct Connection for 100G to 100G

As the following figure shows, two 100G QSFP28 transceivers are plugged into QSFP28 ports on Cisco Nexus 3232C switch set on two sides. The two 100G QSFP28 transceivers are designed with 12-fiber MTP connector interface. Therefore, they can be directly connected by 12-fiber MTP trunk cable. This is the simplest way to achieve 100G to 100G connectivity.

direct connection for 100G to 100G
Interconnection for 100G to 100G

We can also deploy fiber enclosure to get higher density and make the cabling procedure more flexible. Since 1RU rack mount fiber enclosure is able to hold up to 4 MTP fiber adapter panels or 4 HD 12 core MTP MPO fiber optic plug-n-play cassettes, here we take MTP fiber adapter panel for example. From the figure below we can see that, the two 100G QSFP28 transceivers are plugged into QSFP28 ports on Cisco Nexus 3232C switch on two sides. The the 100G QSFP28 transceiver is connected to the MTP adaptor on MTP fiber adapter panel by 12-fiber MTP trunk cable. Then the two MTP fiber adapter panels installed inside two fiber enclosures respectively are connected by 12-fiber MTP trunk cable.

interconnection for 100G to 100G

As a compact 1RU form factor switch for top-of-rack (ToR) data center deployments, Cisco Nexus 3232C switch allows a smooth transition from 40 to 100G Ethernet infrastructure in data centers. It is a high quality 100G switch. I hope after reading this article, you can have a better understanding of Cisco Nexus 3232C switch.

Why Short Distance MTP-based Connectivity Utilizes OM3 or OM4 Fibers?

As today’s network needs to support more devices and advanced applications than ever before, the amount of data transmitted at the enterprise business level is rapidly climbing. For many data centers, 10G network no long satisfies the need of high speed data transmission. In 2010, the IEEE ratified the 40G ad 100G standard. Then how to realize smooth migration path from 10G to 40G and 100G has become the most concern for data center managers. After some comparison, many data center managers turn to MTP-based connectivity since it can provide fast installation, high density and high performance cabling for data centers. It is not difficult to find that both MTP/MPO trunk cable and MTP/MPO breakout cable (shown as the figure below) used for short distance connectivity utilize OM3 or OM4 fibers. Why short distance MTP-based connectivity utilizes OM3 or OM4 fibers? This article will show you the reason.

MTP MPO trunk cable and MTP MPO breakout cable


OM3 and OM4 fibers are the only multimode fibers included in the 40/100G standard. Multimode fibers utilize parallel optical transmission instead of serial transmission due to the 850 nm VCSEL (vertical cavity surface emitting laser) modulation limits. And OM3 and OM4 fibers have a minimum 2000 MHz∙km and 4700 MHz∙km effective modal bandwidth (EMB). The minimum EMBc (Effective Modal Bandwidth calculate) method measures the actual fiber bandwidth performance, recognizing the fact that overall system bandwidth is a function of both the bandwidth properties of the fiber and also the particle characteristics of individual laser sources, and this is the most significant factor in determining link performance. In addition, the IEEE model is the industry reference point for calculating the maximum achievable Ethernet link distance and sets out the minimum requirements of components in an optical link. Therefore, knowing the exact minimum bandwidth performance of OM3 and OM4 fibers is a prerequisite to understand the ultimate limitation of MTP-based connectivity, which can ensure the optical infrastructure deployed in the data center will meet the performance criteria set forth by IEEE for bandwidth.

Insertion Loss

No matter what kind of cabling system you are going to deploy, insertion loss is inevitable and it is an essential performance parameter of the network deployment. It is important to note that the total connectivity loss within a cabling system has an effect on the network performance over the maximum link distance at a given data transmission rate. It is not difficult to understand that the higher the total connectivity loss, the shorter the maximum link distance. As a result, the insertion loss specifications of components used for connectivity should be evaluated at first when designing data center cabling infrastructures. The 40G standard specifies that with link distance up to 100 meters, the maximum channel loss of OM3 fiber is 1.9 dB, which includes a 1.5 dB total connectivity loss budget; while for OM4 fiber, it is specified that with link distance up to 150 meters, the maximum channel loss is 1.5 dB, which includes a 1.0 dB total connectivity loss budget. And the maximum attenuation of fiber optic cable at 850 nm is 3.5 dB/km. With low-loss OM3 and OM4 fibers, maximum flexibility can be achieved with the ability to utilize MTP connector in the optical link.


With 850nm EMB of 2000 MHz∙km and 4700 MHz∙km, OM3 and OM4 fibers can provide the bandwidth which is needed in MTP-based connectivity for 40G network. Besides, low-loss within cabling system is another characteristic of OM3 and OM4 fibers, which can ensure the high performance of the network deployment. Therefore, utilizing OM3 and OM4 fibers makes short distance MTP-based connectivity an ideal solution for migration from 10G to 40G in data centers.

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In-depth Understanding of Polarity for MTP System

To meet increasing demands for high-density cabling and wider bandwidth of network applications, many data centers are migrating to the 40G and 100G Ethernet. To prepare for this change, MTP technology is applied to provide an easy migration path. Typically, a fiber optic link needs two fibers for full duplex communications. Thus the equipment on the link should be connected properly at each end. However, high-density connectivity usually requires more than two fibers in a link, which makes it more complex to maintain the correct polarity across a fiber network, especially when using multi-fiber MTP components for high data rate transmission. This article will specifically guide you to understand the polarity for MTP system and three MTP polarity methods.

What Is Polarity?

To form a fiber optic link, the optical transmitter at one end is connected to the optical receiver at the other end. This matching of the transmit signal (Tx) to the receive equipment (Rx) at both ends of the fiber optic link is referred to as polarity. In other words, polarity is the term used in the TIA-568 standard to explain how to make sure that proper connection is made between the transmitter at one end and the receiver at the other end. Once the component is connected to the wrong polarity, the transmission process will be unable to go on.

Structure of MTP Connector

As shown in the following picture, MTP connector is pin and socket connector, which requires a male side and a female side. And each MTP connector has a key on one side of the connector body. When the key sits on top, this is referred to as the key up position, and when the key sits on bottom, we call it key down position. Moreover, each of fiber holes in the connector is numbered in sequence from left to right. We will refer to these connector holes as positions, or P1, P2, etc. Besides, each connector is additionally marked with a white dot on the connector body to designate the position 1 side of the connector when it is plugged in.

Structure of MTP Connector

MTP Adapter Keying Options

MTP adapter contains an asymmetrical housing including an inverted key to achieve the appropriate fiber polarity. On type A adapters, the keys are inverted to ensure that the fiber at position 1 is connected to position 1 in the MTP fiber cable connector at the opposing end.

MTP key up to key down adapter

On type B adapters, both keys are oriented facing up in order that both MTP fiber cable connectors are mated “key up”. The fiber at position 1 is connected to position 12 in the MTP connector at the opposing end.

MTP key up to key up adapter

Three Polarity Methods for MTP System

The TIA standard defines two types of duplex fiber patch cables terminated with LC or SC connectors to complete an end-to-end fiber duplex connection: A-to-A type patch cable is a cross version and A-to-B type patch cable is a straight-through version. Based on this, there are three polarity connecting methods for MTP system. The following part will introduce them in details.

A-to-A type patch cable and A-to-B type patch cable

Method A

Method A utilizes “key up to key down” adapters to connect the MTP connectors. As the following figure shows, this method maintains registration of Fiber 1 throughout the optical circuit. Fiber 1 in the near end cassette mates to Fiber 1 in the trunk cable assembly, which mates to Fiber 1 in the remote cassette. The fiber circuit is completed by utilizing one flipped patch cord, either at the beginning or end of the permanent link, to insure proper transceiver orientation. Method A provides the simplest deployment, and works for single-mode and multimode channels, as well as can easily support network extensions.

Method A

Method B

Different from method A, method B uses “key up to key up” adapters. The fiber circuit is completed by utilizing straight patch cords at the beginning and end of the link, and all of the array connectors are mated key up to key up. This type of array mating results in an inversion, meaning that Fiber 1 is mated with Fiber 12, while Fiber 2 is mated with Fiber 11, etc. To ensure proper transceiver operation with this configuration, one of the cassettes needs to be physically inverted internally so Fiber 12 is mated with Fiber 1 at the end of the link. This method requires a more in-depth planning stage in order to properly manage the polarity of the links, and to identify where the actual inversions need to occur. Moreover, it only supports multimode fiber.

Method B

Method C

With the use of “key up to key down” adapters, method C looks like method A. However, the difference between method C and method A is that the flip does not happen in the end patch cords, but in the array cable itself. This method requires a more in-depth planning stage in order to properly manage the polarity of the links, and to identify where the actual flipped array cord is placed in the link. An additional drawback to this method is that if this link was to be extended, a straight array cord as used in Method A would need to be used to revert the polarity back to straight array polarity condition. In other words, unflip the array cable.

Method C


Knowing the polarity of MTP system helps you better upgrade the 40G and 100G networks. According to different polarity methods, choosing the right MTP patch cables, MTP connectors and MTP cassettes will provide greater flexibility and reliability for your high-density network.