An Overview on EVPN and LNV

Bombarded with assorted network applications and protocols, the technologies and solutions for network virtualization delivery have been enriched greatly over past years. Among those technologies, VXLAN, also called virtual extensible local area network, is the key network virtualization. It enables layer 2 segments to be extended over an IP core (the underlay). The initial definition of VXLAN (RFC 7348) only relied on a flood-and-learn approach for MAC address learning. Now, a controller or a technology such as EVPN and LNV in Cumulus Linux can be realized. In this post, we are going to make an exploration on those two techniques: LNV and EVPN.


Figure 1: VXLAN

What Is EVPN

EVPN is also named as Ethernet VPN. It is largely considered as a unified control plane solution for the controller-less VXLAN, allowing for building and deploying VXLANs at scale. The EVPN relies on multi-protocol BGP (MP-BGP) to transport both layer 2 MAC and layer 3 IP information at the same time. It enables a separation between the data layer and control plane layer. By having the combined set of MAC and IP information available for forwarding decisions, optimized routing and switching within a network becomes feasible and the need for flooding to do learning gets minimized or even eliminated.

What Is LNV

LNV is the short of lightweight network virtualization. It is a technique for deploying VXLANs without a central controller on bare metal switches. Typically, it’s able to run the VXLAN service and registration daemons on Cumulus Linux itself. The data path between bridge entities is established on the top of a layer 3 fabric by means of a simple service node coupled with traditional MAC address learning.

The Relationship Between EVPN and LNV

From the above wiki of the EVPN and LNV, it’s easy for us to notice these two technologies are both the applications of VXLAN. For LNV, it can be used to deploy VXLAN without an external controller or software suite on the bare-metal layer 2/3 switches running Cumulus Linux network operating system (NOS). As for EVPN, it is a standards-based control plane for VXLAN, which can be used in any usual bare-metal devices, such as network switch and router. Typically, you cannot apply LNV and EVPN at the same time.

Apart from that, the deployments for EVPN and LNV are also different. Here, we make a configuring model for each of them for your better visualization.

EVPN Configuration Case



Figure 2: EVPN

In the EVPN-VXLAN network segments shown in Figure 2 (Before), hosts A and B need to exchange traffic. When host A sends a packet to host B or vice versa, the packet must traverse the switch A, a VXLAN tunnel, and the switch B. By default, routing traffic between a VXLAN and a Layer 3 logical interface is disabled. If the functionality is disabled, the pure Layer 3 logical interface on the switch A drops Layer 3 traffic from host A and VXLAN-encapsulated traffic from the switch B. To prevent the pure Layer 3 logical interface on the switch A from dropping this traffic, you can reconfigure the pure Layer 3 logical interface as a Layer 2 logical interface, like Figure 2 (After). After that, you need to associate this interface with a dummy VLAN and a dummy VXLAN network identifier (VNI). Then, an Integrated routing and bridging (IRB) interface need to be created, which provides Layer 3 functionality within the dummy VLAN.

LNV Configuration Case



Figure 3: LNV

The two layer 3 switches are regarded as leaf 1 and leaf 2 in the above figure. They are running with Cumulus Linux and have been configured as bridges. Containing physical switch port interfaces, the two bridges connect to the servers as well as the logical VXLAN interface associated with the bridge. After creating a logical VXLAN interface on both leaf switches, the switches become VTEPs (virtual tunnel end points). The IP address associated with this VTEP is most commonly configured as its loopback address. In the image above, the loopback address is for leaf 1 and for leaf 2.


In this post, we have introduced the two techniques of network virtualization: EVPN and LNV. These two applications of network virtualization delivery share some similarities, but also quite a lot of differences. Being satisfied with the simplicity, agility, and scalability over the network, the EVPN has been a popular choice in the market.

MTP Solutions for High-Density Needs

With the ever-increasing demands for high-density backbone cabling. MTP solutions have enjoyed widespread popularity. In this post, we will have an exploration of two MTP solutions: MTP cable and MTP cassette. For those who are unfamiliar with this term, it’s necessary for us to get started from its basics.

Background Information on MTP

In this part, you are required to acquire three terms: MTP, MPO, and polarity.


MPO stands for “multi-fiber push on” connector. Usually, it refers to a type of a multiple fiber core connector, defined by IEC-61754-7 (common standard) and the U.S. TIA-604-5 Standard.


MTP is the short for “multi-fiber termination push-on” connector, which is the latest generation of MPO connector developed by US Conec. Fully compliant with the MPO standards, the multi-fiber termination push-on connector is considered as MPO fiber connector. For multi-fiber termination push-on or multi-fiber push on connector, they can both accommodate 8 to 24 fibers, which are the perfect choices for the 40G/100G network. Multi-fiber termination push-on or multi-fiber push on connector is available in a female version (without pins), or a male version (with pins) as shown in figure 1. The pins ensure the exact alignment of the fronts of the connectors, which protects the interfaces of the connectors from being offset.

MTP Connectors

Figure 1: MTP Connectors

Also, there are guide grooves (keys) on the top side of the factory terminated multi-fiber termination push-on connectors, which ensure that the adapter holds the connector with the correct ends aligned with each other. According to the key, the multi-fiber termination push-on connector comes with two types. One is “key-up to key-down”, which means the key is up on the one side and down on the other. The two connectors are connected turned 180°in relation to each other. The other one is “key-up to key-up”, which means both keys are up. The two connectors are connected while in the same position in relation to each other.

MTP Connector Structure

Figure 2:  Multi-fiber Termination Push-on Connector Structure


In any installation, it is important to ensure that the optical transmitter at one end is connected to the optical receiver at the other. This matching of the transmitting signal (Tx) to the receiving equipment (Rx) at both ends of the fiber optic link is referred to as polarity.

MTP Solutions

For multi-fiber termination push-on solutions, there are two frequently used applications: MTP cable and multi-fiber termination push-on cassettes. They are the best choices for providing a simple, cost-effective, and structured cabling system.

MTP Solutions

Figure 3: MTP Solutions


Multi-fiber termination push-on cables usually consist of the multi-fiber termination push-on connectors and the fiber optic cables. Sometimes, the LC connectors are used, which we will expound in the following part. As for fiber cables, they are typically used in OS2, OM3 or OM4. With different applications, the multi-fiber termination push-on cable can be classified into multi-fiber termination push-on trunk cable and multi-fiber termination push-on harness cable.

Trunk Cable

Serving as a permanent link, the trunk cable is designed to connect multi-fiber termination push-on or multi-fiber push on modules to each other. It’s available in 12, 24, 48 and 72 fibers. For the ends, the cable is commonly found to be terminated with 12-fiber or 24-fiber multi-fiber termination push-on or multi-fiber push on connectors. When it comes with the polarity of the patch cord, there are three different types (type A, B, and C), which is defined in the TIA standard. In the following figures, the three different connectivity methods for 12-fiber and 24-fiber MTP/MPO trunk cable are showed respectively.

12-Fiber MTP Trunk Cable

Figure 4: 12-Fiber Multi-fiber Termination Push-on Trunk Cable

24-Fiber MTP Trunk Cable

Figure 5: 24-Fiber Multi-fiber Termination Push-on Trunk Cable

Harness Cable

Multi-fiber termination push-on harness cable is used to provide a transition from multifiber cables to individual fibers or duplex connectors. For instance, 8 fibers 12 strands MTP-LC breakout cable has eight LC fiber connectors and a multi-fiber termination push-on connector. According to data of FS.COM, the 8-fiber and 24-fiber MTP to LC breakout cables are the best-selling multi-fiber termination push-on connector harness cables. For the polarity, the 8-fiber multi-fiber termination push-on connector breakout patch cord has two types (Type A and Type B); while the 24-fiber harness cable has three types (Type A, Type B, and Type C). For details, please refer to the following figures.

12-Fiber MTP Harness Cable

Figure 6: 12-Fiber Multi-fiber Termination Push-on Harness Cable

24-Fiber MTP Harness Cable

Figure 7: 24-Fiber Multi-fiber Termination Push-on Harness Cable


MTP-cassette is a kind of pre-terminated cassette module. It enables the “transition” from ribbon cables terminated with multi-fiber termination push-on connector connectors to the LC or SC interface on the transceiver terminal equipment. Conventionally, the multi-fiber termination push-on connector cassette is loaded with 8, 12 or 24 fibers and have LC or SC adapters on the front side and multi-fiber termination push-on connector at the rear. Nowadays, the three most widely used cassettes are MTP-8, MTP-12, and MTP-24 cassettes, or also known as Base-8, Base-12, and Base-24 multi-fiber termination push-on cassettes. For MTP-8 cassette, it is only available in Type A. While multi-fiber termination push-on-12 and multi-fiber termination push-on-24 cassettes both come with Type A and Type AF. For their polarity details, please refer to the following figures.

MTP-8 Cassette

Figure 8: Multi-fiber Termination Push-on-8 Cassette

MTP-12 Cassette

Figure 9:  Multi-fiber Termination Push-on-12 Cassette

MTP-24 Cassette

Figure 10:  Multi-fiber Termination Push-on-24 Cassette


In this post, we make an overview of MTP, including what the multi-fiber termination push-on and multi-fiber push on, and what their the polarities are. Then we share three types of multi-fiber termination push-on solutions for high-density networking: MTP trunk cable, MTP harness cable, and MTP cassette.

What Cable Should I Use for My 10G Transceiver Module?

To deploy the optical network, the transceiver module and patch cable are the two basic components. According to the feedbacks of customers from FS.COM, one of the common problems faced by them is what cables they should use for their transceiver modules. To solve this problem, we make this post of patch cable selection guidance. Since the order for 10G transceivers ranks top, we are going to take 10G modules as a reference.

An overview of 10G Transceiver Module

Transceiver module, also called fiber optic transceiver, is a hot-pluggable device that can both transmit and receive data. By combining a transmitter and receiver into a single module, the device converts electrical signals into optical signals to allow these signals to be efficiently transferred on fiber optic cables. As for the 10G transceiver, it refers to the optical modules with 10G data rate. In FS.COM, there are mainly four types of 10G transceivers: XENPAK, X2, XFP, and SFP+. Even though these optical transceivers are all accessible to the 10G networks, they have different matching patch cables and applications.

10G Transceiver Module

Figure 1: 10G Transceiver Modules

Patch Cable Basics

Apart from optical module, the patch cable is the other vital role in networking. Patch cable, also called patch cord, refers to the copper or optical cable. It’s designed to connect one electronic or optical device to another for signal routing. Conventionally, the patch cable will be terminated with connectors at both ends. For example, the LC fiber cable refers to the optical cable fixed with LC connector. Typically, there are LC, SC, ST, FC and MTP/MPO fiber patch cables. According to different features, we can get various classifications of patch cables, such as fiber types, polishing types, etc.

Patch Cables

Figure 2: Patch Cables

Factors to Consider When Choosing Patch Cable for 10G Transceiver Module

Recently, most of the 10G transceiver modules are compatible with different brands and support higher data rates. It will be much easier to choose optical modules for your networking than selecting mating patch cables. Based on most applications, there are three major factors that can be taken into consideration: transmission media, transmission distance, and transceiver module interface.

Transmission Media

Classified by transmission media, two types of patch cables can be found in the market: optic fiber cable and copper cable. Correspondingly, there are two kinds of optical transceivers available: copper-based transceivers and fiber optic based transceivers. Copper transceiver modules like 10GBASE-T SFP+, they have an RJ45 interface, connecting with copper cables. Typically, Ethernet cables that support 10G copper-based transceivers are Cat7 and Cat6a cables.

As for the 10G optical modules, they can support higher data rates over optic fiber cables. It will be more complicated to choose fiber cables. Generally, there are multimode fibers and single mode fibers. Based on the specified needs for transmission distance, the answer will be varied.

Transmission Distance

To select cables, transmission distance is also an important factor that you need to take care. In the following table, we list the basic information of common 10G transceivers, including their supporting fiber cable types and transmitting distance.

Transceiver Type
Cable Type
Transmission Distance
850 nm
300 m
1310 nm
10 km
1550 nm
40 km
1550 nm
80 km

As for fiber cables, single mode fiber is used for long-distance transmission and multimode fiber is for short distance. In a 10G network, the transmission distance of single mode fiber (OS2) can reach from 2 km to 100 km. When it comes to multimode fibers, the transmission distances for OM1, OM2, OM3 are 36 m, 86 m and 300 m. OM4 and OM5 can reach up to 550 m.

Transceiver Module Interface

Another factor you need to consider is the transceiver interface. Usually, transceivers use one port for transmitting and the other port for receiving. They tend to employ duplex SC or LC interface. However, for 10G BiDi transceivers, it only has one port for both transmitting and receiving. Simplex patch cord is applied to connect the 10G BiDi transceiver.


For your 10G network cabling, transceiver module and patch cable are necessary components. With a wide range of patch cables, selecting the right patch cables will be more complex than 10G transceivers. Generally, three major factors can be considered: transmission media, transmission distance, and transceiver module interface. To apply what you have learned in this post in cabling, you can visit FS.COM for all the transceivers and patch cables at one shop.

How to Troubleshoot Transceiver and Switch Port Through Loopback Test?


Loopback is a commonly used term in telecommunications. It refers to the process of transmitting electronic signals or digital data streams and returning to their sending point without any intentional processing or modification. Therefore, by comparing transmitting signals with the receiving signals, the loopback test is used to debug physical connection problems. But what a loopback test means for fiber optic network and how to make use of it will be the issues that we will explore in this post.

Why Need Fiber Loopback Test?

To conduct a fiber loopback test, the communication devices will be involved, like the transceivers and the switch. As you know, the transceiver is the basic component of fiber optic communication network equipment. We can take the transceiver as a case. Conventionally, a transceiver has a transmitting port and a receiving port, in that way, the loopback test can be applied to test the ports to diagnose whether the transceiver is working well and the configuration of the switch is right. For its unique working mode, the test is a convenient way to maintain transceivers. In the next part, we will deliver how to do the fiber loopback test on the transceiver.

How to Conduct Loopback Test?

In this part, we will introduce two types of tests to troubleshoot transceiver and switch port: single-port test and dual-port test.

Tools You Need to Prepare

To perform tests, things you need to prepare are listed below:

  • Transceivers (2pcs), such as 10G SFP+ SR transceiver.
  • Simplex fiber cable (1 pc).
  • Switch (1 pc), like Cisco switch.
  • Duplex fiber cable (1 pc).
  • Two loopback cables (optional), like LC or SC loopback cable. To know more about loopback cable, you can move to the article: What Is Loopback Cable And How to Use It?
Loopback Cable

Figure 1: Loopback Cable

Loopback Test Steps
Single-port Loopback Test
Single-port Loopback Test

Figure 2: Single-port Loopback Test

1. Connect your transceiver with one simplex fiber cable or loopback cable, such as LC fiber cable or LC loopback cable. At this step, you can examine whether the port and transceiver parameters are normal.

2. Check the software version of the switch.

3. Review the interfaces status to confirm the working status of all ports on the switch.

Display the Working Status of All Ports

Figure 3: Display the Working Status of All Ports

4. Check the working status of the port you are connecting, such as the port 50 in the following figure.

Working Status of Interface 50

Figure 4: Working Status of Interface 50

5. Go over the DDM information to review whether the transceiver works in normal status.

DDM Information of Port 50

Figure 5: DDM Information of Port 50

Dual-port Loopback Test
Dual-port Loopback Test

Figure 6: Dual-port Loopback Test

1. Connect two transceivers with one duplex fiber cable or two loopback cables. At this step, you can examine whether the port and transceiver data rate are matching as well as the link is normal or not.

2. Check the interfaces status to confirm the working status of all ports on the switch.

Ports Working Status Display

Figure 7: Ports Working Status Display

3. Check the working status of the two ports you are connecting, such as the ports 50 and 52 in the following figure.

Working Status of Interfaces 50 and 52

Figure 8: Working Status of Interfaces 50 and 52

4. Go over the DDM information to review whether the transceiver works in normal status.

DDM Information of Ports 50 and 52

Figure 9: DDM Information of Ports 50 and 52


To troubleshoot the circuit connectivity as well as the transceiver and the switch port, loopback test is a cost-effective way. In this post, we have an overview of loopback and make a demonstration of how to conduct the loopback test on a switch to debug the transceiver and the switch port.

FMT 4000E for DWDM Network Solution

In the network era, the demand for greater traffic capacity, higher bandwidth, and better performance over longer transmission distance have never stopped. Under such a context, the optic transport network (OTN) has undergone great changes to survive. At the moment, FS provides their all-in-one dense wavelength division multiplexing (DWDM) OTN solutions. In this post, we will share one of the most popular DWDM solutions: FMT 4000E.

DWDM Network Basics


Dense wavelength division multiplexing is a technology based on wavelength-division multiplexing (WDM). It combines or multiplexes data signals from different sources for transmissions over a single fiber optic cable. At the same time, data streams are completely separated. Each signal is carried on a separate light wavelength. In most cases, the dense wavelength division multiplexing technology is applied in metropolitan network.

Optical Transport Network

Defined by the ITU Telecommunication Standardization Sector (ITU-T), OTN is a set of optical network elements (ONE) that are connected by optical fiber links. Sometimes, it’s also called the digital wrapper technology which provides an efficient and globally accepted way to multiplex different services onto optical light paths. This technology provides support for optical networking by using WDM unlike its predecessor SONET/SDH. It’s able to create a transparent, hierarchical network designed for use on both WDM and time division multiplexing (TDM) devices. The OTN is able to support functions, like transport, multiplexing, switching, management, supervision, and builds OTN client (e.g. SONET/SDH, IP, ATM) connections in the Metro and Core networks.

Optical Transport Network

Figure 1: Optical Transport Network

DWDM Network

The DWDM based network refers to a kind of dense wavelength division multiplexing technology based OTN solution. Compared with CWDM, the DWDM uses more sophisticated electronics and photonics, which makes its transmitting channel are narrower than CWDM channels. Therefore, for a DWDM network, it can support more channels and separate wavelengths (up to 80 wavelengths). It can transmit data in IP, ATM, SONET, SDH, and Ethernet. For it’s protocol and bitrate independent, the DWDM-based OTN networks can carry different types of traffic at different speeds over an optical channel.

DWDM vs CWDM Wavelength

Figure 2: DWDM vs CWDM Wavelength

FMT 4000E for DWDM Solution

In order to make the DWDM OTN deployment easier, FS has launched the high integration FMTWDM transport networks, such as FMT 1800 and FMT 9600E. In this post, we will mainly introduce the most popular solution: FMT 4000E.

What Is FMT 4000E

The FMT 4000E is a device that combines the OTN switching and dense wavelength division multiplexing features and provides unified transmission of all services. It integrates DWDM equipment with OTN function cards (EDFA, DCM, OEO) in a 4U form factor. With FMT 4000E, you can extend the optical link power budget for building long-distance dense wavelength division multiplexing solutions.

FMS 4000E

Figure 3: FMT 4000E

Strengths of FMT 4000E
  • Supports up to 40 wavelengths via the dual fiber bi-directional transmission mode.
  • Transmits up to 100 km with DWDM SFP+ 80km at the rate of 10Gbps.
  • Optional function cards to meet various needs (WDM Mux/Demux, EDFA, DCM, OEO).
  • Dual AC or DC pluggable power supply and fan unit.
  • Supports SDH/SONET, PDH, Ethernet, SAN, LAN, video service transport.
  • Scales easily for the ring, end to end and mesh networks.
  • Suitable for the enterprise, medical, Storage Area Networks (SANs), data centers, campus optical network and video surveillance.
  • Scalable solution for customers to expand capacity as needed. And operating costs and vital resources are greatly saved.
  • Ensure the maximum bandwidth for the required capacity and transmission distances.
  • Fully managed, configured and monitored remotely via FS.COM intelligent network management unit.
  • Simple installation, operation, and maintenance.
  • Standards-based and can integrate with third-party solutions.
  • The solution can be customized to suit specified customer application requirements.
Solution Topology
FMS 4000E Solution Topology

Figure 4: FMT 4000E Solution Topology

Note: This solution does not come with OPM, OPD, OLP, OSW card.

Matching Products
  • 40CH C21-C60 DWDM Mux Card ( 2pcs)
  • 40CH C21-C60 DWDM Demux Card ( 2pcs)
  • 20dB Gain Pre-Amplifier DWDM EDFA Card (2pcs)
  • 17dB Output Booster EDFA Card (2pcs)
  • 40km Passive Dispersion Compensation Card (4pcs)
  • FMT 4U Managed Chassis (2pcs)
  • LC/UPC Single Mode Fixed Fiber Optic Attenuator, 3dB (1pc)


Obsessed with higher bandwidth applications and the simplest operation, the OTN has broken through its traditional operation and make inroads into the highly integrated OTN. Undoubtedly, the DWDM solution will be the one having the last laugh after networking ups and downs. To share that last laugh, FS provides its DWDM solutions for multi-service optical transport over ultra-long distance: FS WDM Multi-service Transport (FMT) series. They help our customers to build an access transport network with more flexible service access, easier operation, and lower OPEX.