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Juniper MX Series by Harry Reynolds, Douglas Richard Hanks Jr.

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Chapter 1. Juniper MX Architecture

Back in 1998, Juniper Networks released its first router, the M40. Leveraging Application Specific Integrated Circuits (ASICs), the M40 was able to outperform any other router architecture. The M40 was also the first router to have a true separation of the control and data planes, and the M Series was born. Originally, the model name M40 referred to its ability to process 40 million packets per second (Mpps). As the product portfolio expanded, the “M” now refers to the multiple services available on the router, such as MPLS with a wide variety of VPNs. The primary use case for the M Series was to allow Service Providers to deliver services based on IP while at the same time supporting legacy frame relay and ATM networks.

Fast forward 10 years and the number of customers that Service Providers have to support has increased exponentially. Frame relay and ATM have been decimated, as customers are demanding high-speed Layer 2 and Layer 3 Ethernet-based services. Large enterprise companies are becoming more Service Provider-like and are offering IP services to departments and subsidiaries.

Nearly all networking equipment connects via Ethernet. It’s one of the most well understood and deployed networking technologies used today. Companies have challenging requirements to reduce operating costs and at the same time provide more services. Ethernet enables the simplification in network operations, administration, and maintenance.

The MX Series was introduced in 2007 to solve these new challenges. It is optimized for delivering high-density and high-speed Layer 2 and Layer 3 Ethernet services. The “M” still refers to the multiple services heritage, while the “X” refers to the new switching capability and focus on 10G interfaces and beyond; it’s also interesting to note that the Roman numeral for the number 10 is “X.”

It’s no easy task to create a platform that’s able to solve these new challenges. The MX Series has a strong pedigree: although mechanically different, it leverages technology from both the M and T Series for chassis management, switching fabric, and the routing engine.

Features that you have come to know and love on the M and T Series are certainly present on the MX Series as it runs on the same image of Junos. In addition to the “oldies, but goodies,” is an entire featureset focused on Service Provider switching and broadband network gateway (BNG). Here’s just a sample of what is available on the MX:

High availability

Non-Stop Routing (NSR), Non-Stop Bridging (NSB), Graceful Routing Engine Switch over (GRES), Graceful Restart (GR), and In-Service Software Upgrade (ISSU)


RIP, OSPF, IS-IS, BGP, and Multicast


Full suite of Spanning Tree Protocols (STP), Service Provider VLAN tag manipulation, QinQ, and the ability to scale beyond 4,094 bridge domains by leveraging virtual switches

Inline services

Network Address Translation (NAT), IP Flow Information Export (IPFIX), Tunnel Services, and Port Mirroring



Broadband services

PPPoX, DHCP, Hierarchical QoS, and IP address tracking


Multi-Chassis Link Aggregation, Virtual Chassis, Logical Systems, Virtual Switches

With such a large featureset, the use case of the MX Series is very broad. It’s common to see it in the core of a Service Provider network, providing BNG, or in the Enterprise providing edge routing or core switching.

This chapter introduces the MX platform, features, and architecture. We’ll review the hardware, components, and redundancy in detail.

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