MLAG – Advanced Configuration


While dual-homing individual devices such as servers and top of rack switches using MLAG provides fault-tolerant, active-active connectivity across a single device pair, larger networks require two tier architectures to provide fully meshed capacity both between the spine and leaf layers of the network and for onward connection to servers. MLAG’s simple yet versatile implementation makes it possible to provide high levels of redundancy with scalability of up to 64 interfaces per channel between multiple pairs of devices enabling significant network expansion without resorting to Spanning Tree.



MLAG – basic configuration

MLAG overview

LAG or link aggregation is a way of bonding multiple physical links into a combined logical link. MLAG or multi-chassis link aggregation extends this capability allowing a downstream switch or host to connect to two switches configured as an MLAG domain. This provides redundancy by giving the downstream switch or host two uplink paths as well as full bandwidth utilization since the MLAG domain appears to be a single switch to Spanning Tree (STP). Because the MLAG domain appears to STP as a single switch there are no blocked ports.



What’s the difference between PEM and PS?

Correct Answer by Shashank Singh about 6 years 3 months ago

There is no real difference. PEM and PS are the modules that supply power to the switch/router. In some cases they also perform the AC to DC conversion as required by some platforms.

For example, PEM was replaced by PS after it became EOL in case of 7600 routers.

End-of-Sale Product Part Number


Power Entry Module for CISCO7606 (1900W Pwr Sup)

Replacement Product Part Number


2700W AC power supply for CISCO7606

In case of some routers (10k series), the power unit is still called PEM.



P.S. Please rate helpful posts.



Day One Library

Day One Library

The Day One library gives you just the information you need to complete a networking task in your lab and then take it out into production. The Day One series covers the Junos OS and Juniper networking essentials with straightforward explanations, step-by-step instructions, and practical examples that are easy to follow. Over 750K downloads and growing.

The Day One Library is available as free PDFs by clicking the links below. You will be taken to J-Net, Juniper’s User Community.

If you are not a member, you will be asked to join and provide an email address and a password (it’s a Juniper community). Then, in the future, you’ll receive an occasional email notifying you of new books added to the library.

Networking Fundamentals

Exploring the Junos CLI, Second Edition
Data Center Fundamentals
Routing the Internet Protocol
Hardening Junos Devices, Second Edition
Finishing Junos Deployments
Deploying Basic QoS
Junos Tips, Techniques, and Templates 2011
MPLS for Enterprise Engineers
Exploring IPv6


Enabling Automated Network Verifications with JSNAPy
Using JSNAP to Automate Network Verifications
Junos Automation Reference for SLAX 1.0
Mastering Junos Automation
Applying Junos Automation
Navigating The Junos XML Hierarchy
Dynamic Subscriber Management


Deploying BGP FlowSpec


Migrate Cisco ASA to Juniper SRX Series
Junos QoS for IOS Engineers
Junos for IOS Engineers
Migrating EIGRP to OSPF


CGNAT Up and Running on the MX Series
Packet Walkthrough on the MX Series 3D
Deploying MPLS
Configuring Junos Policies and Firewall Filters
Exploring IPv6
Monitoring and Troubleshooting
SBR Change of Authorization (CoA) and the MX Series
Walkthrough on the M, MX, and T Series
Advanced IPv6 Configuration


Deploying Zero Touch Provisioning
Configuring EX Series Ethernet Switches, Third Edition


NorthStar Controller Up and Running
Understanding OpenContrail Architecture
vMX Up and Running


ADVPN Design and Implementation
Deploying BGP Multicast VPNs, Second Edition
Using Ethernet VPNs for Data Center Interconnect


Juniper Ambassadors’ Cookbook 2017
Juniper Ambassadors’ Cookbook for 2014
Juniper Ambassadors’ Cookbook for Enterprise
Advanced Junos CoS Troubleshooting Cookbook