Rate and give feedback:  Feedback Received. Thank You!

Rate and give feedback: 

X

This document helped resolve my issue

Yes No

Additional Comments

800 characters remaining

May we contact you if necessary?

Name:  

E-mail: 

Enter a valid Email ID

Need product assistance? Contact Juniper Support

Submit

This site is protected by hCaptcha and its Privacy Policy and Terms of Service apply.

English  

English

Understanding QFX Series Virtual Chassis Components

Virtual Chassis Ports (VCPs)

You configure a QFX Series Virtual Chassis by configuring 10-Gbps SFP+ or 40-Gbps QSFP+ interfaces into Virtual Chassis ports (VCPs). VCPs connect switches together to form a Virtual Chassis, and are responsible for passing all data and control traffic between member switches in the Virtual Chassis. All non-channelized 40-Gbps QSFP+ interfaces on QFX3500, QFX3600, and QFX5100 series switches can be configured into VCPs; 40-Gbps QSFP+ interfaces that have been channelized into SFP+ interfaces using a breakout cable cannot be configured into VCPs. All other SFP+ interfaces on QFX series switches can be configured into VCPs, and can also be used to interconnect EX4300 switches into a mixed Virtual Chassis.

You can increase VCP bandwidth between member switches by configuring multiple interfaces between the same two switches into VCPs. When multiple VCPs are interconnecting the same two member switches, a Link Aggregation Group (LAG) bundle is automatically formed when the VCPs are on interfaces supporting identical speeds. For instance, if you have two 40-Gbps QSFP+ interfaces configured as VCPs between member switches, a LAG with two member links with 80Gbps of total bandwidth is formed. 10-Gigabit SFP+ and 40-Gbps QSFP+ interfaces configured as VCPs cannot be members of the same LAG, however. See Understanding QFX Series Virtual Chassis Port Link Aggregation

Maximum Switch Support

You can interconnect up to 10 switches into a Virtual Chassis. The Virtual Chassis can contain up to ten total member switches and the ten total member switches can include any combination of EX4300, QFX3500, QFX3600, and QFX5100 series switches.

Note: In Junos OS release 13.2X51-D20, you can interconnect up to ten QFX5100 switches into a Virtual Chassis with the exception of the QFX5100-96S switch, which you could configure into a non-mixed Virtual Chassis that included up to four QFX5100-96S switches only. You can configure up to ten QFX5100-96S switches into a mixed or non-mixed Virtual Chassis starting in Junos OS release 13.2X51-D25.

Master Role

In a Virtual Chassis, each member switch is assigned one of three roles: master, backup, or linecard.

The member that functions in the master role in the Virtual Chassis:

• Manages the member switches.
• Runs Junos OS for the switches in a master role.
• Runs the chassis management processes and control protocols.
• Represents all the member switches interconnected within the Virtual Chassis configuration. (The hostname and other properties that you assign to this switch during setup apply to all members of the Virtual Chassis configuration.)

In a Virtual Chassis, one member functions as the master and a second member functions as the backup:

• In a preprovisioned configuration, one of the two members assigned as routing-engine functions as the master member. The selection of which member assigned as routing-engine functions as master and which as backup is determined by the software based on the master election algorithm. See Understanding How the Master in a Virtual Chassis Is Elected.
• In a configuration that is not preprovisioned, the selection of the master and backup is determined by the mastership priority value and secondary factors in the master election algorithm.

All switches that are not assigned the master or backup role function in the linecard role.

In a mixed Virtual Chassis, we recommend configuring the QFX5100 switches into the master and backup role. If the mixed Virtual Chassis does not contain QFX5100 switches, we recommend configuring QFX3500 or QFX3600 switches into the master and backup roles.

Backup Role

The member that functions in the backup role in the Virtual Chassis:

• Maintains a state of readiness to take over the master role if the master fails.
• Runs Junos OS for switches in a backup role.
• Synchronizes with the master in terms of protocol states, forwarding tables, and so forth, so that it is prepared to preserve routing information and maintain network connectivity without disruption in case the master is unavailable.

You must have at least two member switches in the Virtual Chassis configuration in order to have a backup member.

• In a preprovisioned configuration, one of the two members assigned as routing-engine functions in the backup role. The selection of which member assigned as routing-engine functions as master and which as backup is determined by the software based on the master election algorithm. See Understanding How the Master in a Virtual Chassis Is Elected.
• In a configuration that is not preprovisioned, the selection of the master and backup is determined by the mastership priority value and secondary factors in the master election algorithm.

In a mixed Virtual Chassis, we recommend configuring the QFX5100 switches into the master and backup role. If the mixed Virtual Chassis does not contain QFX5100 switches, we recommend configuring QFX3500 or QFX3600 switches into the master and backup roles.

Linecard Role

A member that functions in the linecard role in the Virtual Chassis:

• Runs only a subset of Junos OS.
• Does not run the chassis control protocols.
• Can detect certain error conditions (such as an unplugged cable) on any interfaces that have been configured on it through the master.

The Virtual Chassis configuration must have at least three members in order to include a linecard member.

• In a preprovisioned configuration, you can explicitly configure a member with the linecard role, which makes it ineligible for functioning as a master or backup.
• In a configuration that is not preprovisioned, the members that are not selected as master or backup function as linecard members of the Virtual Chassis configuration. The selection of the master and backup is determined by the mastership priority value and secondary factors in the master election algorithm. A switch with a mastership priority of 0 is always in the linecard role.

Any switch can function in the linecard role in a mixed or non-mixed Virtual Chassis.

In a mixed Virtual Chassis, we recommend configuring the QFX5100 switches into the master and backup role. If the mixed Virtual Chassis does not contain QFX5100 switches, we recommend configuring QFX3500 or QFX3600 switches into the master and backup roles.

Member Switch and Member ID

Each standalone switch that supports Virtual Chassis is a potential member of a Virtual Chassis configuration. When one of those switches is powered on, it receives a member ID that can be seen by viewing the front-panel LCD or by entering the show virtual-chassis command. If the switch is powered on as a standalone switch, that member’s member ID is always 0. When the switch is interconnected with other switches in a Virtual Chassis configuration, its member ID is assigned by the master based on various factors, such as the order in which the switch was added to the Virtual Chassis configuration or the member ID assigned by a preprovisioned configuration. See Understanding How the Master in a Virtual Chassis Is Elected.

If the Virtual Chassis configuration previously included a member switch and that member was physically disconnected or removed from the Virtual Chassis configuration, its member ID is not available for assignment as part of the standard sequential assignment by the master. For example, you might have a Virtual Chassis configuration composed of member 0, member 2, and member 3, because member 1 was removed. When you add another member switch and power it on, the master assigns it as member 4.

The member ID distinguishes the member switches from one another. You use the member ID:

• To assign a mastership priority value to a member switch
• To configure interfaces for a member switch (The function is similar to that of a slot number on Juniper Networks routers.)
• To apply some operational commands to a member switch
• To display status or characteristics of a member switch

Mastership Priority

In a configuration that is not preprovisioned, you can designate the role (master, backup, or linecard) that a member switch assumes by configuring its mastership priority (from 0 through 255). The mastership priority value is the factor in the master election algorithm with the highest precedence for selecting the master of the Virtual Chassis configuration. A switch with a mastership priority of 0 never assumes the backup or master role.

The default value for mastership priority is 128. When a standalone switch is powered on, it receives the default mastership priority value. Because it is the only member of the Virtual Chassis configuration, it is also the master. When you interconnect a standalone switch to an existing Virtual Chassis configuration (which implicitly includes its own master), we recommend that you explicitly configure the mastership priority of the members that you want to function as the master and backup.

In a preprovisioned configuration, you assign the role of each member switch.