Configuring Mixed-mode Virtual-Chassis with Juniper EX-series Switches

Recently I was building a Virtual-chassis with Juniper EX-series Switches. I’m now sharing my experience.

Virtual-chassis combines EX-series switches together as a one logical device. Basically, one control-plane (or Routing-Engine) and multiple data-planes (or Packet Forwarding Engines) are active concurrently.

In a basic virtual-chassis, multiple EX4200, EX4500 or EX4550 series switches are combined together. Mixed-mode Virtual-Chassis can have all of them in one single virtual-chassis.

I followed Juniper documentation and tried to create virtual-chassis. Step number 8 was a little bit unclear:

8. (Mixed Virtual Chassis with EX4200 switches only) Set the Virtual Chassis mode to mixed on all member switches if your mixed Virtual Chassis includes EX4200 switches:

user@switch> request virtual-chassis mode mixed
On which switches would you configure the command above, based on the instructions? When I first read this, I thought you should configure this only to EX4200 series switches. I did it, and all switches went to linecard role. After couple of reboots, I read step number 8 again. First it says, “EX4200 switches only” and then “on all member switches”. After couple of minutes thinking and conversation with colleagues, I realized what that really means:
1) If you have a Mixed-mode Virtual-chassis which includes an EX4200, run the command on all switches.
2) If you have a Mixed-mode Virtual-chassis without an EX4200 (that is only EX4500 and EX4550 switches), then you don’t need this command on any switch. This is mainly because the EX4500 and EX4550 have almost identical hardware.
For me, it seems that the instructions make sense, but should have a little bit longer of an explanation to improve clarity.
P.S. Bonus tip: request virtual-chassis renumber command saves you lots of your time if the virtual-chassis member numbers went wrong.


  1. Allen Baylis says

    Common error but the key word is mixed -mode. Juniper’s EX switches are pretty straight forward and virtually no problems . The EX45004550 are designed to support Virtual Chassis up to 10 interconnected switches to operate as a single,logical device supporting up to 480 10Gb. Its connected over a 128 Gbps backplane compatible with the EX4200 line of Ethernet switches.

    The command request virtual-chassis renumber wasn’t always an option until later releases of JUNOS but yes a handy command to re-organize the numbering scheme.

    Allen Baylis

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