Discover Juniper Network's virtual chassis technology. Get hands-on with the solution using EX4200 and 3300 switches!
Real-world use case
You want to pool two Juniper switches into a single logical device: discover how to configure a virtual chassis under Junos.
Juniper Network's virtual chassis technology:
Virtual chassis technology lets you interconnect devices and manage them as a single logical device. The control plane (JunOS) distributes the same information to all the other switches. So the logical entity called Virtual chassis has the same information "as if it were a single physical entity" (source: SILICON.FR).
More information about Juniper's virtual chassis at the following address: understanding the virtual chassis.
Hardware prerequisites:
We're going to configure two chassis; in my case I have the following physical hardware available:
To create an EX4200 virtual chassis
- Three dedicated VCP cables (to connect the EX4200 switches).
- One switch: EX4200-24px.
- Two switches: EX4200-24t.
To create an EX3300 virtual chassis
- One 1m SFP+ DAC cable (to connect the two EX3300s).
- One switch: EX3300-24p.
- A second switch: EX3300-48px.
In this case, we have two different interconnection scenarios for our virtual chassis:
- Connection via dedicated cables (VCPs).
- Connection via the front-panel SFP+ ports.
The cabling method and virtual chassis configuration
Virtual chassis with 3x EX4200 (master/backup/linecard)
On the back of the switch panels (SW0/SW1/SW2), you have two VCP ports: 0 and 1, and we'll connect them to each other:
- SW0 port vcp 0 to port vcp 1 on SW1.
- SW0 port vcp 1 to port vcp 0 on SW2.
- SW1 port vcp 0 to port vcp 1 on SW2.
Each switch is connected to the next one, while the first and last form a loop.
Let's now display our virtual-chassis configuration in JunOS:
show virtual-chassis vc-port
fpc0:
--------------------------------------------------------------------------
Interface Type Trunk Status Speed Neighbor
or ID (mbps) ID Interface
PIC / Port
vcp-0 Dedicated 2 Up 32000 1 vcp-1
vcp-1 Dedicated 1 Up 32000 2 vcp-0
fpc1:
--------------------------------------------------------------------------
Interface Type Trunk Status Speed Neighbor
or ID (mbps) ID Interface
PIC / Port
vcp-0 Dedicated 2 Up 32000 2 vcp-1
vcp-1 Dedicated 1 Up 32000 0 vcp-0
fpc2:
--------------------------------------------------------------------------
Interface Type Trunk Status Speed Neighbor
or ID (mbps) ID Interface
PIC / Port
vcp-0 Dedicated 2 Up 32000 0 vcp-1
vcp-1 Dedicated 1 Up 32000 1 vcp-0
For a better understanding of the result, head to: show virtual chassis vcp port, and for a master/backup-only configuration, refer to the following article: EX4200 (master/backup).
You'll find other examples here: virtual chassis cabling example (EX4200).
Virtual chassis with 2x EX3300 (master/backup)
On the front of each switch's panel, we'll use the SFP+ DAC cable, note that the ports will then be named XE-0/1/0 through 0/3/0. Note that ports 2 and 3 are configured in the VCP by default on EX3300s.
Additional information: virtual chassis EX3300.
To make sure this is the case:
show virtual-chassis vc-port
fpc0:
--------------------------------------------------------------------------
Interface Type Trunk Status Speed Neighbor
or ID (mbps) ID Interface
PIC / Port
1/2 Configured -1 Up 10000 1 vcp-255/1/2
1/3 Configured Absent
fpc1:
--------------------------------------------------------------------------
Interface Type Trunk Status Speed Neighbor
or ID (mbps) ID Interface
PIC / Port
1/2 Configured -1 Up 10000 0 vcp-255/1/2
1/3 Configured Absent
As a practical example, we want to drop ports 2 and 3 and only use port 1. Here's how to proceed:
- Delete the existing vc-port configuration locally:sql
request virtual-chassis vc-port delete pic-slot 1 port 2 request virtual-chassis vc-port delete pic-slot 1 port 3 - Delete the existing vc-port configuration on member 1 (second switch):sql
request virtual-chassis vc-port delete pic-slot 1 port 2 member 1 request virtual-chassis vc-port delete pic-slot 1 port 3 member 1 - Add our vc-port configuration on port 0 locally:bash
request virtual-chassis vc-port set pic-slot 1 port 0 - Add our vc-port configuration on port 0 on member 1 (second switch):bash
request virtual-chassis vc-port set pic-slot 1 port 0 member 1 - Verifying our virtual chassis:bash
show virtual-chassis vc-port fpc0: -------------------------------------------------------------------------- Interface Type Trunk Status Speed Neighbor or ID (mbps) ID Interface PIC / Port 1/0 Configured -1 Up 10000 1 vcp-255/1/0 fpc1: -------------------------------------------------------------------------- Interface Type Trunk Status Speed Neighbor or ID (mbps) ID Interface PIC / Port 1/0 Configured -1 Up 10000 0 vcp-255/1/0
Roles and switch organization within a virtual chassis
Switches can have different roles in a VC, such as:
- Master: it's the master and holds the virtual chassis's configuration.
- Backup: it's ready to take over the master's role and backs up the VC's configuration.
- LineCard: it acts as a relay in case of a failure on the backup switch (a minimum of 3 switches).
More details are available on Juniper's official website at the following address.
Switches can be organized in two modes within a VC:
- Preprovisioned: assigned in a set way using its serial number:bash
set virtual-chassis preprovisioned set virtual-chassis member 0 serial-number abc123 role routing-engine set virtual-chassis member 1 serial-number def456 role routing-engine set virtual-chassis member 2 serial-number ghi789 role line-card set virtual-chassis no-split-detection #only between two switches# - Non-preprovisioned: assigned by the election algorithm using a priority number:bash
set virtual-chassis member 0 mastership-priority 255 set virtual-chassis member 1 mastership-priority 255 set virtual-chassis member 2 mastership-priority 0
Otherwise, switches are elected by a default algorithm to choose each switch's role within the VC. I recommend method 1.
Several examples:
- Example of a preprovisioned configuration with EX4200 on Juniper's website.
- Example of a non-preprovisioned configuration with EX3300 on Juniper's website.
- Example of both configuration modes with EX3300 on Juniper's website.
Management port in a Virtual chassis
Each switch has a management port, and within a VC we can add a fixed management IP to the VC. The interface used is called vme; if the connection with the master is broken, it moves to the newly elected master, and so on.
Here's a configuration example:
set interfaces vme unit 0 family inet address 192.168.254.1/29
To wrap up, I invite you to finish your introduction with Juniper's VC best practices, you now know the basics of the Virtual chassis under JunOS.
Conclusion
Setting up the virtual chassis on EX4200 and EX3300 switches lets you manage several Juniper switches as a single logical entity, in ring topology or master/backup mode. I detailed the cabling, checking the VCP ports, assigning roles (master, backup, linecard), as well as configuring the management interface (vme). This technology greatly simplifies administering a network infrastructure made up of several physical switches.