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Understand vSRX with Contrail

This section presents an overview of vSRX on Contrail

vSRX on Juniper Networks Contrail

Juniper Networks Contrail is an open, standards-based software solution that delivers network virtualization and service automation for federated cloud networks. It provides self-service provisioning, improves network troubleshooting and diagnostics, and enables service chaining for dynamic application environments across enterprise virtual private cloud (VPC), managed Infrastructure as a Service (IaaS), and Networks Functions Virtualization (NFV) use cases.

You can use Contrail with open cloud orchestration systems such as OpenStack or CloudStack to instantiate instances of vSRX in a virtual environment. Contrail with vSRX provides network services such as firewall, NAT, and load balancing to virtual networks.


vSRX on a KVM hypervisor requires you to enable hardware-based virtualization on a host OS that contains an Intel Virtualization Technology (VT) capable processor.

vSRX Scale Up Performance

Table 1 shows the vSRX scale up performance based on the number of vCPUs and vRAM applied to a vSRX VM along with the Junos OS release in which a particular vSRX software specification was introduced.

Table 1: vSRX Scale Up Performance




Release Introduced

2 vCPUs

4 GB

  • Virtio

  • SR-IOV (Intel X520/X540)

Junos OS Release 15.1X49-D20

5 vCPUs

8 GB

  • Virtio

  • SR-IOV (Intel X520/X540)

Junos OS Release 15.1X49-D70 and Junos OS Release 17.3R1

You can scale the performance and capacity of a vSRX instance by increasing the number of vCPUs and the amount of vRAM allocated to the vSRX. The multi-core vSRX automatically selects the appropriate vCPUs and vRAM values at boot time, as well as the number of Receive Side Scaling (RSS) queues in the NIC. If the vCPU and vRAM settings allocated to a vSRX VM do not match what is currently available, the vSRX scales down to the closest supported value for the instance. For example, if a vSRX VM has 3 vCPUs and 8 GB of vRAM, vSRX boots to the smaller vCPU size, which requires a minimum of 2 vCPUs. You can scale up a vSRX instance to a higher number of vCPUs and amount of vRAM, but you cannot scale down an existing vSRX instance to a smaller setting.


The number of RSS queues typically matches with the number of data plane vCPUs of a vSRX instance. For example, a vSRX with 4 data plane vCPUs should have 4 RSS queues.