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Understanding vSRX with Contrail


This section presents an overview of vSRX on Contrail

vSRX Overview

vSRX is a virtual security appliance that provides security and networking services at the perimeter or edge in virtualized private or public cloud environments. vSRX runs as a virtual machine (VM) on a standard x86 server. vSRX is built on the Junos operating system (Junos OS) and delivers networking and security features similar to those available on the software releases for the SRX Series Services Gateways.

The vSRX provides you with a complete Next-Generation Firewall (NGFW) solution, including core firewall, VPN, NAT, advanced Layer 4 through Layer 7 security services such as Application Security, intrusion detection and prevention (IDP), and UTM features including Enhanced Web Filtering and Anti-Virus. Combined with Sky ATP, the vSRX offers a cloud-based advanced anti-malware service with dynamic analysis to protect against sophisticated malware, and provides built-in machine learning to improve verdict efficacy and decrease time to remediation.

Junos OS Release 18.4R1 supports two software architectures.

Figure 1 shows the high-level vSRX software architecture.

Figure 1: vSRX Architecture

vSRX Architecture

vSRX includes the Junos control plane (JCP) and the Packet Forwarding Engine (PFE) components that make up the data plane. vSRX uses one virtual CPU (vCPU) for the JCP and at least one vCPU for the PFE. Starting in Junos OS Release 15.1X49-D70 and Junos OS Release 17.3R1, multi-core vSRX supports scaling vCPUs and virtual RAM (vRAM). Additional vCPUs are applied to the data plane to increase performance.

Figure 2 shows the high-level vSRX 3.0 software architecture.

Figure 2: vSRX 3.0 Software Architecture
vSRX 3.0 Software Architecture

In vSRX 3.0 software architecture, FreeBSD 11.x is used as the guest OS and the Routing Engine and Packet Forwarding Engine runs on FreeBSD 11.x as single virtual machine for improved performance and scalability. vSRX 3.0 uses DPDK to process the data packets in the data plane. The upgrade from previous versions to vSRX 3.0 is not supported.

vSRX Benefits and Use Cases

vSRX on standard x86 servers enables you to quickly introduce new services, deliver customized services to customers, and scale security services based on dynamic needs. vSRX is ideal for public, private, and hybrid cloud environments.

Some of the key benefits of vSRX in a virtualized private or public cloud multitenant environment include:

  • Stateful firewall protection at the tenant edge

  • Faster deployment of virtual firewalls into new sites

  • Ability to run on top of various hypervisors and public cloud infrastructures

  • Full routing, VPN, core security, and networking capabilities

  • Application security features (including IPS and App-Secure)

  • Content security features (including Anti Virus, Web Filtering, Anti Spam, and Content Filtering)

  • Centralized management with Junos Space Security Director and local management with J-Web Interface

  • Juniper Networks Sky Advanced Threat Prevention (Sky ATP) integration

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.

Release History Table
Starting in Junos OS Release 15.1X49-D70 and Junos OS Release 17.3R1, multi-core vSRX supports scaling vCPUs and virtual RAM (vRAM). Additional vCPUs are applied to the data plane to increase performance.