Connecting a QFX3500 or QFX3600 Switch in a QFX5100 Virtual Chassis Fabric
A Juniper Networks QFX5100 Virtual Chassis Fabric (VCF) is constructed using a spine-and-leaf architecture and topology. In the spine-and-leaf architecture, each spine device is interconnected to each leaf device. A VCF supports up to 20 total devices, and up to 4 devices can be configured into spine devices. QFX3500 or QFX3600 devices are supported in the leaf role in a QFX5100 VCF. To understand the different hardware configurations supported, see Virtual Chassis Fabric Hardware Overview.
Although the best practice is to use all QFX5100 switches in a QFX5100 VCF, you can use QFX3500 or QFX3600 switches as leaf devices.
You can install a VCF in a single rack, multiple racks, or in wire closets. You construct a VCF by cabling and then configuring SFP+ or QSFP+ interfaces into Virtual Chassis ports (VCPs). All non-channelized QSFP+ uplink interfaces on QFX3600 and QFX3500 switches can be configured into VCPs. All fixed SFP+ interfaces on QFX3500 switches can also be configured into VCPs.
Use 40-Gigabit QSFP+ ports as VCPs.
Figure 1 shows two QFX5100-24Q spine devices connected to a QFX5100-48S, QFX3600, QFX3500, QFX5100-96S, EX4300, and QFX5100-48T leaf devices using all QSFP+ ports as VCPs. A VCF with more than one model in the design is called mixed-mode.
