Connecting EX Series Switches 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. EX4300 switches except EX4300-48MP and EX4300-48MP-S are supported in the leaf role in a QFX5100 VCF. To understand the different hardware configurations supported, see Virtual Chassis Fabric Hardware Overview.
Although best practice is to use all QFX5100 switches in the VCF, you can also use EX4300 switches except EX4300-48MP and EX4300-48MP-S as leaf devices.
Installations with combinations of QFX5100-48T, QFX3600, QFX3500, and EX4300 switches except EX4300-48MP and EX4300-48MP-S as leaf devices in the QFX5100 VCF are called mixed mode. All VCF installations can support 20 total devices, of which four QFX5100 devices can be configured into spine devices.
You can install a VCF in a single rack, multiple racks, or in wire closets. You construct a VCF by configuring and then cabling QSFP+ interfaces into Virtual Chassis ports (VCPs).
On EX4300 switches, QSFP+ ports 0 and 1 are configured as VCP by default. Non-channelized QSFP+ interfaces on EX4300 switches except EX4300-48MP and EX4300-48MP-S can be configured into VCPs. You can also use the SFP+ uplink module ports as VCPs by configuring these ports as VCPs. The SFP+ network ports cannot be configured into VCPs. In EX4300-48MP and EX4300-48MP-S switches, you can use only the built-in QSFP+ ports as VCPs. You cannot configure the ports on the uplink module in EX4300-48MP and EX4300-48MP-S switches to Virtual Chassis ports (VCPs).
Use 40-Gigabit QSFP+ ports as VCPs when available.
Figure 1 shows two QFX5100-24Q spine devices connected to a QFX5100-48S, QFX3600, QFX3500, EX4300, and QFX5100-96S leaf devices using all QSFP+ ports as VCPs.