As mentioned earlier, I’ve been playing with using a Juniper NFX250 as a backup home router for the past month or two. The NFX line (and the NFX250 specifically) is kind of a weird beast. It has most of the capabilities of an SRX, while adding the ability to run high-bandwidth virtual machines directly on the router. It looks like it’s supposed to sort of sit next to the SRX1500 or maybe SRX380 in Juniper’s lineup, while being much cheaper than either. The NFX250 lists for $4,700–$8,500 depending on the configuration, vs $11,000 for the SRX1500 or $14,295 for the SRX380. At those prices, none of these would make a very interesting home router, much less a home backup router. What makes the NFX250 interesting to me is that it’s available on eBay, frequently for under $400. That’s not too shabby for a 2x10GbE + 12xGbE router that can supposedly handle around 10 Gbps of traffic.

In fact, the Juniper MX150 is really the same hardware with different software; Juniper claims that it’s good for 20 Gbps.

My NFX250 next to a few Unifi switches.

Under the hood, the NFX250 is mostly just a PC with a Xeon-D 15xx CPU. The NFX250-S1, -S1E, and S2 have a 6-core CPU, while the down-specced NFX250-LS1 only has 4 cores. Other than that, the only difference between the models is the amount of RAM and SSD included. Since the NFX250 uses DDR4 RAM and M.2 2260 SATA SSDs, it’s not particularly difficult or expensive to upgrade any of the models beyond the NFX250-S2 spec of 32GB RAM/400 GB SSD, if you need it.

Note that I said “mostly just a PC” above; the entertaining thing about the NFX250 (and, frankly, the most frustrating part about it) is all of the front panel Ethernet ports (except the management port) are actually connected to a managed Ethernet switch chip, and the switch chip is then wired into the PC inside with 2x10GbE links.

The NFX250 runs Linux, and dumps both internal 10GbE interfaces into a software switch (OVS, specifically). Then the NFX software lets you run VMs and connect them to the software switch in various ways. Managment of the NFX is done via a Junos VM that provides pretty much all of the abilities of a Juniper SRX. By and large, you wouldn’t know that you’re talking to a FreeBSD/Junos VM on top of Linux, right up to the point where you start trying to configure interfaces. Then things get strange.

The front panel interfaces are named ge-0/0/0 through ge-0/0/11 plus xe-0/0/12 and xe-0/0/13, following Juniper’s usual naming conventions. If this was an SRX and you wanted to assign an IP address of to ge-0/0/0, then you’d just run something like

> set interfaces ge-0/0/0 unit 0 family inet address

With the NFX, you rapidly discover that family inet isn’t supported on any of the internal interfaces. Only family ethernet-switching. So how do you use this as a router? Easy… ish.

> set vlans my-vlan vlan-id 100
> set interfaces ge-0/0/0 unit 0 interface-mode access
> set interfaces ge-0/0/0 unit 0 family ethernet-switching vlan members my-vlan
> set interfaces sxe-0/0/0 unit 0 family ethernet-switching vlan members my-vlan
> set interfaces ge-1/0/0 vlan-tagging
> set interfaces ge-1/0/0 unit 100 vlan-id 100
> set interfaces ge-1/0/0 unit 100 family inet address

In short, you need to create a VLAN, map your ge-0/0/x port onto that VLAN, make sure that sxe-0/0/0 includes the VLAN as well, and then add a new unit to ge-1/0/0 to handle that VLAN’s traffic.

Where does ge-1/0/0 come from? It’s a purely virtual beast that hides inside of the NFX250. Entertainingly, even though Junos calls it ge-1/0/0 (which implies that it’s a regular Gigabit Ethernet port), show interface ge-1/0/0 thinks that it’s really a 10GbE link (which Junos usually calls xe-x/x/x, not ge-x/x/x). A half-duplex 10G link, for some reason:

> show interfaces ge-1/0/0
Physical interface: ge-1/0/0, Enabled, Physical link is Up
  Interface index: 170, SNMP ifIndex: 540
  Link-level type: Ethernet, ... Link-mode: Half-duplex, Speed: 10Gbps, ...

Whatever, it’s virtual.

This all seems less odd if you realize that it’s really just a “Router On A Stick” config internally. If you’d like a more traditional Router On A Stick setup, then Junos will happily let you set up VLAN trunks (... family ethernet-switching interface-mode trunk) and share VLANs across interfaces just like a perfectly normal L2 switch.

In Part 2, I’ll jump into some of the weirdness around NFXs, where they behave differently from SRXes. Then I’ll move on to discuss Virtual Network Functions, which is why Juniper made NFXes weird.

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