show fabric statistics
On modular systems, this shows the fabric planes. A failed "REN 2" might appear as Plane 2: Link status: Down.
Even though it's an internal link, Junos exposes it as a network interface:
show interfaces ren2
Sample output:
Physical interface: ren2, Enabled, Physical link is Up
Link-level type: Ethernet, MTU: 1500, Speed: 10Gbps
Device flags : Present Running
Interface flags: Point-To-Point
Last flapping : 3 days ago
Input packets : 489123402, Output packets: 512349123
Errors: 0, Drops: 0
Key indicators: Zero errors, zero drops, and a steady packet count.
The Ren 2 is a specific generation of Juniper’s proprietary J-Chip based fabric interconnect. It is responsible for carrying fabric traffic between line cards (FPCs – Flexible PIC Concentrators) and switch fabric cards (SFCs) or between separate chassis in a clustered configuration (e.g., in a Juniper MX2020 or PTX10008 with multiple routing engines). juniper ren 2 link
More precisely, the Ren 2 Link enables:
The Juniper REN 2 Link is not a marketing buzzword—it's the silent workhorse of high-availability routing. Treat it with respect. Check it monthly, log its status, and never ignore a "backup RE not ready" warning. show fabric statistics
Because when the master Routing Engine finally crashes, that REN 2 link is the only thing standing between a seamless failover and a panicked 3 AM outage.
Have you encountered a "REN 2 Link" error on your Juniper gear? Share your show log messages output in the comments below. On modular systems, this shows the fabric planes
The system sends keepalives every 1 second by default. In congested backplane scenarios, you can adjust:
set chassis redundancy ren-keepalive-threshold 500
set chassis redundancy ren-keepalive-interval 2000
But be warned: Changing these without JTAC guidance can cause false failovers.