Juniper Ren 2 Link [updated] ✔

Review: Juniper Networks EX4300 Series (Model: EX4300-48P) Firmware Version: Junos OS 15.1R2.9 Reviewer: Network Infrastructure Specialist

How to Check the Status of Your REN 2 Link

You won't see interface ren-2/0/0 in a standard show interfaces terse. Instead, use these operational commands:

What it is

Juniper REN 2 Link (Remote Ethernet Network 2 Link) is a transport/networking capability used in Juniper network environments to extend Layer 2 Ethernet connectivity across metropolitan or wide-area networks. It enables remote sites to appear as if they are on the same Ethernet segment, supporting VLAN transparency, MAC learning, and typical Ethernet services over a packet or optical fabric. juniper ren 2 link

2. Detailed REN Interface Statistics

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.

A. Enabling GRES (Required for REN 2 utilization)

Without GRES, the REN 2 link sits idle except for basic keepalives. Key indicators : Zero errors, zero drops, and

set chassis redundancy graceful-switchover
set chassis redundancy routing-engine 0 master
set chassis redundancy routing-engine 1 backup
commit

Best Practices for REN 2 Link Health

Monitor the internal Ethernet switch: On chassis-based systems, the REN link passes through a midplane or switch card. A single failed fan tray can overheat the backplane and kill the REN 2 link.
Enable Graceful Routing Engine Switchover (GRES): This keeps the REN 2 link active during software upgrades.
Run show system alarms: Many REN 2 issues first appear as a minor alarm: "Redundancy link degraded."

Part 6: Advanced Scenarios – REN 2 Link in Virtual Chassis and Multi-Chassis LAG

On larger platforms (NX2020, PTX10008), the concept of REN 2 extends to REN 2 over fabric planes – but there’s nuance.