Routing Configuration Guide, Cisco Catalyst SD-WAN Releases 17.x

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RAR for Cisco IOS XE Catalyst SD-WAN devices

Updated: February 6, 2026

Overview

Describes the deployment topology and how SD-WAN tunnels are established over a PPPoE-RAR underlay network.

Radio-Aware Routing (RAR) is a mechanism that leverages radio interfaces to communicate directly with the Open Shortest Path First version 3 (OSPFv3) protocol, enabling real-time signaling of the presence and link conditions of one-hop routing neighbors.

  • RAR improves routing responsiveness in mobile environments by allowing immediate link state updates.

  • Standard protocol timers may be too slow for rapidly changing mobile network conditions.

  • PPPoE provides the underlying connectivity, with support for OSPFv3 and EIGRP.

  • An AX license is required to enable this feature.

In large mobile networks, factors such as distance and radio obstructions can frequently disrupt connections to routing neighbors. If these disruptions are not reported directly to the routing protocols, the protocols rely on their built-in timers to update neighbor status. However, these protocol timers are typically lengthy, which is not ideal for the dynamic conditions of mobile networks.

Connectivity between two Cisco IOS XE Catalyst SD-WAN devices is established over a PPPoE connection, which features variable bandwidth and limited buffering capacity. OSPFv3 and EIGRP are the supported routing protocols for this deployment.

Mobile Ad Hoc Networks (MANETs)

MANETs facilitate device-to-radio communications by addressing the challenges of integrating IP routing with mobile radio technologies in ad hoc networking environments. MANET routing protocols enable signaling between MANET routers, supporting features such as scope-limited flooding and point-to-point delivery of routing protocol messages within the network.

System components of RAR

The RAR feature uses the MANET infrastructure and includes several components: PPPoE, Virtual Multipoint Interface (VMI), QoS, routing protocol interface, and RAR protocols.

Point-to-Point Protocol over Ethernet PPPoE or PPPoE

PPPoE is a well-defined communication mechanism between the client and the server. In the RAR implementation, radio takes the role of the PPPoE client and router takes the role of the PPPoE server. This allows a loose coupling of radio and router, while providing a well-defined and predictable communication mechanism.

As PPPoE is a session or a connection-oriented protocol, it extends the point to point radio frequency (RF) link from an external radio to an IOS router.

PPPoE Extensions

In the Cisco IOS implementation of PPPoE, each session is represented by a virtual access interface, which connects to a radio neighbor. QoS can be applied on these interfaces using PPPoE extensions.

RFC5578 provides extensions to PPPoE to support credit-based flow control and session-based real-time link metrics, which are very useful for connections with variable bandwidth and limited buffering capabilities (such as radio links).

Virtual Multipoint Interface (VMI)

Though PPPoE Extensions provides most of the setup to communicate between a router and a radio, VMI addresses the need to manage and translate events that higher layers (for example, routing protocols) consume.

In bypass mode, every Virtual Access Interface (VAI) representing a radio neighbor is exposed to the routing protocols OSPFv3 and EIGRP so that the routing protocol directly communicates with the respective VAI for both unicast and multicast routing protocol traffic.

In Aggregate mode, VMI is exposed to the routing protocols (such as OSPF) so these protocols can optimize efficiency.

When the network neighbors are viewed as a collection of networks on a point-to-multipoint link with broadcast and multicast capability at VMI, VMI aggregates the multiple virtual access interfaces created from PPPoE. VMI provides a single, multi-access Layer 2 interface with broadcast capability. Using a single interface for the routing protocol reduces the size of the topology database without impacting network integrity. The VMI layer:

  • Redirects unicast routing protocol traffic to the appropriate P2P link (Virtual-Access interface)

  • Replicates multicast or broadcast traffic as needed

RAR architecture

Summary

The topology shows the RAR deployment on Cisco IOS XE Catalyst SD-WAN devices.

Workflow

Figure 1. RAR architecture

  • The four Cisco IOS XE Catalyst SD-WAN devices connect to each other through a radio connected to a physical interface on the device

  • PPPoE-RAR configurations happen on all three routers and once the underlay RAR network is established, the Cisco Catalyst SD-WAN tunnels form on the network.

  • The loopback interface acts as a WAN interface and binds to the Virtual Multipoint interface (VMI). The VMI interface in turn binds to the physical interface

  • The PPP connections between any two devices act as the underlay network.

  • The Cisco Catalyst SD-WANCisco SD-WAN Manager tunnels are established over the PPPoE-RAR underlay network.

  • Cisco SD-WAN Manager, Cisco SD-WAN Controller, and Cisco SD-WAN Validator connect through a radio connection in the deployment scenario.

Benefits of RAR

The RAR feature offers these benefits:

  • Provides faster network convergence through immediate recognition of changes.

  • Enables routing for failing or fading radio links.

  • Allows easy routing between line-of-sight and non-line-of-sight paths.

  • Provides faster convergence and optimal route selection so that delay-sensitive traffic, such as voice and video, is not disrupted

  • Provides efficient radio resources and bandwidth usage.

  • Reduces impact on the radio links by performing congestion control in the router.

  • Allows route selection based on radio power conservation.

  • Enables decoupling of the routing and radio functionalities.

  • Provides simple Ethernet connection to RFC 5578, R2CP, and DLEP compliant radios.

Supported devices for RAR

These platforms support RAR:

  • Cisco 4000 Series Integrated Services Routers

  • Cisco 1000 Series Integrated Services Routers

  • Cisco ASR 1000 Series Aggregation Services Routers

  • Cisco CSR 1000 Series Cloud Service Routers

  • Cisco CSR 8000 Series Cloud Service Routers

Restrictions for RAR

The Radio Aware Routing feature has these restrictions:

  • The Dynamic Link Exchange Protocol (DLEP) and Router to Radio Control Protocol (R2CP) protocols are not supported.

  • Multicast traffic is not supported in aggregate mode.

  • Cisco High Availability technology is not supported.

Prerequisites for RAR

The RAR configuration requires Mobile Ad-hoc Networks (MANETs) support. To use the PPP over Ethernet (PPPoE) and virtual multipoint interface (VMI) features for RAR, a unified representation of the MANET to routing protocols (OSPFv3 or EIGRP) is required.