Segment Routing

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FAQ

What is Segment Routing?

Segment Routing is a traffic-engineering method that steers data across a predefined set of network instructions, rather than leaving every routing decision to each hop. It runs across MPLS or IPv6 networks and is used in WAN, data centre and service-provider environments to control how business-critical applications use bandwidth.

1

Simpler traffic engineering

It reduces separate signalling requirements and per-connection configuration, making large networks easier to manage.

2

Better path control

Traffic can avoid congested or failed links, improving application performance and supporting faster recovery.

3

Compatibility and planning matter

Successful deployment depends on compatible routers, suitable software and careful resilience planning.

The Role of Segment Routing in Modern IT Environments

Segment Routing gives enterprise and service-provider networks greater control over how applications and services move across WAN, cloud, and data centre environments.

The approach you choose determines how precisely you can steer traffic around congestion, how quickly you can fail over when links or routers drop, and whether path control adds simplicity or operational overhead.

As a partner to vendors including Cisco and Juniper, we specify Segment Routing against your requirements, so you're not overinvesting in capability you won't use or underdesigning the resilience, visibility, and policy control your network needs.

How Segment Routing Works

Segment Routing puts a list of path instructions into each packet at the start of its journey. Routers then read each segment in turn and forward the traffic along the chosen path.

For IT teams

This gives IT teams tighter control over WAN paths. It can simplify rollout by avoiding separate traffic-engineering state on each router, improve capacity use, and help protect application performance during failures.

The diagram below shows how segment routing works

Why Organisations Choose Segment Routing

Segment Routing helps organisations control traffic paths, scale WANs and simplify operations while improving resilience across complex networks.


Simplifying Traffic Engineering

Segment Routing uses defined network paths without multiple signalling protocols, making routing policies and performance easier to control.

Improving WAN Scalability

A simplified routing model helps large WANs expand across more sites and connections without excessive per-service configuration.

Optimising Network Paths

Traffic can avoid congested or underperforming links and follow routes better suited to important applications and services.

Reducing Operational Complexity

Path instructions are applied at the network edge, reducing detailed state and repetitive configuration on intermediate routers.

Supporting Modern Service Provider Networks

Segment Routing supports scalable service delivery across provider and carrier networks linking enterprise sites, cloud platforms and data centres.

Enhancing Network Resilience

Pre-planned alternative paths let traffic move quickly around failed links or routers during network disruptions.

Common Enterprise Use Cases

Segment Routing helps enterprises control traffic flow, scalability, resilience, and service performance across complex WAN, cloud, and data centre environments.


Optimising WAN Traffic Paths

Directs traffic along routes chosen for latency, bandwidth, or policy needs instead of relying solely on default shortest-path forwarding.

Simplifying Traffic Engineering

Defines end-to-end paths at the source or controller, reducing signalling overhead and configuration requirements across intermediate routers.

Supporting SD-WAN Architectures

Provides a programmable WAN underlay that steers traffic efficiently between branches, cloud platforms, data centres, and shared network services.

Improving WAN Scalability

Helps large routed WANs grow efficiently without requiring every intermediate device to maintain detailed per-service path information.

Delivering Network Resilience

Supports pre-calculated backup paths and fast rerouting around failed links or routers to minimise disruption to critical services.

Enabling Intent-Based Networking

Allows controllers to apply application-aware path policies aligned to performance, resilience, and service-priority objectives across the WAN.

Key Considerations When Deploying Segment Routing

Policy and control-plane planning prevents path errors, opaque forwarding and service disruption as programmable WAN traffic engineering expands.


01

Traffic Engineering Strategy

Map application constraints, link capacity and failure scenarios to explicit segment-routing policies so engineered paths solve measured network requirements.

02

Routing Policy Design

Define segment identifiers, policy preferences and fallback behaviour carefully so traffic cannot enter unintended paths or bypass required services.

03

WAN Scalability

Model node, prefix, policy and segment-list scale against platform limits so control-plane growth remains supportable across the WAN.

04

Controller Integration

Validate controller protocols, APIs, topology data and policy ownership so automated path changes remain accurate, authorised and auditable.

05

Network Visibility

Confirm telemetry, path tracing, policy-state and performance monitoring capabilities so teams can verify the actual route taken by each service.

06

Service Continuity

Test convergence, repair paths and controller-loss scenarios so critical traffic remains reachable when links, nodes or policy services fail.

Technology Comparison: Segment Routing vs MPLS

Segment Routing often uses an MPLS data plane, so this table compares it with conventional MPLS signalling rather than treating them as unrelated replacements.

Segment Routing MPLS
Path-control architecture Segment Routing steers packets through ordered segment identifiers selected at the ingress and can operate with MPLS labels or an IPv6 data plane. Conventional MPLS assigns labels through protocols such as LDP or RSVP-TE and forwards traffic across established label-switched paths.
Best-fit WAN and service-provider environments Programmable WANs and service-provider networks seeking central path control, automation and reduced signalling state within the core. Established provider and enterprise WANs using mature MPLS services, operational processes and broad multi-vendor support.
Traffic engineering, scale and convergence Simplifies traffic engineering and fast reroute by encoding the intended path at the edge, subject to segment depth and platform scale. Provides proven traffic engineering and service separation, but RSVP-TE designs can maintain more per-path state across intermediate routers.
Control-plane, labels and automation Requires compatible routers, IGP or BGP extensions, segment-identifier governance, telemetry and often controller integration for advanced policy. Uses mature LDP, RSVP-TE, label and VPN operations, with migration planning required when introducing segment-routing control.
What it is not built for Networks whose routers, controllers or operational tools do not support the required SR-MPLS or SRv6 functions consistently. Environments seeking source-routed automation and simpler core state without retaining conventional LDP or RSVP-TE signalling.

Enterprise Platforms We Recommend

Cisco and Juniper platforms suit different routing teams, operational models, and traffic-engineering requirements. Here's where each one fits best.


Juniper Enterprise Routing product

Juniper Enterprise Routing

Best for: Advanced teams running high-scale enterprise or provider-style networks that need programmable path control, scalable traffic engineering, and precise policy across complex routing domains.

Strengths
  • BGP, MPLS, and segment routing support scalable ingress path control
  • Junos OS ties segment routing directly into IGP and BGP policy
  • Fast-reroute policies restore critical traffic quickly after topology changes
  • Junos automation exposes routing telemetry for programmatic WAN control
View Juniper Routers › ›
Cisco Enterprise Routing product

Cisco Enterprise Routing

Best for: Medium-to-large enterprise WANs with Cisco-skilled teams that need application-aware policy, branch consistency, and programmable traffic engineering across distributed sites.

Strengths
  • BGP and segment routing support scalable policy-driven ingress path selection
  • Cisco IOS XE integrates segment routing with IGP and BGP policy
  • Fast-reroute policies bypass failed links and restore services faster
  • Cisco SD-WAN unifies policy, telemetry, and distributed WAN governance
View Cisco Catalyst Routers › ›
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Related Technology Guides

Segment Routing works within broader routed and overlay designs; these guides explain the protocols and architectures that influence path control.

Border Gateway Protocol (BGP)

Discover how BGP supplies reachability while Segment Routing defines the path traffic should take through the network.

Read the guide

EVPN

Review how routed transport can carry EVPN services between sites, fabrics or network domains.

Read the guide

VXLAN

Examine how underlay path control can support traffic moving between VXLAN tunnel endpoints.

Read the guide

Spine-Leaf Architecture

Where programmable paths fit within scalable routed fabrics and larger data centre interconnect designs.

Read the guide

Related Technology Platforms

Explore the routed platforms that can use Segment Routing to control paths across WAN, data centre and performance-sensitive network environments.

Enterprise Routers

Deploy programmable path control across compatible branch, WAN edge and service-provider routing platforms.

View Enterprise Routers

Data Centre Switching

Steer traffic between fabrics, services and external networks using supported routed data centre platforms.

View Data Centre Switching

Core Switching

Apply scalable path selection across high-capacity routed cores connecting enterprise network domains.

View Core Switching Platforms

AI Networking

Control paths for performance-sensitive accelerated traffic where the selected fabric supports Segment Routing.

View AI Networking Platforms

Related Solutions

Segment Routing supports policy-driven paths across WAN and data centre environments, connecting traffic engineering with wider network modernisation.

Networking Solutions

Path policies and service reachability work reliably when Segment Routing is integrated with the wider architecture and given clear operational ownership.

Plan Your Network ›

WAN & Edge Networking Solutions

Application priority, resilience and available capacity can determine WAN paths without maintaining complex traffic-engineering state on every intermediate router.

Build a Resilient WAN ›

Data Centre Networking Solutions

Programmable routes between data centre fabrics and shared services align traffic movement with established performance and routing policies.

Design Your Data Centre Network ›

Data Centre Modernisation Solutions

A staged infrastructure transition validates controller integration, telemetry, failover behaviour and service compatibility before legacy routing is retired.

Modernise Your Data Centre ›
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FAQ

What is Segment Routing and how does it work?

Segment Routing inserts an ordered set of path instructions into traffic, allowing the source router to define how packets move through the network.

Intermediate routers follow those instructions without holding separate state for every end-to-end connection. In larger environments, this can simplify traffic control and make routing policy easier to automate, scale and operate consistently.

What is the difference between SR-MPLS and SRv6?

SR-MPLS typically builds on an existing MPLS estate, while SRv6 uses IPv6 to deliver Segment Routing paths and broader service-level instructions.

SR-MPLS can be a lower-disruption option for organisations already running MPLS, while SRv6 may align better with a wider IPv6 direction. Steel City Consulting can assess infrastructure compatibility, migration effort and operational skills to confirm the right fit.

Is Segment Routing suitable for enterprise networks?

Segment Routing is suitable for larger enterprise WANs and data centre interconnects that need controlled traffic paths, scalable policy automation, or stronger recovery from failures.

Smaller networks with simple routing often see limited benefit from the added architecture and specialist skills required. We can compare organisational scale, application priorities and resilience needs against existing routing capabilities to confirm whether Segment Routing addresses a real operational issue.

How does Segment Routing support traffic engineering?

Segment Routing supports traffic engineering by steering applications across paths chosen for capacity, latency, resilience, or service priority instead of default shortest-route behaviour.

This helps keep critical traffic away from congestion, use preferred infrastructure, or pass through required network services. However, accurate topology and performance data remain essential, because poor path selection can simply shift congestion elsewhere in the network.

How does Segment Routing improve network resilience?

Segment Routing improves resilience by predefining alternative paths so traffic can move around failed links or routers with less disruption.

Effective protection still relies on genuinely separate backup paths and fast failure detection. Steel City Consulting can model and test link, device and shared-route failures, ensuring the design protects against realistic outages rather than only appearing resilient in theory.

What is required to deploy Segment Routing?

Deploying Segment Routing requires compatible routers, supported routing protocols, and management tools able to define, monitor, and troubleshoot traffic paths across the network.

Controller integration, telemetry and interoperability with existing services can also shape the design. Steel City Consulting can validate platform support and introduce the architecture in stages, confirming capacity, path selection and failover behaviour before critical traffic is migrated.

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