Segment Routing over IPv6 (srv6) Configuration Module

This configuration module configures SRv6 over IS-IS with IBGP using advertised SIDs for global and VPN connectivity services.

Supported SRv6 features:

  • End SIDs (nodes) and End-x SIDs (links), all statically allocated

  • IS-IS routing protocol with SRv6 TLVs

  • SRv6 transport for global IPv4/IPv6 BGP routes

  • BGP IPv4/IPv6 L3VPN over SRv6

The module currently depends on IS-IS and will trigger a configuration error if the isis module is not enabled in the network topology. It supports the L3VPN use case, as well as IPv4 islands over SRv6 (IPv4aaS) and IPv6 transport between SRv6 endpoints.

Platform Support

The following table describes the per-platform support of SRv6-enabled routing protocols:

Operating system

IS-IS

OSPFv3

Cisco IOS XE[1]

✅

❌

Cisco IOS XR[2]

✅

❌

FRR

✅

❌

These platforms can use SRv6 next hops for global IPv4/IPv6 BGP routes:

Operating system

Global IPv4
BGP routes

Global IPv6
BGP routes

Cisco IOS XR

✅

✅

FRR

✅

✅

These platforms support SRv6-based L3VPN services:

Operating system

VPNv4

VPNv6

Cisco IOS XE[1]

✅

✅

Cisco IOS XR[2]

✅

✅

FRR

✅

✅ ❗️

Notes

  • VPNv4 and VPNv6 address families are enabled on IPv6 IBGP sessions

Configurable Global and Node Parameters

  • addressing.srv6_locator – global address pool[3] for allocation of SRv6 locator prefixes, the default prefix is defined in topology.defaults.srv6.locator_pool (5F00::/16, the IANA reserved range defined by RFC9602

  • srv6.allocate_loopback – global flag (default: False) to replace the IPv6 loopback address of each SRv6-enabled node with an IPv6 address allocated from the locator range

  • srv6.bgp – enable BGP with IPv4 and IPv6 address families over SRv6, default IPv4 + IPv6 over iBGP.

  • srv6.vpn – enable BGP with VPNv4 and VPNv6 address families over SRv6. BGP/SRv6 L3VPN is disabled by default.

  • srv6.igp – list of IGP protocols for which to enable SRv6, default [isis]

Node Parameters

  • srv6.locator: an optional IPv6 address prefix to allocate to a given SRv6 node; by default, each node is assigned a unique /48 prefix from the global pool

  • srv6.transit_only: an optional Boolean flag to optimize resource usage and only allocate transit behaviors, not endpoint behaviors

Configurable BGP/SRv6 IPv4/6 and L3VPN Parameters

This module provides 2 parameters that are identical in structure, controlling different BGP address families:

  • srv6.bgp – Controls SRv6 next hops for global IPv4 and IPv6 BGP routes

  • srv6.vpn – Controls VPNv4 and VPNv6 address families

Each parameter could be a boolean (True to enable both IP address families on IBGP sessions), or a dictionary of parameters:

  • ipv4 – enable IPv4/VPNv4 address family

  • ipv6 – enable IPv6/VPNv6 address family

ipv4 and ipv6 parameters could be:

  • Boolean value False to disable the address family within node data (overwriting global defaults)

  • Boolean value True to enable the address family on IBGP sessions

  • A string or a list of ibgp/ebgp keywords[4]

For a tested example, see the SRv6 integration tests.