TLOC extension

Updated: April 24, 2026

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Introduces TLOC extension fundamentals, including implementation over IPv6 and outlining associated limitations and design principles for WAN connectivity.

A TLOC Extension is a Cisco Catalyst SD-WAN feature that

enables a device to access the opposite WAN transport connected to a neighboring device using a TLOC extension interface, and
addresses scenarios where devices cannot connect directly to a single transport and only one device can connect to each transport.

Benefits of TLOC extension

There are scenarios when Cisco IOS XE Catalyst SD-WAN devices cannot connect to a single transport directly and only one device can connect to a single transport. A switch is connected to each transport and the devices connect to each transport through the switches. TLOC extension provides the following benefits:

Eliminates the need for additional switches at branch locations.
Reduces overall solution costs and simplifies network management.

TLOC extension over IPv6

From Cisco IOS XE Catalyst SD-WAN Release 17.11.1a TLOC extension over IPv6 works only if the underlay supports IPv6 addressing on both the Cisco IOS XE Catalyst SD-WAN devices connecting each other.

In the earlier releases, TLOC extension was supported only over IPv4 interfaces.

Supported configurations

This feature supports the following requirements:

Implicit IPv6 ACL on TLOC tunnel interface.
Private and public color TLOC interfaces.
Dual stack support. When both IPv4 and IPv6 are configured, the tunnel is built on top of either IPv4 or IPv6, based on the configuration.
NAT66 support. The limitations of NAT66 also applies to the TLOC extended interface.
Only the Layer 2 setup supports IPv6 TLOC extension. The following interface types supports IPv6 TLOC extension:
- Physical interface
- Physical sub-interface
- Loopback interface
Loopback TLOC interface that is bound to either:
- The WAN transport circuit.
- An extended WAN interface between two Cisco IOS XE Catalyst SD-WAN devices.

Limitations for TLOC extension over IPv6

SIG

Secure Internet Gateway (SIG) is not supported on TLOC extension over IPv6.

NAT64

NAT64 is not supported for TLOC extension over IPv6.

Layer 3 Connectivity

TLOC extension over IPv6 is not supported for Layer 3 connections.

Control connection persistence

When a TLOC configuration is extended to a peer interface and then to the internet service provider, the extended control connections remain active on the peer interface even after the TLOC extension configuration is removed.

Extender interface configuration

In TLOC extension, the extender interface is part of the Cisco Catalyst SD-WAN. However, configuring a tunnel-interface under the extender interface is optional.

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