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Local Breakout Overview

date_range 11-Mar-18

The local breakout feature enables Contrail Service Orchestration (CSO) to route Internet traffic directly from a site in a software-defined WAN (SD-WAN) implementation. In the full mesh topology, local breakout is supported on the branch sites. In the hub-and-spoke topology, local breakout is supported on the on-premise hub site and the spoke site. If local breakout is not enabled on the spoke site, then Internet traffic is routed from the hub site if local breakout is enabled on the hub site. Local breakout is not supported on cloud hub sites.

When creating sites, you need to enable local breakout and configure the WAN links that are used for local breakout traffic on the site. You also need to specify whether the WAN links are used exclusively for local breakout traffic or for both local breakout and non-Internet traffic. If a specific WAN link is used exclusively for local breakout, then overlay tunnels for that WAN link are not created. Enabling a WAN link to be used exclusively for local breakout traffic reduces the number of overlay tunnels created between spoke and hub sites, thereby conserving bandwidth.

You can create a source Network Address Translation (NAT) rule while enabling local breakout on a spoke site. The source NAT rule is interface-based and is implicitly defined and applied to the site. This automatically created source NAT rule is not visible on the NAT Policies page. The automatically created source NAT rule has the least priority among rules and can be overridden by a user-created NAT policy. The automatically created source NAT rule can be enabled and disabled only from the Configuring a Site page. For an on-premise hub site, the option for automatic creation of source NAT rule is not available on the Configuring a Site page, and you need to create a source NAT rule.

You can enable SLA profiles to be associated with local breakout and map the SLA profile to static SD-WAN policies. For SLA profiles that are used for local breakout, you must select a path preference. Static SD-WAN policies are used to route the traffic of the applications defined in the static policies by using the preferred path in the attached SLA profile.

Applications are classified into the following categories:

  • Cacheable applications—Cacheable applications are applications groups that are stored in the application cache when they are recognized by the device. After they are stored in the application cache, subsequent sessions are routed directly through the correct WAN link. Only cacheable applications and application groups are supported during the creation of local breakout-specific static SD-WAN policies.

  • Noncacheable applications—Noncacheable applications are not stored in the application cache and all sessions are first routed through the default path, and then routed to the correct WAN link based on the SD-WAN policy. Noncacheable applications cannot be used for local breakout-specific static SD-WAN policies.

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