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Disabling Attribute Set Messages on Independent AS Domains for BGP Loop Detection

BGP loop detection for a specific route uses the local autonomous system (AS) domain for the routing instance. By default, all routing instances belong to a single primary routing instance domain. Therefore, BGP loop detection uses the local ASs configured on all of the routing instances. Depending on your network configuration, this default behavior can cause routes to be looped and hidden.

To limit the local ASs in the primary routing instance, you can configure an independent AS domain for a routing instance. The independent domain is separate from the primary routing instance and keeps the AS paths of the independent domain from being shared with the AS path and the AS path attributes of other domains.

By default, independent domains use transitive path attribute 128 (attribute set) messages to tunnel the independent domain’s BGP attributes through the internal BGP (IBGP) core. However, the attribute set message behavior for independent domains is undesired in many cases. If you only want to configure independent domains to maintain the independence of local ASs in the routing instance, and perform BGP loop detection only for the specified local ASs in the routing instance, you can disable the attribute set messages.

1. Select the routing instance that contains the independent domain you want to modify. You can select the routing instance from the following hierarchy levels:
   • [edit routing-instances routing-instance-name]
   • [edit logical-systems logical-system-name routing-instances routing-instance-name]
2. Disable attribute set messages on the independent domain.
   [edit routing-instances instance-name]user@host# set routing-options autonomous-system as-number independent-domain no-attrset

   Tip: When you disable attribute set messages, we recommend that you specify the AS number of the primary routing instance. This ensures that the primary routing instance AS is treated as a local AS in the routing instance and is used for BGP loop detection.

After you specify a routing instance for an independent domain, the local ASs are only associated with that routing instance. That means BGP loop detection uses only the local ASs defined in the routing instance.