Inter-AS Traffic Engineering Limitations

Only LSP hierarchical, or nested, signaling is supported for inter-AS traffic engineered LSPs. Only point-to-point LSPs are supported (there is no point-to-multipoint support).

In addition, the following limitations apply. Any one of these conditions is sufficient to render inter-AS traffic engineered LSPs impossible, even if the above requirements are met.

• The use of multihop BGP is not supported.
• The use of policers or topologies that prevent BGP routes from being known inside the AS is not supported.
• Multiple ASBRs on a LAN between EBGP peers are not supported. Only one ASBR on a LAN between EBGP peers is supported (others ASBRs can exist on the LAN, but cannot be advertised).
• Route reflectors or policies that hide ASBR information or prevent ASBR information from being distributed inside the ASs are not supported.
• Bidirectional LSPs are not supported (LSPs are unidirectional from the traffic engineering perspective).
• Topologies with both inter-AS and intra-AS paths to the same destination are not supported.

In addition, several features that are routine with all LSPs are not supported with inter-AS traffic engineering:

• Admin group link colors are not supported.
• Secondary standby is not supported.
• Reoptimization is not supported.
• Crankback on transit routers is not supported.
• Diverse path calculation is not supported.
• Graceful restart is not supported.

These lists of limitations or unsupported features with inter-AS traffic engineered LSPs are not exhaustive.

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