The user enables the signaling of the primary LSP path admin-group constraints in the FRR object at the ingress LER with the following CLI command:
config>router>mpls>lsp>fast-reroute>propagate-admin-group
When this command is enabled at the ingress LER, the admin-group constraints configured in the context of the P2P LSP primary path, or the ones configured in the context of the LSP and inherited by the primary path, are copied into the FAST_REROUTE object. The admin-group constraints are copied into the include-any or exclude-any fields.
The ingress LER propagates these constraints to the downstream nodes during the signaling of the LSP to allow them to include the admin-group constraints in the selection of the FRR backup LSP for protecting the LSP primary path.
The ingress LER inserts the FAST_REROUTE object by default in a primary LSP path message. If the user disables the object using the following command, the admin-group constraints are not propagated: config>router>mpls>no frr-object.
The same admin-group constraints can be copied into the Session Attribute object. They are intended for the use of an LSR, typically an ABR, to expand the ERO of an inter-area LSP path. They are also used by any LSR node in the path of a CSPF or non-CSPF LSP to check the admin-group constraints against the ERO regardless if the hop is strict or loose. These are governed strictly by the command:
config>router>mpls>lsp>propagate-admin-group
In other words, the user may decide to copy the primary path admin-group constraints into the FAST_REROUTE object only, or into the Session Attribute object only, or into both.
The PLR rules for processing the admin-group constraints can make use of either of the two object admin-group constraints.