The provider edge (PE) stores both local and remote routes and includes a label entry for each route. For distributed platforms,
the per-prefix labels consume memory. When there are many virtual routing and forwarding (VRF) domains and routes, the amount
of memory that the per-prefix labels consume can become an issue.
The MPLS VPN Per VRF Label feature allows the advertisement of a single Virtual Private Network (VPN) label for local routes
throughout the entire VRF. The device uses a new VPN label for the VRF decoding and IP-based lookup to learn where to forward
packets for the PE or customer edge (CE) interfaces.
The following conditions apply when you configure the Per VRF Label feature:
-
The VRF uses one label for all local routes.
-
When you
enable the MPLS VPN Per VRF Label feature, any existing Per VRF Aggregate label is used. If no Per VRF Aggregate label is present,
the software creates a new Per VRF label.
-
When you
enable the MPLS VPN Per VRF Label feature, the CE device’s learned local routes will experience some data loss.
The CE does not lose data when you disable the MPLS VPN Per VRF Label feature because when you disable the feature, the configuration
reverts to the default labeling configuration, which uses the Per VRF Aggregate label from the local nonCE-sourced routes.
-
When you
disable the MPLS VPN Per VRF Label feature, the configuration reverts to the default configuration.
-
A Per VRF label forwarding entry is deleted only if the VRF or the Border Gateway Protocol (BGP) configuration is removed.
Summarization of Label Allocation Modes
The table below defines the label allocations used with various route types.
Table 1. Label Allocation Modes
Route Types
|
Label Mode Default
|
Label Mode: Per VRF Label Feature
|
Local to the PE (connected, static route to NULL0, BGP aggregates), redistributed to BGP
|
Per VRF Aggregate label
|
Per VRF label
|
Locally learned from CE (through EBGP or other PE or CE protocols)
|
Per Prefix label
|
Per VRF label
|