Multiple Vrf Support; Rsi; Vrf Table Id Database; Vrf-Interface Mapping - Cisco CRS Configuration Manual

Implementing MPLS Label Distribution Protocol
Benefits to the Customer Carriers
• The MPLS LDP CSC feature removes from the customer carrier the burden of configuring, operating,
and maintaining its own backbone. The customer carrier uses the backbone network of a backbone
carrier, but the backbone carrier is responsible for network maintenance and operation.
• Customer carriers who use the VPN services provided by the backbone carrier receive the same level
of security that Frame Relay or ATM-based VPNs provide. Customer carriers can also use IPSec in their
VPNs for a higher level of security; it is completely transparent to the backbone carrier.
• Customer carriers can use any link layer technology (SONET, Digital Subscriber Line, Frame Relay,
and so on) to connect the CE routers to the PE routers and the PE routers to the P routers. The MPLS
LDP CSC feature is link layer independent. The CE routers and PE routers use IP or MPLS to
communicate, and the backbone carrier uses MPLS.
• The customer carrier can use any addressing scheme and still be supported by a backbone carrier. The
customer address space and routing information are independent of the address space and routing
information of other customer carriers or the backbone provider.

Multiple VRF Support

To support multiple VRFs, IOS XR LDP configuration model is extended to allow VRF submode and per-VRF
configuration and feature or interface enabling.
IOS XR LDP process is not distributed nor it is multi-instance, hence the single LDP process services all the
configured VRFs. In large scale VRF deployment, it is recommended to enable VRF under LDP with appropriate
policies and label filtering.

RSI

To obtain VRF and routing tables' related information, LDP interacts with the router space infrastructure
(RSI) server. For every LDP enabled non-default VRF, LDP registers with RSI to get notifications upon VRF
default (IPv4/IPv6) tables getting created or deleted, and populate the LDP VRF database accordingly.

VRF Table ID Database

A new database is added in the LDP process to keep track of all VRFs enabled under LDP. This database
holds both active as well as forward-reference VRF records. In addition to serving as an LDP context, each
active record of this database also holds VRF's default (IPv4/IPv6 unicast) table IDs.

VRF-Interface Mapping

To enable LDP on an interface for a given address family under a VRF context , it is required to list interface
and its address family explicitly under a LDP VRF submode. LDP does not enforce or check correctness of
the interface and VRF mapping at the time of configuration, and hence configuration may be accepted by
LDP. The interface with incorrect VRF mapping is not made operational by LDP and remains down from the
LDP point of view.
This means that an interface remains LDP operationally down for which either:
• LDP has not received any address update, or
• LDP has received update with different table-id (VRF) than configured under LDP.
MPLS LDP Carrier Supporting Carrier for Multiple VRFs
Cisco IOS XR MPLS Configuration Guide for the Cisco CRS Router, Release 5.1.x
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