Effective Cisco IOS XR Release 6.3.1, this feature enables the support for Connectivity Fault Management (CFM) on subinterfaces. CFM provides immediate update if there is any breakage in the intermittent links.

To implement this feature, the following command is updated to include the subinterface path ID:

interface {HundredGigE | TenGigE | GigE | Bundle-Ether} interface-path-id.subinterface

Note	The CFM on subinterfaces is supported only on Cisco NCS 5001 and Cisco NCS 5002 Routers, and not supported on Cisco NCS 5011 Routers.

For more information, see Configuring CFM MEPs section of the Configuring Ethernet OAM chapter of the Interface and Hardware Component Configuration Guide for Cisco NCS 5000 Series Routers, IOS XR Release 6.3.x.

Switched Port Analyzer (SPAN), which is also called port mirroring or traffic mirroring, enables you to monitor network traffic passing in, or out of, a set of ports. You can then pass this traffic to a destination port on the same router.

Traffic mirroring copies traffic from one or more source ports and sends the copied traffic to one or more destinations for analysis by a network analyzer or other monitoring device. However, traffic from one source port can be copied to only one destination port. Traffic mirroring does not affect the flow of traffic on the source ports, and allows the mirrored traffic to be sent to a destination port.

For more information, see the Configuring Traffic Mirroring chapter of the Interface and Hardware Component Configuration Guide for Cisco NCS 5000 Series Routers, IOS XR Release 6.3.x.

Topology-Independent Loop-Free Alternate (TI-LFA) uses segment routing to provide link protection in topologies where other fast reroute techniques cannot provide protection. The goal of TI-LFA is to reduce the packet loss that results while routers converge after a topology change due to a link failure. Rapid failure repair (< 50 msec) is achieved through the use of pre-calculated backup paths that are loop-free and safe to use until the distributed network convergence process is completed.

For more information, see the Segment Routing Configuration Guide for Cisco NCS 5000 Series Routers.

The maximum size of the Segment Routing Global Block (SRGB) is increased from 65,536 to 262,143.

Priority Queuing (PQ) in strict priority mode ensures that one type of traffic is sent, possibly at the expense of all others. For PQ, a low-priority queue can be detrimentally affected, and, in the worst case, never allowed to send its packets if a limited amount of bandwidth is available or the transmission rate of critical traffic is high. Strict PQ allows delay-sensitive data, such as voice, to be de-queued and sent before packets in other queues are de-queued.

For more information, see the Modular QoS Configuration Guide for Cisco NCS 5000 Series Routers, IOS XR Release 6.3.x.

BFD over Bundle feature enables Bidirectional Forwarding Detection (BFD) sessions to monitor the status of individual bundle member links. BFD informs the bundle manager immediately when one of the member link goes down, and reduces the bandwidth of bundle.

For more information, see the Routing Configuration Guide for Cisco NCS 5000 Series Routers, IOS XR Release 6.3.x.

Bidirectional forwarding detection (BFD) provides low-overhead, short-duration detection of failures in the path between adjacent forwarding engines. BFD allows a single mechanism to be used for failure detection over any media and at any protocol layer, with a wide range of detection times and overhead. The fast detection of failures provides immediate reaction to failure in the event of a failed link or neighbor.

For more information, see the Routing Configuration Guide for Cisco NCS 5000 Series Routers, IOS XR Release 6.3.x.

Support for Layer 2 (L2) sub-interfaces to work with BVI interface in a bridge domain has been added in this release. The L2 sub-interfaces must have a rewrite configuration to pop the outer tag in Ingress direction and push the outer tag on the packet in egress direction. The outer tag that is to be pushed in egress direction is based on the interface encapsulation. The support is added only for single tag sub-interfaces. Double tagged sub-interfaces that work with BVI interface in a bridge domain are not supported.

For more information, see the Interface and Hardware Component Configuration Guide for Cisco NCS 5000 Series Routers, IOS XR Release 6.3.x.

There is the possibility of loops due to redundant connections across switches(bridge-domains). Spanning Tree Protocol (STP) helps in avoiding loops by transitioning the ports on the L2 network to appropriate states. The Multiple Spanning Tree Protocol (MSTP) is an STP variant that allows multiple and independent spanning trees to be created over the same physical network.

For more information on this feature, see the Spanning Tree Protocol chapter in the L2VPN and Ethernet Services Configuration Guide for NCS 5000 Series Routers,IOS XR Release 6.3.x

Cisco IOS XR Release 6.3.1 supports the configuration of multiple VRFs and multi-VRF docker containers on XR. The applications hosted in third-party LXCs can communicate with VRFs configured on XR, after east-west communication has been enabled on the VRFs.

For more information, see the Configuring Multiple VRFs for Application Hosting, and Configuring a Docker with Multiple VRFs sections in the Cisco IOS XR Application Hosting Configuration Guide .

From Cisco IOS XR Release 6.3.1 onwards, routers using BGP LU can use ECMP to equally distribute the traffic along all available paths to a chosen destination. BGP uses the 5-tuple address hash for ECMP load balancing. You can enable either the DLB or ECMP method of load balancing by using the hw-module command in global configuration mode.

Note	BGP labelled unicast (LU) is not supported over MPLS-TE.

For more information, see the Segment Routing Configuration Guide for Cisco NCS 5000 Series Routers.

BGP Autodiscovery refers to the process of finding all the provider edge routers that participates in a given VPWS or VPLS instance. Once the PEs are discovered, pseudowires (PWs) are signaled and established across each pair of PE routers. BGP autodiscovery eliminates the need to manually provision VPLS/VPWS neighbors and thereby enables each PE router to discover the other provider edge (PE) routers that are part of the same domain.

For more information on this feature, see the BGP Autodiscovery with BGP/LDP Signalling chapter in the BGP Configuration Guide for Cisco NCS 5000 Series Routers, IOS XR Release 6.3.x

Pseudowire over MPLS-TE feature allows you to send the l2vpn traffic over an MPLS-TE tunnel. To send the l2vpn traffic over an MPLS-TE tunnel, you need to set up an MPLS TE tunnel between the PE routers and specify it as the preferred path for l2vpn traffic.

For more information about configuring Pseudowire over MPLS-TE feature, see MPLS Configuration Guide for Cisco NCS 5000 Series Routers.

The Storm Control feature allows you to monitor the incoming broadcast, multicast, and unknown unicast packets and reduces the flooding of the LAN ports. This feature prevents VPLS bridge disruption by suppressing traffic when the number of packets reaches configured threshold levels. You can configure separate threshold levels for different types of traffic on an access circuit (AC) under a VPLS bridge.

For more information on this feature, see the Storm Control chapter in the L2VPN and Ethernet Services Configuration Guide for Cisco NCS 5000 Series Routers, Release 6.3.1.

To see the list of actions and an example to use a System Admin action, see Components to Use Data Models chapter in the Programmability Configuration Guide for Cisco NCS 5000 Series Routers .

This feature enables Unidirectional Link Detection (UDLD) support for NCS 5000 that allows you to configure each interface. The interface must be a physical ethernet interface. UDLD is a single-hop physical link protocol for monitoring an ethernet link, including both point-to-point and shared media links. This is a Cisco-proprietary protocol to detect link problems, which are not detected at the physical link layer.

For more information, see the Configuring Ethernet OAM chapter in the Interfaces and Hardware Component Configuration Guide for NCS 5500 Series Routers.

Telemetry provides a mechanism to stream data from the router at regular intervals. Event-based telemetry is used to collect data when a state transition occurs. This feature optimises the need to collect state information even when a change in the state does not occur, thus eliminating the data overhead at the router and the receiver.

For more information about state transitions, and collecting event-based telemetry data, see Configure Event-based Telemetry chapter in the Telemetry Configuration Guide for Cisco NCS 5000 Series Routers .

IPv6 Stateless Address Auto Configuration (SLAAC) is supported on management interface. This feature enables automated provisioning of the routers.

To see how to enable IPv6 SLAAC, see Advanced Configuration and Modification of the Management Ethernet Interface chapter in the Interface and Hardware Component Configuration Guide for Cisco NCS 5000 Series Routers .

The enhancments to model-driven telemetry (MDT) includes:

• VRF-aware MDT, sourced from L3 VRF interface

• gRPC protocol supports sending and receiving traffic on a VRF

• Support for JSON encoder

For more information, see Configure Model-based Telemetry chapter in the Telemetry Configuration Guide for Cisco NCS 5000 Series Routers .

There are no caveats in this release.