Flexible Algorithm validation method is based on segment identifier (SID) label and label assigner, instead of being based on IP address. The assigner is validated against the topology prefix information provided by the SR-PCE database. If the assigner is valid, then the label given is also validated against the SR-PCE database. On the egress side, the destination label is contained in a new SR Label sub-TLV. This label is verified against a SID list provided by the SR-PCE.

See Segment Routing Ping and Traceroute for Flexible Algorithm .

This feature introduces support for “include-all” and “include-any” affinity constraints for configuring Segment Routing Flexible Algorithm for IS-IS.

See the Configuring Flexible Algorithm .

Anycast routing enables the steering of traffic toward multiple advertising nodes, providing load-balancing and redundancy. Packets addressed to an Anycast address are forwarded to the topologically nearest nodes. If an advertising node becomes unavailable or unreachable while still advertising its Anycast SID, traffic could still be routed to the node and, as a result, get dropped.

The Segment Routing Conditional Prefix Advertisement for IS-IS feature allows a node to advertise its loopback address when it’s connected to the domain, and to track the loopback addresses of the other nodes in the domain. If a node becomes unavailable or unreachable, it will stop advertising its loopback address, allowing for a new path to be computed.

See the Conditional Prefix Advertisement .

ECMP-FECs are used for any ECMP programming on the system, such as unlabeled ECMP, MPLS LSP ECMP, VPN multipath, and EVPN multi-homing.

The Segment Routing Label Edge Router (LER) ECMP-FEC Optimization feature allows ECMP-FEC optimization originally developed for Label Switched Router (LSR) nodes (MPLS P) to be enabled on LER (Layer 3 MPLS PE) routers.

The SR ECMP-FEC optimization solution minimizes ECMP-FEC resource consumption during underlay programming for an SR-MPLS network. This feature supports sharing the same ECMP-FEC, regular FEC, and Egress Encapsulation DB (EEDB) entries for all /32 IPv4 Segment Routing prefixes with the same set of next hops.

See Segment Routing ECMP-FEC Optimization.

Modern microwave devices support adaptive modulation schemes to prevent a complete loss of signal. Adaptive modulation schemes allow the devices to continue to operate during periods of degradation, but at a reduced bandwidth. However, to fully take advantage of this, it's necessary to convey the decrease in bandwidth to the head-end router so that appropriate actions can be taken. Otherwise, the link may become saturated and traffic dropped arbitrarily.

A generic solution to this is a Connectivity Fault Management (CFM) extension to send Bandwidth Notifications Messages (BNM) to Maintenance Endpoints (MEPs) on the corresponding interface on the head-end router. To be flexible in the actions taken, the choice of solution uses Embedded Event Manager (EEM) to invoke operator written TCL scripts

See CFM Adaptive Bandwidth Notifications

BFD-triggered Fast Reroute feature allows you to obtain link and node protection by using the Bidirectional Forwarding Detection (BFD) protocol to provide fast forwarding path failure detection times for all media types, encapsulations, topologies, and routing protocols. In addition to fast forwarding path failure detection, BFD provides a consistent failure detection method for network administrators.

See BFD-Triggered FRR.

The Per-VLAN Rapid Spanning Tree (PVRST) is the IEEE 802.1w (RSTP) standard implemented per VLAN. PVRST uses point-to-point wiring to provide rapid convergence of the spanning tree. The spanning tree reconfiguration occurs in less than one second with PVRST.

See Per-VLAN Rapid Spanning Tree.

The Multiple Spanning Tree Protocol (MSTP) is a Spanning tree protocols (STP) variant that allows you to create multiple and independent spanning trees over the same physical network. You can configure the parameters for each spanning tree separately. You can select different network devices as the root bridge or different paths to form the loop-free topology. Therefore, you can block a given physical interface for some of the spanning trees and unblocked for others.

See Multiple Spanning Tree Protocol and Multiple Spanning Tree Protocol Commands

The Highest Random Weight (HRW) Mode for EVPN DF Election feature provides optimal load distribution of Designated Forwarder (DF) election, redundancy, and fast access. It ensures a nondisruptive service for an Ethernet Segment (ES) irrespective of the state of a peer DF.

See Highest Random Weight Mode for EVPN DF Election.

The EVPN Single-Active Multihoming for Anycast Gateway IRB feature supports single-active redundancy mode. In this mode, the provider edge (PE) nodes locally connected to an Ethernet Segment load balance traffic to and from the Ethernet Segment based on EVPN service instance (EVI). Within an EVPN service instance, only one PE forwards traffic to and from the Ethernet Segment (ES). This feature supports intersubnet scenario only.

See EVPN Single-Active Multihoming for Anycast Gateway IRB

With this feature, in addition to setting ingress action such as traffic class and QoS group, you can also mark DSCP in the packet header at ingress.

See Ingress Short-Pipe.

The Rewrite of Priority Tag feature allows you to configure rewrite tag for a priority-tagged VLAN. This feature removes the priority-tagged VLAN in the ingress direction and adds the priority-tagged VLAN in the egress direction.

See Rewrite of Priority Tag.

Hot Standby Router Protocol (HSRP) is supported. The HSRP is an IP routing redundancy protocol designed to allow for transparent failover at the first-hop IP router. HSRP provides high network availability, because it routes IP traffic from hosts on networks without relying on the availability of any single router. HSRP is used in a group of routers for selecting an active router and a standby router. An active router is the router of choice for routing packets whereas a standby router is a router that takes over the routing duties when an active router fails, or when pre-set routing conditions are met.

See Implementing HSRP .

See HSRP Commands.

The EVPN Bridging and VPWS Services over BGP-LU Underlay feature allows you to configure end-to-end EVPN services between data centers (DCs). This feature allows you to perform ECMP at three-levels: transport, BGP- LU, and service.

This feature supports the following services:

• IRB VRF over BGP-LU over IGP (SR or non-SR (LDP, IGP))

• EVPN Aliasing over BGP-LU over IGP (SR or non-SR (LDP, IGP))

• VPWS over BGP-LU over IGP

See EVPN Bridging and VPWS Services over BGP-LU Underlay .

BFD on Bridge Group Virtual Interface (BVI) feature, with the IRB functionality, provides the ability to route between a bridged domain and a routed domain.

Using the Integrated Routing Bridging (IRB) functionality, you can configure a router for routing and bridging the same network layer protocol, on the same interface. This functionality allows the VLAN header to be maintained on a frame while it transits a router from one interface to another. The BVI is a virtual interface within the router that acts like a normal routed interface that does not support bridging but represents the comparable bridge group to routed interfaces within the router.

See BFD over BVI.

The Multisegment Pseudowire feature allows you to extend L2VPN pseudowires across an inter-AS boundary or across two separate MPLS networks. A multisegment pseudowire connects two or more contiguous pseudowire segments to form an end-to-end multi-hop pseudowire as a single point-to-point pseudowire. These segments act as a single pseudowire, allowing you to:

• Manage the end-to-end service by separating administrative or provisioning domains.

• Keep IP addresses of provider edge (PE) nodes private across interautonomous system (inter-AS) boundaries. Use IP address of autonomous system boundary routers (ASBRs) and treat them as pseudowire aggregation routers. The ASBRs join the pseudowires of the two domains.

See Multisegment Pseudowire.

Forwarding Information Base (FIB) Per-Prefix Out of Resource (OOR) Handling Improvement feature enables you to create a graceful out of resource handling for Forwarding Equivalence Class (FEC) resources.

See FIB Per-Prefix Out of Resource Handling Improvement.

Beginning this release, you can:

• classify packets at the ingress on L3 subinterfaces for (CoS, DEI) for IPv4, IPv6, and MPLS flows.

• perform Layer 2 marking of Ethernet packets for (CoS, DEI) for IPv4, IPv6, and MPLS flows in the egress direction on L3 subinterfaces.

See Packet Classification Overview and QoS L2 Re-Marking of Ethernet Packets on L3 Flows in Egress Direction on L3 sub-interfaces.

The command, hw-module profile qos ipv6 short-l2qos-enable is introduced.

IPv4 BFD Multihop feature is supported in MPLS LDP and Segment Routing.

See IPv4 Multihop BFD.

On ingress direction, after matching the traffic based on either the IP Precedence or DSCP value, you can set it to a particular discard-class. At the egress, a congestion avoidance technique such as weighted random early detection (WRED) then uses the assigned discard-class value to determine the probability that a packet is dropped. With the introduction of this feature, if you now set a discard-class of 3, the packet is dropped at ingress itself.

See Packet Marking.

The command, set discard-class is modified.

The VPLS VFI with BVI as Routed Interface feature allows you to route the VPLS PW traffic dynamically over BVI interface.

Integrated routing and bridging (IRB) enables you to route the packets received from a host on a bridge group and a routed interface using a Bridge-Group Virtual Interface (BVI). The BVI is a virtual interface configured on the router which acts as a gateway routed interface towards the core network.

See VPLS VFI with BVI as Routed Interface.

Currently, the router supports upto 2K labelled prefixes with Equal Cost Multi Path (ECMP). From this release onwards, with the introduction of the Interior Gateway Protocol (IGP) Destination-based Load Balancing (DLB) feature, the router can support higher scale of labelled prefixes.

See Interior Gateway Protocol (IGP) Destination-based Load Balancing (DLB).

This feature enables you to provide the names of the database, for example LPM, EXT-TCAM, and LEM, in which any prefix of any packet is updated. With this feature, you can efficiently manage your network resources because it allows you to understand the scaling of prefixes. This feature also helps you to understand why a particular IP address configuration for a device fails and thereby helps you in debugging.

See Implementing Cisco Express Forwarding.

See Cisco Express Forwarding Commands .

The Flooding Disable feature prevents forwarding of Broadcast, Unknown-unicast and Multicast (BUM) traffic on the bridge domain. You can disable flooding of BUM traffic at the bridge level or at the interface level. By disabling flooding at the bridge level, you can prevent forwarding of BUM traffic on attachment circuit (AC) and pseudowire (PW).

You can also disable only unknown unicast traffic at the bridge level or at the interface level. By disabling flooding of unknown unicast traffic at the bridge level, you can prevent forwarding of unknown unicast traffic on attachment circuit (AC) and pseudowire (PW).

By disabling flooding of unknown unicast traffic at the interface level, you can prevent forwarding of unknown unicast traffic on AC alone.

See Flooding Disable.

Support for a notification mechanism using SNMP trap and syslog messages when a TLS certificate is approaching its expiry.

The notifications are sent at the following intervals:

• First notification—This notification is sent 60 days before the expiry of the certificate.

• Repeated notifications—After the first notification, subsequent notifications are sent every week until a week before the expiry of the certificate. In the last week, notifications are sent every day until the certificate expiry date.

See Expiry Notification for PKI Certificate .

A congestion management system for telemetry data allows each destination a maximum of 4000 outstanding messages. The events are throttled when the outstanding messages exceed 3000; throttling of cadence messages happen when outstanding messages exceed 250. Events have higher priority than cadence messages.

See Congestion Management for Telemetry Data.

The OpenConfig (OC) data models are defined by the OC community to create configuration and retreive operational state data of the network. The following data models are revised to provide additional capabilities:

• The OC Integrated Intermediate System-to-Intermediate System data model, oc-isis, is enahnced to provide support for additional paths in the data model.

• The oc-policy data model contains general data definitions for use in routing policy. It can be imported by modules that contain protocol-specific policy conditions and actions.

• Enhancement of gNMI specification to include updates from version 0.4.0 to version 0.6.0. Support is extended for the following gNMI features:

  • gNMI support for multiple client roles and primary arbitration

  • Path Target

  • gNMI service registration with the gRPC reflection service to allow clients to determine that gNMI is available on the target

See Revised OpenConfig Data Models for Network Programmability

gRPC Network Operations Interface (gNOI) defines a set of gRPC-based microservices for executing operational commands on network devices.

See gRPC Network Operations Interface

Y.1564 or Ethernet Service Activation (or performance test methodology) is a testing procedure which tests service turn-up, installation and troubleshooting of Ethernet-based services.

Y.1564 allows simultaneous testing of multiple Ethernet services and measures. It validates the different service level agreements (SLAs) to ensure the service meets guaranteed performance settings in a controlled test time. It helps to ensure all the services carried by the network meet the SLA objectives at the maximum committed rate proving that under maximum load, the network devices and paths can support the traffic as designed, even under stress.

See Y.1564 - Ethernet Service Activation Test .

Support to retrieve information at thread level to identify heavy processes on the system that can be optimized through network design. A thread is a sequence of instructions to be executed within a program.

• Enhanced Cisco-IOS-XR-wdsysmon-fd-oper.yang data model to include CPU utilization at thread level for each running process

• Support Cisco-IOS-XR-procthreadname-oper.yang data model to query thread-level details such as thread name, priority, state, stack size of a running processes

See Retrieve Process Data at Thread Level.

The native Multicast Label Distribution Protocol (mldp) model defines configuration and operational state data for the MLDP protocol.

See Native Data Model for MLDP.

The OpenConfig (OC) data models are defined by the OC community to create configuration and retreive operational state data of the network. This release introduces support for the following OC models:

• The OC Bidirectional Forwarding Detection data model, oc-bfd, defines the BFD protocol in multi-vendor environment to configure and get operational state data for the BFD protocol.

• The oc-platform data model supports streaming operational and configuration state data that are related to the underlying characteristics of the device.

See OpenConfig Data Models for Network Programmability Programmability Configuration Guide for Cisco NCS 5500 Series Routers.