To determine the version of Cisco IOS XR Software packages installed on your router, log in to the router and enter the show install commit summary command

In a network where traffic has to be load balanced on two or more links, configuring equal metrics on the links would create Equal Cost Multipath (ECMP) next hops. Since the bandwidth of the links is not taken into consideration while load balancing, the higher bandwidth links are underutilized. To avoid this problem, you can configure Unequal Cost Multipath (UCMP), either locally (local UCMP), or natively (native UCMP) so that the higher bandwidth links carry traffic in proportion to the capacity of the links. UCMP supports IPv4 and IPv6 static VRF routes.

For more information, see the Configuring Unequal Cost Multipath for Static Routing: Example section in the http://www.cisco.com/c/en/us/td/docs/routers/crs/software/crs_r5-2/routing/configuration/guide/b_routing_cg52xcrs.html.

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.

In BFD, each end of the connection maintains a BFD state and transmits packets periodically over a forwarding path. Seamless BFD (SBFD) is unidirectional, resulting in faster session activation. The BFD state and client context is maintained on the head-end (initiator) only. The tail-end (reflector) validates the BFD packet and responds, so there’s no need to maintain the BFD state on the tail-end.

The autoroute destination feature allows you to automatically route traffic through a segment routing tunnel instead of manually configuring static routes. Static routes are always added with zero-cost metric, which can result in traffic that is mapped on multiple tunnels to always load-balance due to ECMP. This load-balancing may be undesirable when some of those tunnels have sub-optimal paths. With autoroute destination, only the tunnel whose IGP cost to its endpoint is lowest will be considered for carrying traffic.

Border gateway protocol link-state (BGP LS) is an Address Family Identifier (AFI) and Sub-address Family Identifier (SAFI) defined to carry interior gateway protocol (IGP) link-state database through BGP. BGP LS delivers network topology information to topology servers and Application Layer Traffic Optimization (ALTO) servers. BGP LS supports IS-IS and OSPFv2.

The Topology-Independent Loop-Free Alternate (TI-LFA) node protection functionality provides protection from node failures. The neighbor node is excluded during the post convergence backup path calculation.

The TI-LFA Shared Risk Link Groups (SRLG) protection functionality attempts to find the post-convergence backup path, which excludes the SRLGs of the protected link. All local links that share any SRLG with the protecting link are excluded during the post convergence backup path calculation.

For more information, see the .

Segment routing is a method of forwarding packets on the network based on the source routing paradigm. The source chooses a path and encodes it in the packet header as an ordered list of segments. Segments are an identifier for any type of instruction. For example, topology segments identify the next hop toward a destination. Each segment is identified by the segment ID (SID) consisting of a flat unsigned 32-bit integer.

Segment routing egress peer engineering (EPE) uses a controller to instruct an ingress provider edge or a content source within the segment routing domain to use a specific egress provider edge and a specific external interface to reach a destination. BGP peer SIDs are used to express source-routed inter-domain paths. Controllers learn BGP peer SIDs and the external topology of the egress border router through BGP-LS EPE routes. EPE functionality is only required at EPE egress border router and EPE controller.

MVPN IPv6 traffic can be carried over IPv4 GRE multicast tunnels using the standard GRE tunneling techniquethat is designed to provide the services to implement any standard point-to-point encapsulation scheme.

The named tunnel feature lets you name the TE tunnels in the network with unique tunnel IDs to be able to manage the network with more ease. This feature allows you to provision TE tunnels using STRING names.