4A0-D01: Nokia Data Center Fabric FundamentalsDemo

A configured next-hop group can be referenced by multiple static routes. SR Linux next-hop groups can contain one or more next hops, and referenced static routes use the group’s forwarding or blackhole behavior.

A MAC entry of type duplicate is created when the MAC moves across interfaces more times than the configured threshold during the configured monitoring window. The duplicate entry retains a learned destination, but that destination does not make the MAC a statically configured MAC on the interface. Static MACs are a separate bridge-table entry type.

BGP does not automatically discover neighboring BGP speakers. Peering is established through explicit configuration, including the neighbor address and autonomous system details. Its maturity, dual IPv4/IPv6 support, and scalable control-plane characteristics are valid reasons it is commonly used in data-center networks.

Leaf routers normally peer with spine routers, not directly with other leaf routers. Locally connected server prefixes are advertised from each leaf to the spines, and the spines re-advertise those routes to other leaves; thus, remote server prefixes are learned through the spine layer.

An IRB interface associates a MAC-VRF with an IP-VRF locally on the same SR Linux router, enabling integrated Layer 2 bridging and Layer 3 routing (including inter-subnet forwarding).

Fabric Services System uses declarative fabric intent data to describe the desired fabric topology and generate the participating nodes’ configuration files for deployment. A YAML topology file can provide the nodes, links, and device-profile data used as the basis for a fabric intent. The Digital Sandbox is a simulator for evaluating a prospective design, not the mechanism that generates production configuration files; telemetry supports monitoring rather than initial configuration generation.

The SR Linux management server manages application YANG models and translates them into protobufs for the IDB. The application manager instead manages application lifecycle activities, including reading application configuration, starting applications, and monitoring and restarting failed application processes.

SR Linux uses a mainline, unmodified Linux kernel; modular applications with model-driven state; and the NetOps Development Kit (NDK) for integrated agents. Its documented management interfaces are the CLI, gNMI, and JSON-RPC via gRPC, rather than SNMP for CLI access.

SR Linux implements routing functions as separate modular, lightweight applications; each protocol, such as BGP or IS-IS, runs in its own application rather than all routing protocols running in a single Linux application. Each application uses a YANG model for configuration and state, while the IDB supports publish/subscribe information exchange between applications. Third-party applications can also integrate with SR Linux.

A private candidate allows its user to commit that user’s changes. The ! prompt flag indicates that the baseline configuration is not synchronized with the running configuration, such as after another user commits changes. baseline diff is used to review those baseline-versus-running differences; it is not required because the user cannot commit.

The asymmetric forwarding model requires every leaf to configure the source and destination VLANs and their corresponding VNIs, including VLANs for which that leaf has no local hosts. Symmetric IRB instead uses a Layer 3 transit VNI between VTEPs and does not impose that all MAC-VRFs be instantiated on every leaf regardless of local host attachment. In symmetric IRB, both ingress and egress VTEPs perform routing and bridging; in asymmetric IRB, the egress VTEP only bridges traffic to the destination VLAN.

The static-routes container defines destination-prefix route entries, their preference, and the referenced next-hop group. A blackhole action is configured within the referenced next-hop group under next-hop-groups, rather than within static-routes.

Checkpoint numbering uses the lowest number for the most recently saved checkpoint. When the checkpoint limit is exceeded, the oldest checkpoint is removed and the remaining checkpoints are incremented, so checkpoint 0 is not always the oldest. Checkpoints store the complete configuration as JSON files, can be used to revert the running configuration, and can be created after successful commits.

A system-cpu-policer is implemented in CPM software and applies an aggregate rate limit to terminating traffic received from all line cards. The distributed-policer is the hardware-based policer on the ingress line card; both policer types can be used in the same CPM-filter entry.

Nokia EDA is an open, cloud-native, microservices-based automation framework built on Kubernetes. It supports declarative fabric intent and can generate and deploy fabric configuration, provides a Digital Sandbox that emulates a digital twin of the data-center fabric, and integrates with cloud-management platforms through its Connect service. Therefore, describing it as built on an existing proprietary network-automation platform is false.

BGP selects the path with the higher local-preference value. Applying an import policy to routes received from peer 10.1.1.0 and setting local preference to 200 makes the matching 192.168.201.0/30 path through Spine-1 preferred over the default value of 100. Export policy does not affect Leaf-1’s selection of a received route.

Nokia SR Linux supports Linux users, local SR Linux users, and remote users. It does not define container users as a supported user type.

The AS_PATH attribute records the autonomous systems a route advertisement has traversed. BGP uses it for loop detection and as a route-selection attribute. A BGP router is uniquely identified by its BGP identifier (router ID), not by the AS_PATH attribute.

A modern leaf-spine Clos fabric uses a routed Layer 3 underlay, and Equal-Cost Multipath (ECMP) distributes flows over the available spine paths. It is not defined by combining Layer 2 switches with Layer 3 routers to distribute traffic. Adding spines increases aggregate uplink capacity, and super-spine tiers can interconnect larger leaf-spine pods or clusters.

Day 2+ activities occur after initial deployment and include telemetry monitoring, state monitoring, and subsequent fabric reconfiguration. Creating and validating fabric design templates through a fabric intent belongs to the pre-deployment planning and design lifecycle, which Nokia classifies as Day 0.

Nokia EDA’s Digital Sandbox is a containerized virtual infrastructure that creates a digital twin of the production data-center fabric. It is used to test and validate planned network changes before they are deployed to production, reducing deployment risk.

ZTP obtains the provisioning-script location from DHCP and then uses that script to locate provisioning artifacts. Failures can occur when DHCP does not provide the required provisioning information, when the provisioning script cannot be downloaded, or when downloaded files cannot be copied to storage. A DHCP server address is not a required item within the provisioning script.

The static route has two equal-cost next hops, via ethernet-1/1.0 and ethernet-1/2.0. ECMP path selection is hash-based; the displayed Resilient hash: false status means resilient hashing is not enabled, not that round-robin selection is used.

SR Linux uses the route with the lowest preference value when multiple protocols provide the same prefix; lower numerical values indicate greater preference. Therefore, a route with the highest preference value is not selected. Equal-preference routes from the same protocol use the lowest metric, and equal-cost paths can support ECMP.