Nokia Data Center Fabric Fundamentals Free Sample Questions

Bidirectional Forwarding Detection (BFD) is a low-overhead, short-duration protocol designed to provide very fast failure detection for various routing protocols, including BGP. It operates independently of the routing protocol's own timers, allowing for sub-second detection of link or node failures, which then signals BGP to tear down the session and reconverge much faster than relying on BGP's slower keepalive and hold timers. STP is a Layer 2 protocol used to prevent loops and is not used in a Layer 3 leaf-spine fabric. LACP is used for link aggregation. OSPF is another routing protocol and would not be used to monitor an eBGP session.

In the SR Linux architecture, the Management Server is the central component that handles configuration transactions. When a configuration is committed via an interface like the CLI or gNMI, the Management Server validates it against the YANG models and then translates it into the protobuf format that the IDB uses. The IDB then notifies the relevant applications (like the BGP application) of the state change. The Application Manager is responsible for the lifecycle of applications, not configuration translation.

IP-VRF (Virtual Routing and Forwarding) is the standard technology used to create multiple, independent routing table instances within a single physical router. This allows for complete Layer 3 isolation between tenants, preventing traffic from one customer's network from being routed to another's. MAC-VRF is used for Layer 2 segmentation, while subinterfaces are used to logically divide a physical interface but do not provide routing table isolation on their own.

Zero Touch Provisioning (ZTP) is an automated process that enables a network device to provision itself without manual CLI commands. Typically, the device sends a DHCP request on its management port, and the DHCP server responds with options that provide the location of a bootstrap configuration script and the final software image, allowing the device to configure itself and join the network automatically.

In a leaf-spine (or Clos) topology, the rule is that leaf switches connect only to spine switches, and spine switches connect only to leaf switches. There are no direct connections between leaf switches or between spine switches. All traffic between leaves, including east-west traffic, traverses a spine switch, ensuring a consistent and predictable number of hops (always two: leaf-spine-leaf).

To send logs to a remote server, the server's IP address and transport parameters (like UDP or TCP) must be defined as a destination.

A rule is needed to match the desired log messages (based on severity, application, etc.) and associate them with the action of sending them to the configured remote destination.

To check the specific status and configuration of a subinterface, you must specify its full name, which includes the physical port and the subinterface index (e.g., ethernet-1/1.100). This command will display detailed information for that logical interface, including its operational state, associated VLAN, IP address, and network instance, which is crucial for troubleshooting.

Even with multiple equal-cost paths available, ECMP relies on a hashing algorithm to distribute traffic. A typical default hash uses Layer 3/4 headers (source/destination IP, source/destination port). For a single, long-lived TCP session between two endpoints, these values are constant. Therefore, the hash calculation will always produce the same result, sending all packets for that specific flow down the same path. This is expected behavior known as per-flow load balancing. To see traffic use multiple paths, multiple independent flows with different header information are required.

The top command in the SR Linux CLI is a shortcut that immediately returns the user to the root of the current mode's hierarchy. If in configuration mode, it goes to /configure; if in operational mode, it goes to /. The .. command only moves up one level in the hierarchy, and exit all would exit the configuration mode entirely, not just go to the top.

A MAC-VRF defines a Layer 2 forwarding domain, essentially a virtual switch. Associating a subinterface (which is typically tied to a VLAN) with a MAC-VRF tells the system that any traffic received on that subinterface belongs to that specific L2 VPN segment. This is the logical binding between the physical/virtual port and the L2 service instance. A Layer 3 gateway (IRB interface) would be associated with an IP-VRF.