Juniper Updated JN0-280 Exam Questions and Answers by jayla

AnIP fabricis a network topology designed to provide a scalable, low-latency architecture that is typically implemented in modern data centers. It usesspine and leafswitches and enables efficienttraffic load sharingacross the network.

Step-by-Step Breakdown:

Spine-Leaf Architecture:

Leaf Devices: These switches connect to servers and edge devices within the data center. Each leaf switch connects to every spine switch.

Spine Devices: These high-performance switches interconnect all the leaf switches. There are no direct connections between leaf switches or spine switches. This architecture ensures that any two endpoints within the fabric are only one hop away from each other, minimizing latency.

Traffic Load Sharing:

An IP fabric leveragesEqual-Cost Multipath (ECMP)to distribute traffic evenly across all available paths between leaf and spine switches, providing effective load balancing. This ensures that no single link becomes a bottleneck and that traffic is distributed efficiently across the network.

Juniper Reference:

Juniper providesQFX Seriesswitches optimized for IP fabric topologies, allowing for scalable deployments in modern data centers.

EVPN-VXLAN: Often used in IP fabrics to extend Layer 2 services across the fabric with Layer 3 underlay, enabling both efficient routing and bridging.

Agenerated routein Junos OS is configured under the[edit routing-options]hierarchy.

Step-by-Step Breakdown:

Generated Routes:A generated route is created based on the presence of more specific routes in the routing table. It acts as a summary route and is generated when any of its contributing routes are active. This is commonly used to create aggregate routes in OSPF, BGP, or other protocols.

Configuration Hierarchy:The configuration for generated routes is placed under[edit routing-options], where other static and routing policies are also defined.

Command Example:

set routing-options generate route 10.10.0.0/16

Juniper Reference:

Routing Options: Juniper routers use the routing-options hierarchy to configure generated routes and other static routing behaviors.

When creating aLAG (Link Aggregation Group)in Junos, theduplex settingsandlink speedmust be the same across all member interfaces.

Step-by-Step Breakdown:

LAG Overview:A LAG combines multiple physical interfaces into a single logical interface to increase bandwidth and provide redundancy. All member links must act as a single cohesive unit.

Interface Requirements:

Duplex: All member interfaces must operate in the same duplex mode (either full-duplex or half-duplex). Mismatched duplex settings can cause performance issues, packet drops, or interface errors.

Link Speed: All interfaces in the LAG must have the same link speed (e.g., all interfaces must be 1 Gbps or 10 Gbps). Mismatched speeds would prevent the interfaces from functioning correctly within the LAG.

Configuration and Validation: Ensure that all member interfaces have identical settings before adding them to the LAG. These settings can be checked using the show interfaces command, and the LAG can be configured using:

set interfaces ae0 aggregated-ether-options link-speed 10g

set interfaces ge-0/0/1 ether-options 802.3ad ae0

Juniper Reference:

LAG Configuration: Duplex and link speed must be consistent across member interfaces to ensure proper LAG operation in Juniper devices.

In OSPF, routers exchange link-state information in different stages to establish full adjacency. TheMTU sizeis checked during theExchangestate.

Step-by-Step Breakdown:

OSPF Adjacency Process:

OSPF routers go through multiple stages when forming an adjacency:Down,Init,2-Way,ExStart,Exchange,Loading, andFull.

Exchange State:

During theExchangestate, OSPF routers exchangeDatabase Description (DBD)packets to describe their link-state databases. TheMTU sizeis checked at this stage to ensure both routers can successfully exchange these packets without fragmentation.

If there is anMTU mismatch, the routers may fail to proceed past the Exchange state.

Juniper Reference:

MTU Checking in OSPF: Junos uses the Exchange state to check for MTU mismatches, ensuring that routers can properly exchange database information without packet fragmentation issues.