Juniper JN0-280 Practice Test - Questions Answers, Page 7

Each port on a modern switch creates a separate collision domain. This allows multiple devices to communicate simultaneously without collisions on different ports.

Step-by-Step Breakdown:

Collision Domain:

A collision domain is a network segment where data packets can collide if two devices send packets simultaneously.

On a switch, each port creates a separate collision domain, so collisions only occur if two devices connected to the same port (through a hub, for instance) try to send data at the same time.

Switches vs Hubs:

Unlike hubs, which have one large collision domain, switches isolate collisions to individual ports, improving performance.

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Reference:

Switch Port Behavior: In Juniper switches, each port operates in its own collision domain, enhancing network efficiency by reducing the chances of packet collisions.

BGP (Border Gateway Protocol) has specific rules for route advertisement between peers.

Step-by-Step Breakdown:

EBGP to IBGP Route Propagation:

BGP peers advertise routes learned from EBGP peers to IBGP peers within the same AS. This ensures that routes learned from external networks are propagated internally within the AS.

IBGP to EBGP Route Propagation:

Routes learned from IBGP peers can be advertised to EBGP peers, but when advertising these routes, the router uses its own IP address as the next hop.

IBGP Split Horizon:

By default, IBGP peers do not advertise routes learned from one IBGP peer to another IBGP peer. This rule (IBGP split horizon) prevents routing loops within an AS.

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Reference:

BGP Advertisement Rules: Junos adheres to BGP standards, where IBGP peers do not propagate routes to other IBGP peers, but EBGP peers receive IBGP routes with the advertising router as the next hop.

When the discard option is configured as the next hop for a static route, it silently drops any packets that match the route without sending any notification to the sender.

Step-by-Step Breakdown:

Discard Behavior:

If a route uses the discard next hop, the router drops the packet without generating any ICMP message or error back to the sender. This is useful for creating null routes to prevent routing loops or blackhole traffic intentionally.

Reject vs. Discard:

The reject next hop, in contrast, drops the packet but sends an ICMP Destination Unreachable message back to the source.

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Reference:

Static Route Behavior: In Junos, the discard option ensures packets matching a static route are dropped silently, providing a way to discard traffic without alerting the source.

In a Virtual Chassis (VC) configuration, multiple Juniper switches are interconnected to form a single logical device. Each member switch in the Virtual Chassis plays a specific role.

Step-by-Step Breakdown:

Line Card Role:

Member switches acting as line cards provide additional ports for traffic forwarding but do not perform control or routing functions. These switches depend on the routing engine to handle control-plane tasks.

Routing Engine Role:

A switch in the routing-engine role is responsible for control-plane operations such as routing protocol management and control of the Virtual Chassis.

Virtual Chassis Roles:

Master Routing Engine: Handles control-plane functions and manages the entire Virtual Chassis.

Backup Routing Engine: Takes over if the master fails.

Line Card: Provides additional ports and handles data-plane operations.

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Reference:

Virtual Chassis: In a five-member Virtual Chassis, multiple switches act as line cards, while one or more switches are designated as the routing engines (master and backup).