Juniper JN0-280 Practice Test - Questions Answers, Page 3

EVPN (Ethernet Virtual Private Network) is a standard protocol used for building Layer 2 and Layer 3 VPNs over an IP or MPLS network. The signaling protocol used for EVPN is BGP (Border Gateway Protocol).

Step-by-Step Breakdown:

BGP as the EVPN Signaling Protocol:

EVPN uses BGP to exchange MAC address reachability information between routers (PE devices). This enables devices to learn which MAC addresses are reachable through which PE devices, facilitating Layer 2 forwarding across an IP or MPLS core.

BGP Extensions for EVPN:

BGP is extended with new address families (e.g., EVPN NLRI) to carry both MAC and IP address information, allowing for scalable and efficient multi-tenant network solutions.

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Junos EVPN Configuration: Juniper uses BGP as the control plane for EVPN to exchange MAC and IP route information between different data center devices.

To display the mapping between VLAN IDs and ports on a Juniper switch, the show vlans command is used.

Step-by-Step Breakdown:

VLAN Information:

The show vlans command displays detailed information about VLAN configurations, including the VLAN ID, associated interfaces (ports), and VLAN membership.

Command Example:

show vlans

This command will provide an output listing each VLAN, its ID, and the interfaces associated with the VLAN, enabling network engineers to quickly verify VLAN to port mappings.

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VLAN Verification: Use the show vlans command to verify which VLANs are configured on the switch and the ports that are members of those VLANs.

To verify that your router is learning routes from a remote BGP peer at a specific IP address (e.g., 10.10.100.1), the correct command to use is show route receive-protocol bgp.

Step-by-Step Breakdown:

BGP Route Learning:

The show route receive-protocol bgp command displays the routes that have been received from a specified BGP peer. This helps in confirming that the remote peer is sending routes correctly and that your router is receiving them.

Command Example:

show route receive-protocol bgp 10.10.100.1

This will show all routes that have been received from the BGP peer with IP address 10.10.100.1.

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BGP Route Verification: Use this command to troubleshoot and verify that routes from a specific BGP peer are being received.

When a MAC limiting violation occurs on a Juniper switch, the switch will perform the following actions by default:

Step-by-Step Breakdown:

Port Disabled:

When the number of MAC addresses on an interface exceeds the configured limit, the port is automatically disabled to prevent further violations. This is a protective mechanism to prevent MAC address flooding.

Packet Dropped:

Additionally, packets from the violating MAC address are dropped to prevent any further communication from that address. This ensures that only valid MAC addresses are allowed to communicate through the interface.

Example Configuration:

set ethernet-switching-options secure-access-port interface <interface-name> mac-limit 5

If more than five MAC addresses are learned, the port is disabled, and excess packets are dropped.

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MAC Limiting: When the switch detects a MAC limiting violation, it disables the port and drops further packets from the violating MAC addresses to maintain network security.

The source MAC address in the Ethernet header is used to populate the bridging table (also called the MAC address table) on a switch. When a frame arrives at a switch, the switch examines the source MAC address and records it along with the ingress port in its MAC address table.

Step-by-Step Breakdown:

Learning Process:

When an Ethernet frame arrives on a switch port, the switch looks at the source MAC address and adds this MAC address to the MAC table along with the port it was received on. This process is called MAC learning.

Purpose:

The switch uses this information to determine the correct port to send frames destined for that MAC address in future transmissions, thus ensuring efficient Layer 2 forwarding.

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Ethernet Switching: Juniper switches use source MAC addresses to build and maintain the MAC address table, which is essential for Layer 2 switching.

When configuring an aggregate route, you have options for how to handle traffic that matches the route but does not match any more specific route in the routing table. Two actions can be taken: discard and reject.

Step-by-Step Breakdown:

Discard:

The discard option will silently drop packets that match the aggregate route. No notification is sent to the sender, and the packet is simply dropped.

Reject:

The reject option will drop the packet and also send an ICMP Destination Unreachable message back to the sender. This informs the sender that the packet could not be delivered because there is no specific route available.

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Aggregate Routes: The reject and discard next-hop options provide different levels of feedback when packets cannot be routed, and they can be used to control how unreachable destinations are handled.

An IP fabric is a network architecture commonly used in data centers to provide scalable, high-throughput connectivity using a spine-leaf topology.

Step-by-Step Breakdown:

Layer 3 Routing Protocol:

An IP fabric relies on a Layer 3 routing protocol, typically BGP or OSPF, to provide routing between the leaf and spine switches. This ensures efficient traffic forwarding across the network.

Single Connection Between Spine and Leaf:

In an IP fabric, each leaf switch connects to every spine switch with a single connection. This ensures that traffic between any two leaf switches can travel through the spine layer in just two hops.

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Spine-Leaf Design: Juniper's IP fabric implementations are designed for scalability and low-latency routing, often using protocols like BGP for Layer 3 control.

Bidirectional Forwarding Detection (BFD) is a network protocol used to detect failures in the network path between two devices quickly.

Step-by-Step Breakdown:

Path Failure Detection:

BFD provides a low-overhead mechanism for detecting failures in forwarding paths across Layer 3 networks. It is much faster than traditional routing protocol timers and can detect failures within milliseconds.

BFD in Routing:

BFD can be integrated with routing protocols like OSPF, BGP, or IS-IS to trigger a faster convergence when a network path goes down.

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BFD Configuration: Juniper devices use BFD to monitor network paths and ensure fast failure detection, enhancing network resilience.

Per-flow load balancing ensures that packets within the same flow are always forwarded over the same path, ensuring that packet order is preserved.

Step-by-Step Breakdown:

Flow Definition:

A flow is typically defined by a combination of packet attributes like source/destination IP, source/destination port, and protocol type. Packets that belong to the same flow are routed over the same path to avoid reordering.

Per-Flow Behavior:

In per-flow load balancing, the hashing algorithm ensures that all packets in a particular flow use the same egress port, maintaining order across the network.

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Load Balancing in Juniper: This method ensures that flows are balanced across multiple paths while preventing packet reordering within a single flow.