Juniper JN0-280 Data Center, Associate JNCIA-DC Exam Practice Test

Answer : D

To configure aggregated Ethernet (AE) interfaces on a Junos device, the configuration is done under the [edit chassis] hierarchy.

Step-by-Step Breakdown:

Chassis Configuration:

The chassis configuration is responsible for enabling the hardware to support Link Aggregation Groups (LAGs), allowing multiple physical interfaces to be bundled into a single logical interface for load balancing and redundancy.

Command Example:

set chassis aggregated-devices ethernet device-count <number>

This command enables a specific number of aggregated Ethernet interfaces on the device.

Juniper Reference:

LAG Configuration in Junos: The chassis hierarchy is used to allocate and manage hardware resources for aggregated Ethernet interfaces in Juniper devices.

Answer : D

An IRB (Integrated Routing and Bridging) interface provides routing functionality between VLANs at Layer 3, allowing devices in different VLANs to communicate with each other.

Step-by-Step Breakdown:

IRB Functionality:

The IRB interface enables routing between different VLANs by acting as a Layer 3 gateway. Traffic within the same VLAN is handled by Layer 2 switching, while traffic between VLANs is routed through the IRB interface.

Layer 3 Routing Between VLANs:

Each VLAN can be assigned an IP address on the IRB interface, which allows traffic to flow between VLANs based on Layer 3 IP routing.

Juniper Reference:

IRB Interface Configuration: Juniper supports IRB for inter-VLAN routing on devices like the EX and QFX series switches, facilitating Layer 3 communication in data centers.

Answer : B

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.

Juniper Reference:

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

Answer : C, D

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.

Juniper Reference:

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.

Answer : A

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.

Juniper Reference:

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

Answer : A, C, E

Filter-Based Forwarding (FBF) in Junos OS allows traffic to be routed based on specific criteria such as source address, rather than just the destination address. This is useful in scenarios like policy routing or providing multiple paths for different types of traffic.

Step-by-Step Breakdown:

Instance-Type Forwarding:

You must create an instance-type forwarding routing instance. This routing instance allows for different routing tables based on the incoming packet filter.

Command:

set routing-instances FBF-instance instance-type forwarding

Match Filter:

You need to create a filter to match the traffic that will be forwarded according to your custom routing policy. This filter is applied to an interface to determine which traffic will use the custom forwarding instance.

Command Example:

set firewall family inet filter FBF-filter term 1 from source-address

Answer : B

When creating a LAG (Link Aggregation Group) in Junos, the duplex settings and link speed must 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.