JN0-280: Data Center, Associate
Juniper
Exam Number: JN0-280
Exam Name: Data Center, Associate
Length of test: 90 mins
Exam Format: Multiple-choice, Drag and Drop, and HOTSPOT questions.
Exam Language: English
Number of questions in the actual exam: 65 questions
Passing Score: 70%
Topics Covered:
-
Junos OS Fundamentals
-
Configuration and Management
-
Routing Fundamentals
-
Interface and VLAN Configuration
-
Security and Firewall Filters
-
Troubleshooting and Monitoring
This study guide should help you understand what to expect on the JN0-280 exam and includes a summary of the topics the exam might cover and links to additional resources. The information and materials in this document should help you focus your studies as you prepare for the exam.
Related questions
What are two device roles in a five-member Virtual Chassis? (Choose two.)
You are creating an IP fabric underlay and want to use OSPF as your routing protocol.
In this scenario, which statement is correct?
You want to minimize topology disruptions in your network when the rpd process restarts on a device. Which service would accomplish this task?
Bidirectional Forwarding Detection (BFD)
link aggregation groups
graceful restart (GR)
Virtual Chassis
Explanation:
Graceful Restart (GR) is a feature that allows a router to maintain forwarding even when the routing process (e.g., the rpd process in Junos) is restarting, minimizing disruption to the network.
Step-by-Step Breakdown:
Graceful Restart Function:
During a GR event, the forwarding plane continues to forward packets based on existing routes, while the control plane (rpd process) is restarting. This prevents traffic loss and maintains routing stability.
Minimizing Disruptions:
GR is particularly useful in ensuring continuous packet forwarding during software upgrades or routing protocol process restarts.
Juniper
Reference:
Graceful Restart in Junos: GR ensures high availability by maintaining forwarding continuity during control plane restarts, enhancing network reliability.
You are configuring an aggregate route. In this scenario, which two statements are correct? (Choose two.)
Reject will silently drop the traffic.
Discard will silently drop the traffic.
Reject will send an ICMP Destination Unreachable message back to the sender.
Discard will send an ICMP Destination Unreachable message back to the sender.
Explanation:
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.
Juniper
Reference:
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.
What is the primary purpose of an IRB Layer 3 interface?
to provide load balancing
to provide a default VLAN ID
to provide inter-VLAN routing
to provide port security
Explanation:
The primary purpose of an IRB (Integrated Routing and Bridging) interface is to enable inter-VLAN routing in a Layer 3 environment. An IRB interface in Junos combines the functionality of both Layer 2 bridging (switching) and Layer 3 routing, allowing devices in different VLANs to communicate with each other.
Step-by-Step Breakdown:
VLANs and Layer 2 Switching:
Devices within the same VLAN can communicate directly through Layer 2 switching. However, communication between devices in different VLANs requires Layer 3 routing.
IRB Interface for Inter-VLAN Routing:
The IRB interface provides a Layer 3 gateway for each VLAN, enabling routing between VLANs. Without an IRB interface, devices in different VLANs would not be able to communicate.
Configuration:
In Juniper devices, the IRB interface is configured by assigning Layer 3 IP addresses to it. These IP addresses serve as the default gateway for devices in different VLANs.
Example configuration:
set interfaces irb unit 0 family inet address 192.168.1.1/24
set vlans vlan-10 l3-interface irb.0
This allows VLAN 10 to use the IRB interface for routing.
Juniper
Reference:
IRB Use Case: Inter-VLAN routing is essential in data centers where multiple VLANs are deployed, and Juniper's EX and QFX series switches support IRB configurations for this purpose.
Which statement is correct about aggregate routes?
The default next hop is discard.
The default next hop is readvertise.
The default next hop is resolve.
The default next hop is reject.
Explanation:
An aggregate route is a summarized route that is created by combining multiple specific routes into a single, broader route. In Junos OS, when an aggregate route is configured, its default next hop is set to reject.
Step-by-Step Explanation:
Aggregate Route:
Aggregate routes are used to reduce the size of routing tables by representing a collection of more specific routes with a single summary route. They help improve routing efficiency and scalability, especially in large networks.
Default Next Hop Behavior:
When you configure an aggregate route in Junos OS, it has a reject next hop by default.
The reject next hop means that if a packet matches the aggregate route but there is no more specific route in the routing table for that destination, the packet will be discarded, and an ICMP 'destination unreachable' message is sent to the source.
This behavior helps to prevent routing loops and ensures that traffic isn't forwarded to destinations for which there is no valid route.
Modifying Next Hop:
If needed, the next hop behavior of an aggregate route can be changed to discard (which silently drops the packet) or to another specific next hop. However, by default, the next hop is set to reject.
Juniper
Reference:
Junos Command: set routing-options aggregate route <route> reject to configure an aggregate route with a reject next hop.
Verification: Use show route to verify the presence and behavior of aggregate routes.
When troubleshooting an OSPF neighborship, you notice that the router stopped at the ExStart state. What is the cause of this result?
The priority is set to 255.
There is an interval timing mismatch.
There is an area ID mismatch.
There is an MTU mismatch.
Explanation:
When an OSPF (Open Shortest Path First) neighborship is stuck in the ExStart state, it usually points to a mismatch in Maximum Transmission Unit (MTU) settings between two routers trying to establish the adjacency. The ExStart state is where OSPF routers negotiate the master-slave relationship and exchange DBD (Database Description) packets.
Step-by-Step Breakdown:
OSPF Neighbor States: OSPF goes through several states to establish an adjacency with a neighbor:
Down: No hello packets have been received.
Init: Hello packets are received, but bidirectional communication isn't confirmed.
2-Way: Bidirectional communication is established.
ExStart: The routers are negotiating who will be the master and who will be the slave, and begin to exchange DBD packets.
Exchange: The routers start exchanging the database information.
Loading: The routers process the Link-State Advertisements (LSAs).
Full: The adjacency is fully established.
MTU Mismatch Issue:
During the ExStart state, both OSPF routers must agree on their MTU values. If there is an MTU mismatch between the two routers, OSPF neighbors will fail to move from the ExStart to the Exchange state. The router with the larger MTU setting will not accept DBD packets from the router with a smaller MTU because the packets may exceed the smaller MTU size.
In Juniper devices, this behavior can be identified by examining the MTU settings using the show interfaces command and ensuring both routers have matching MTU configurations. To resolve this issue, either match the MTU settings on both routers or configure OSPF to ignore MTU mismatches using the command set protocols ospf ignore-mtu.
Juniper
Reference:
Junos Command: show ospf neighbor helps diagnose neighbor states.
MTU Adjustment: set interfaces <interface-name> mtu <size> can be used to set the MTU values correctly.
Exhibit:
How many stages are shown in the exhibit?
2
5
6
3
Explanation:
The exhibit shows a Folded IP Clos Architecture, which is also referred to as a 3-stage Clos network design. This architecture typically consists of two layers of switches:
Spine Layer: The top row of switches.
Leaf Layer: The bottom row of switches.
Step-by-Step Breakdown:
Clos Architecture:
A 3-stage Clos network has two types of devices: spine and leaf. In this design, each leaf switch connects to every spine switch, providing a high level of redundancy and load balancing.
Stage Explanation:
Stage 1: The first set of leaf switches.
Stage 2: The spine switches.
Stage 3: The second set of leaf switches.
The Folded Clos architecture shown here effectively 'folds' the 3-stage design by combining the ingress and egress leaf layers into one, reducing it to two visible layers, but still maintaining the overall 3-stage architecture.
Juniper
Reference:
IP Clos Architecture: The 3-stage Clos design is commonly used in modern data centers for high availability, redundancy, and scalability.
Exhibit:
Referring to the exhibit, which behavior does this configuration enable on the ge-0/0/1.0 interface?
Which signaling protocol is used for EVPN?
OSPF
PIM
IS-IS
BGP
Explanation:
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.
Juniper
Reference:
Junos EVPN Configuration: Juniper uses BGP as the control plane for EVPN to exchange MAC and IP route information between different data center devices.
Question