Juniper JN0-280 Exam Dumps

A generated route in 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.

OSPF (Open Shortest Path First) calculates the best path based on the cost of the route, which is derived from the bandwidth of the interfaces along the path.

Step-by-Step Breakdown:

OSPF Path Selection:

OSPF assigns a cost to each link, typically based on the link's bandwidth (higher bandwidth equals lower cost).

The OSPF algorithm computes the shortest path to a destination by adding the costs of all links in the path. The path with the numerically lowest total cost is chosen as the best path.

Cost Calculation:

The OSPF cost can be manually adjusted or automatically calculated using the default formula:

Cost=ReferenceBandwidthLinkBandwidth\text{Cost} = \frac{\text{Reference Bandwidth}}{\text{Link Bandwidth}}Cost=LinkBandwidthReferenceBandwidth

Juniper Reference:

OSPF Best Path Selection: OSPF selects the path with the lowest cumulative cost, ensuring efficient use of higher-bandwidth links in Junos networks.

The configuration in the exhibit shows the persistent-learning feature enabled on interface ge-0/0/1.0.

Step-by-Step Breakdown:

Persistent Learning:

Persistent-learning ensures that the MAC addresses learned on the interface are retained in the Ethernet-switching table, even after a device reboot. This prevents the need to re-learn MAC addresses after the device restarts, improving stability and reducing downtime.

Use Case:

This feature is particularly useful in environments where the re-learning of MAC addresses could cause temporary disruptions or delays in communication, such as in critical Layer 2 network segments.

Command Example:

set switch-options interface ge-0/0/1.0 persistent-learning

Juniper Reference:

Persistent MAC Learning: In Junos, enabling persistent-learning ensures that learned MAC addresses are not lost during reboots, contributing to smoother network operations in environments where stability is crucial.

In the exhibit, R2 receives the same OSPF update from both R1 and R3. OSPF has mechanisms to prevent unnecessary processing of duplicate LSAs (Link-State Advertisements).

Step-by-Step Breakdown:

OSPF LSA Processing:

OSPF uses LSAs to exchange link-state information between routers. When a router receives an LSA, it checks if it already has a copy of the LSA in its Link-State Database (LSDB).

Duplicate LSAs:

If R2 has already received and processed the update from R1, it will ignore the update from R3 because it already has the same LSA in its database. OSPF uses the concept of flooding, but it does not reprocess LSAs that it already knows about.

R2 Behavior:

R2 will keep the update from R1 (the first one it received) and will ignore the same LSA from R3, as it is already in the LSDB.

Juniper Reference:

OSPF LSA Processing: Junos adheres to OSPF standards, ensuring that duplicate LSAs are not processed multiple times to avoid unnecessary recalculations.

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.