JN0-280 Exam Dumps - Data Center, Associate (JNCIA-DC)

The exhibit shows a BGP peering scenario between three routers:router1androuter2are part of the same AS (AS65000), while theSP routeris in a different AS (AS65101). This indicates anEBGP (External BGP)peering between the SP router and router1, andIBGPbetween router1 androuter2.

Step-by-Step Breakdown:

Next-Hop Behavior in BGP:

IBGP: In IBGP, thenext-hop addressis not modified when advertising routes within the same AS. Thus, when router1 advertises routes learned from router2 to the SP router, it will keep thenext-hop addressof router1, not router2.

EBGP: In EBGP, thenext-hop addressis modified. When router1 receives routes from the SP router, it will advertise them to router2 with thenext-hop addressof router1.

Route Propagation:

Routes received byrouter1fromrouter2will be advertised to the SP router with router1 as the next hop.

Similarly, routes advertised by theSP routerwill be passed on to router2, with router1 remaining as the next hop.

Juniper Reference:

BGP Next-Hop: Juniper's BGP implementations follow standard BGP next-hop behavior, where the next-hop is modified in EBGP but not in IBGP, ensuring proper route advertisement across autonomous systems.

The configuration in the exhibit shows thepersistent-learningfeature enabled on interfacege-0/0/1.0.

Step-by-Step Breakdown:

Persistent Learning:

Persistent-learningensures that the MAC addresses learned on the interface are retained in theEthernet-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, enablingpersistent-learningensures that learned MAC addresses are not lost during reboots, contributing to smoother network operations in environments where stability is crucial.

Agenerated routein 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.