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

AMAC address of FF-FF-FF-FF-FF-FFis the Ethernetbroadcast address. When a switch receives a frame with this destination MAC address, it is required to forward the frame to all interfaces except the one it was received on.

Step-by-Step Breakdown:

Broadcast Frame Handling:When a frame with the broadcast MAC address is received, the switch will flood it out of all active ports that belong to the same VLAN as the incoming frame. The broadcast frame is not sent back out of the ingress interface (the interface where the frame was originally received).

Purpose of Flooding:Broadcasting is used to ensure that the frame reaches all devices within the broadcast domain (all devices within the same VLAN), which may not have a specific entry for the MAC address in their MAC address table.

Juniper Reference:

Layer 2 Frame Forwarding: Juniper switches flood broadcast frames to all ports in the same VLAN, except the port the frame was received on.

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.

In the exhibit, the BGP routes are marked ashidden. This typically happens when the routes are not considered valid for use, but they remain in the routing table for reference. One common reason for BGP routes being hidden is that thenext hopfor these routes is unreachable.

Step-by-Step Breakdown:

BGP Next Hop:In BGP, when a route is received from a neighbor, thenext hopis the IP address that must be reachable for the route to be used. If the next hop is unreachable (i.e., the router cannot find a path to the next-hop IP), the route is marked as hidden.

Analyzing the Exhibit:The exhibit shows that the BGP next hop for all hidden routes is 10.4.4.4. If this IP is unreachable, the BGP routes from that neighbor will not be considered valid, even though they appear in the routing table.

Verification:

Use the command show route 10.4.4.4 to check if the next-hop IP is reachable.

If the next-hop is not reachable, the BGP routes will be hidden. Resolving the next-hop reachability issue (e.g., fixing an IGP route or an interface) will allow the BGP routes to become active.

Juniper Reference:

Junos Command: show route hidden displays routes that are not considered for forwarding.

Troubleshooting: Check the next hop reachability for hidden BGP routes using show route .