Most Recent Juniper JN0-281 Exam Dumps

In Junos, static routes are eligible to be exported into dynamic routing protocols if you configure an export policy that matches them. For management-only routes, especially default routes or specific management subnets used for out-of-band access, you often want to ensure they never leak into the production routing domain. The no-readvertise parameter is designed for this purpose. When you mark a static route as no-readvertise, Junos flags it so other routing protocols do not export or readvertise it, even if an export policy would otherwise match it. This helps keep the management plane isolated from the data plane and prevents accidental propagation of management reachability into the fabric underlay or overlay.

The reject and discard options control how packets are handled if they match the route, not whether the route is eligible to be exported. Preference 255 changes the route's selection priority relative to other routes, but it does not prevent export. Therefore, no-readvertise is the correct configuration knob when the explicit goal is to prevent propagation of a management static route to other routers.

On broadcast network types in OSPF, such as Ethernet segments, forming a full mesh of adjacencies between every pair of routers would create significant control-plane overhead. Every router would need to maintain neighbor state with every other router, exchange database information redundantly, and flood link-state updates across many parallel adjacencies. This becomes inefficient as the number of routers on the segment grows.

To address this, OSPF elects a Designated Router and a Backup Designated Router. The DR acts as the central point for adjacency formation on that broadcast segment. Instead of each router forming full adjacencies with all others, routers form full adjacencies primarily with the DR and BDR. The DR is responsible for generating and flooding network LSAs that represent the broadcast segment and for coordinating reliable LSA flooding on that segment. This significantly reduces the number of adjacencies and the volume of duplicated database exchange and LSA flooding, which is why option A is correct.

The BDR is a standby control-plane role. It monitors the segment and is prepared to take over the DR function if the DR fails, improving stability and convergence. However, the primary purpose of having DR and BDR is the scaling benefit of reduced adjacency and flooding overhead on broadcast networks.

In Junos Ethernet switching, a trunk interface is intended to carry multiple VLANs using 802.1Q tags. The native VLAN ID feature defines how the trunk handles frames that arrive without an 802.1Q tag and how it can transmit untagged frames when required. When a native VLAN is configured on a trunk, untagged inbound frames are mapped into the native VLAN's Layer 2 broadcast domain. Likewise, traffic belonging to the native VLAN can be sent untagged on that trunk, depending on how the receiving device expects to process untagged frames. This is commonly used in data center environments to interoperate with devices that require one VLAN to be carried untagged, or for specific control-plane or legacy connectivity requirements.

Option A is incorrect because native VLAN does not restrict the trunk to tagged-only traffic; it explicitly provides a mechanism to accept or emit untagged frames on a trunk. Option B is incorrect because access ports are designed for a single VLAN and normally treat traffic as untagged by default; they do not become ''tagged access'' by using native VLAN. Option C is incorrect because native VLAN does not change the VLAN ID range; VLAN ID ranges are determined by the 802.1Q standard and platform support, not by the native VLAN feature.

In modern data center architectures, an overlay network is a logical or virtual network built on top of an underlay, where the underlay is the physical IP fabric that provides basic Layer 3 transport and reachability between fabric nodes. The overlay abstracts the physical topology and delivers tenant connectivity and segmentation services. This makes the statement that an overlay is a virtual network running on top of a physical network correct.

In EVPN VXLAN based data centers, overlays commonly carry both Layer 2 and Layer 3 services. Layer 2 extension is achieved by encapsulating Ethernet frames inside VXLAN so that a VLAN like segment can span multiple leaf switches across a routed underlay. Layer 3 services are delivered either through symmetric routing at the VTEPs or by advertising IP prefixes and host routes through the overlay control plane. As a result, overlays are not limited to Layer 3 traffic only, and statement D is correct.

The overlay is not defined by being public versus private. It can be built for private multi tenant segmentation inside a single data center, across multiple data centers, or to connect to external services, but public network is not a defining attribute.

Verification sources from Juniper documentation

https://www.juniper.net/documentation/us/en/software/junos/evpn-vxlan/topics/topic-map/evpn-vxlan-overview.html

https://www.juniper.net/documentation/us/en/software/junos/vxlan/topics/topic-map/vxlan-overview.html

On Junos Ethernet switching, access and trunk ports serve different purposes and therefore treat VLAN tags differently by default. An access port is intended for a single VLAN and is designed to connect to endpoints that do not tag their frames. Because of that, access ports forward traffic as untagged on the wire and internally associate those untagged frames to the configured access VLAN. This makes access ports the standard choice for single-VLAN server NICs, management devices, and any endpoint expecting a plain Ethernet connection.

A trunk port is intended to carry traffic for multiple VLANs over a single link, which is typical for switch-to-switch uplinks, leaf-to-spine connectivity where VLAN services are extended, and hosts or appliances that use VLAN tagging. By default, trunk ports forward tagged traffic and require VLAN tags to identify the VLAN membership of each frame. Untagged behavior on a trunk is not assumed by default and is typically governed by configuring a native VLAN or equivalent untagged VLAN handling, depending on platform and design. Without such configuration, untagged frames are not treated as a normal expected case for a trunk link in data center fabrics.

Therefore, the correct default statements are that access ports forward untagged traffic and trunk ports forward tagged traffic, matching options B and D.