Juniper Updated JN0-650 Exam Questions and Answers by julian

The show ospf interface output provides critical information about the local OSPF state.

Loopback Behavior (Option A): The output shows lo0.0 is in the DR (Designated Router) state with Nbrs 0. In Junos OS, OSPF adjacencies are not formed over loopback interfaces; they are treated as stub networks.

Neighbor State (Option D): Every interface listed (ge-0/0/1.0, ge-0/0/2.0, and lo0.0) shows Nbrs 0. This indicates that the router is not seeing any OSPF neighbors. Since the physical interfaces are in the DR state (meaning the router has elected itself as the DR because no other routers responded), it confirms the router is not receiving OSPF Hello messages from any potential neighbors on those segments.

Router ID: The DR ID 192.168.1.17 is the local router ' s own ID, not a neighbor it is trying to reach.

To secure a Layer 2 network running Multiple VLAN Registration Protocol (MVRP) against unauthorized VLAN propagation from rogue devices, you must control the registration state of the ports.

Forbidden Registration Mode (Option D): This mode is specifically designed to prevent an interface from participating in the MVRP exchange.

When a port is set to forbidden, it will neither register nor declare VLANs (except those statically configured on the interface).

If a rogue device sends MVRP PDUs to this interface, the distribution switch will ignore those PDUs, preventing the rogue device from dynamically creating or learning VLANs through that port.

Registration Hierarchy: In Junos OS 24.4, this is configured at the [edit protocols mvrp interface < interface-name > registration forbidden] level.

Other Modes: normal (default) allows full participation, while restricted ignores joins for VLANs not already statically defined on the switch but still declares its own.

Junos OS uses specific routing tables for handling multicast traffic to ensure loop prevention through Reverse Path Forwarding (RPF) checks:

Multicast RPF (Option C): The inet.0 table is the default unicast routing table. In most standard multicast deployments, Protocol Independent Multicast (PIM) performs its RPF checks against this table to determine the upstream interface toward the multicast source.

Topology Differences (Option A): The inet.2 table is specifically designed for multicast RPF lookups when the multicast forwarding topology differs from the unicast forwarding topology. This is common in environments using Multiprotocol BGP (MBGP) where you might want multicast traffic to follow a different path than standard data traffic.

inet.1 Role (Option B): The inet.1 table is the multicast forwarding cache. It stores (S,G) and (*,G) entries for actual packet forwarding. Routing protocols like MBGP or IS-IS do not place routes directly into inet.1; instead, PIM uses information from inet.0 or inet.2 to populate inet.1.

IS-IS and OSPFv3 (Option D): These protocols place their IPv4/IPv6 unicast routes into inet.0 or inet6.0. They do not place routes into inet.2 " directly " unless specific RIB-group configurations or address families are enabled to share those routes for multicast RPF purposes.

To interoperate with Cisco switches running Per-VLAN Spanning Tree Plus (PVST+), Juniper devices must use VLAN Spanning Tree Protocol (VSTP).

PVST+ Compatibility: VSTP is specifically designed to handle the per-VLAN BPDU requirements of Cisco ' s PVST+. It generates a separate spanning tree instance for each VLAN and uses the same multicast destination MAC address as Cisco devices.

Other Protocols: MSTP (B) is used for grouping VLANs into regions; RSTP (D) is a single-instance protocol (IEEE 802.1w) and is generally incompatible with per-VLAN BPDU requirements without additional configuration.