Juniper JN0-364 問題集 練習問題・模擬試験｜日本語版＆英語版対応

Explanation: For Juniper platforms equipped with dual Routing Engines (REs), the fundamental technology required to provide high availability during a hardware or software failure of the primary RE is Graceful Routing Engine Switchover (GRES). According to Juniper Networks technical documentation, GRES allows the backup RE to stay in a "hot" standby state. When GRES is enabled, the primary RE synchronizes critical state information with the backup RE, specifically the chassis state and the interface state. This synchronization includes the Packet Forwarding Engine (PFE) configuration. When the primary RE fails, the backup RE takes over immediately. Because the PFE (which resides on the line cards) was already synchronized and is not restarted during the switchover, the router continues to forward packets that are already in flight or part of established flows. This prevents a complete network outage during an RE failover. Comparison with other options: NSB (Non-Stop Bridging - Option A): Focuses specifically on maintaining Layer 2 protocol states (like STP) during a switchover. LAG (Link Aggregation - Option B): Provides redundancy for physical links, not the control plane or the RE. BFD (Bidirectional Forwarding Detection - Option C): Is a protocol used for rapid detection of link or neighbor failures; it does not protect the RE or maintain forwarding during an internal switchover. It is important to note that while GRES maintains the forwarding state, it does not by itself maintain the routing protocol state (adjacencies). To keep OSPF or BGP sessions from dropping during the switchover, GRES must be paired with Non-Stop Active Routing (NSR). However, as the question focuses on the core requirement of continuing to forward packets, GRES is the foundational technology

Explanation: In Juniper Networks Junos OS, Generic Routing Encapsulation (GRE) and IP-in-IP (IP-IP) are common tunneling mechanisms used to transport packets across a network by encapsulating them within another protocol. Understanding the header structure and the limitations of these protocols is essential for proper MTU (Maximum Transmission Unit) management and security design. Overhead (Option A): Both GRE and IP-IP tunnels operate by adding an additional IP header to the original packet. An IP-IP tunnel (Protocol 4) adds a20-byteIPv4 header. A GRE tunnel (Protocol 47) adds the same20-bytedelivery IP header plus a minimum4-byteGRE header (totaling 24 bytes, which can increase if keys or sequencing are used). Because these headers are added to the payload, the total size of the packet increases. This "overhead" means that if the original packet was already at the MTU limit (e.g., 1500 bytes), the encapsulated packet will exceed it, potentially leading to fragmentation or the need to adjust the TCP MSS (Maximum Segment Size). Encryption (Option D): Crucially, according to Juniper Service Provider documentation, neither GRE nor IP-IP provides native encryption or data confidentiality. They are encapsulation protocols, not security protocols. The payload remains in cleartext and is visible to any device along the path. If security and encryption are required for data traversing these tunnels, they must be combined with IPsec (IP Security). While GRE is often used as the "carrier" for IPsec (to allow multicast or dynamic routing protocols which IPsec alone does not support), the GRE protocol itself remains an unencrypted delivery mechanism. Therefore, statements A and D accurately describe the architectural behavior of these tunnel types.

Explanation: Multiple Spanning Tree Protocol (MSTP), as defined in IEEE 802.1s and implemented in Juniper Networks Junos OS, allows for the grouping of VLANs into specific spanning tree instances. This provides significant scalability and load-balancing advantages over traditional STP or RSTP. To achieve this, switches must be grouped into logical "Regions." According to Juniper documentation, for two or more switches to be considered part of the same MSTP Region, they must possess an identical MSTP Configuration Identifier. This identifier consists of three specific attributes that must match exactly across all participating switches: MSTI Name (Region Name): A descriptive string (up to 32 characters) that identifies the region. MSTI Revision Level: A numerical value (0C65535) used to track configuration changes. VLAN-to-Instance Mapping: The specific table that defines which VLAN IDs are associated with which Multiple Spanning Tree Instances (MSTIs). If even one of these parameters―such as the Region name (Option A) ―differs, the switches will treat each other as being in separate regions. When switches are in different regions, they interact using the Common Spanning Tree (CST), effectively seeing the other region as a single "virtual bridge, " which limits the granularity of traffic engineering. The Extended system ID (Option B) is a component of the Bridge ID used to carry VLAN information in PVST+ but is not a region-matching requirement. Root bridge priority (Option C) and Root bridge ID (Option D) are variables used during the STP election process to determine the topology's root, but they do not define the boundaries of an MSTP region itself.