JNCIS-ENT · domain
High Availability
Practise Juniper Networks Enterprise Routing and Switching, Specialist (JNCIS-ENT, JN0-352) (JNCIS-ENT) High Availability practice questions — original exam-style scenarios with answer choices, explanations, and analysis of common mistakes.
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What to know about High Availability
High Availability questions test whether you can apply the concept in context, not just recognise a definition.
How the topic appears in realistic exam-style scenarios.
Which detail in the question changes the correct answer.
How to eliminate plausible but wrong options.
How to connect the question back to the wider exam objective.
Watch out for
Common High Availability exam traps
- ▸Answering from memory before reading the full scenario.
- ▸Missing a constraint such as cost, availability, security, scope or command context.
- ▸Choosing a broad answer when the question asks for the most specific fix.
- ▸Ignoring why the wrong options are tempting.
Question index
All High Availability questions (58)
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Which THREE actions occur when a Junos router with GRES and NSR enabled performs a manual Routing Engine switchover while running OSPF and BGP? (Choose three)
Hard2You are troubleshooting a Virtual Chassis formed by four EX4300 switches. The primary Routing Engine (RE) unexpectedly rebooted. Upon recovery, you notice that a different member switch has taken over the role of primary. How can you prevent this specific member from becoming the primary RE in the future?
Hard3Which THREE conditions can cause a Virtual Chassis primary Routing Engine election or switchover to occur unexpectedly? (Choose three)
Hard4An engineer configures Nonstop Active Routing (NSR) on an MX series router. What is required for NSR to function properly on BGP peering sessions?
Medium5An engineer is preparing to perform an In-Service Software Upgrade (ISSU) on a pair of dual-RE MX240 routers. Which condition must be met to ensure the ISSU succeeds without dropping traffic?
Hard6An engineer configures a Virtual Chassis using EX4300 switches. To ensure member IDs are assigned consistently even if physical positions change, how should the administrator provision the member IDs?
Medium7You are troubleshooting a BGP session failure immediately following a manual Routing Engine switchover on an MX series router configured with GRES and NSR. BGP drops its peering session. What is the most likely reason for the failure?
Hard8When configuring a Link Aggregation Group (LAG) on a Juniper switch, what is the naming convention used for the aggregated interface in the Junos CLI?
Easy9Which command displays the status of Virtual Chassis member switches, their roles, and their serial numbers on an EX series switch?
Easy10You are performing a pre-check for an ISSU on an MX series router. You execute 'request system software in-service check' and the system reports an error indicating that graceful restart or NSR is not properly configured for active routing protocols. How do you resolve this?
Hard11You are troubleshooting a Virtual Chassis where member 0 has failed completely. The replacement switch arrives. Before inserting it into the running Virtual Chassis ring, what critical precaution must be taken regarding Junos OS software versions?
Hard12An administrator is configuring Graceful Restart on a pair of Juniper MX series routers running OSPF. What is the primary purpose of Graceful Restart in this scenario?
Easy13You are troubleshooting a split-brain condition in an EX4300 Virtual Chassis where both partitions have elected a primary Routing Engine. Which feature can be configured to detect this condition and shut down downstream ports on the non-designated partition to prevent duplicate packet forwarding?
Hard14An engineer wants to configure Nonstop Active Routing (NSR) alongside GRES on an MX204 router running OSPF. What is the primary operational benefit of enabling NSR compared to running GRES alone?
Medium15An engineer needs to configure a Link Aggregation Group (LAG) between two Juniper EX4300 switches to provide redundant uplinks to a core router. Which statements regarding the LACP configuration requirements on the EX4300 switch must be met?
Medium16An engineer configures VRRP between two routers. Client traffic destined for the outside network is being dropped intermittently. Investigation reveals that the VRRP master is responding to ARP requests with its physical MAC address instead of the virtual router MAC address. What is the cause of this behavior?
Medium17You are configuring VRRP between two EX4600 switches to provide a default gateway for a VLAN. To ensure that the switch with the higher physical interface capacity assumes the master role, what parameter should you adjust?
Medium18An administrator wants to verify that GRES is operating correctly on an MX series router with dual Routing Engines. Which operational command should be used?
Easy19Which THREE conditions must be met to successfully execute an In-Service Software Upgrade (ISSU) on a dual-RE Juniper routing platform? (Choose three)
Medium20Which CLI command is used to manually initiate a Routing Engine switchover on an MX series router configured with GRES?
Easy21Which CLI command displays detailed information about VRRP groups, including master router status, virtual IP addresses, and advertisement intervals on an EX series switch?
Easy22An administrator is configuring VRRP on an EX4300 switch and wants to ensure that when the primary router recovers from a failure, it immediately reclaims the master role from the backup router. Which VRRP configuration parameter controls this behavior?
Medium23An EX4300 Virtual Chassis has GRES enabled. During a primary Routing Engine failure, what happens to the backup Routing Engine?
Medium24Which THREE statements regarding Juniper Virtual Chassis architecture and master election are correct? (Choose three)
Hard25Which CLI command displays the operational status and roles of all members in a Juniper EX Series Virtual Chassis?
Easy26Which operational command allows you to view the real-time status of LACP packet exchanges and partner system IDs for an aggregated interface on a Junos switch?
Easy27An EX4300 Virtual Chassis experiences a split-brain condition due to a failure of all stacking cables between members 0/1 and members 2/3. How does Junos handle this scenario by default?
Medium28Which THREE statements accurately describe the behavior and configuration of VRRP tracking on Junos devices? (Choose three)
Hard29When configuring VRRP on a Juniper router, what IP address must be assigned as the virtual IP address for the group?
Easy30Which THREE parameters can be tuned under the VRRP hierarchy in Junos to customize failover timing and behavior? (Choose three)
Medium31When planning an In-Service Software Upgrade (ISSU) on a Juniper routing platform, what is the behavior of the Routing Engines during the execution of the upgrade command?
Hard32You are analyzing a core Juniper MX router after an ISSU upgrade procedure completed. You notice that BGP sessions dropped immediately after the final routing engine rebooted. What post-upgrade verification step should have been performed to prevent unexpected protocol drops during ISSU?
Hard33Which TWO operational commands are used to check the health and status of Routing Engines and GRES on an MX series router? (Choose two)
Easy34You are troubleshooting a VRRP deployment where two EX4600 switches are acting as redundant gateways for several VLANs. Clients on VLAN 10 report intermittent gateway unreachability. You notice that VRRP mastership frequently flips between Switch A and Switch B. What is the most effective way to stabilize VRRP mastership?
Hard35Which TWO items are required when configuring VRRP on a Juniper router interface? (Choose two)
Easy36You are troubleshooting a Link Aggregation Group (LAG) between an EX4300 switch and a third-party switch. Member links are flapping intermittently. Examination of system logs reveals LACP timeout errors. What is the most likely cause?
Hard37Which THREE criteria are evaluated by Junos when electing the primary Routing Engine in an EX Series Virtual Chassis? (Choose three)
Medium38You are configuring a Link Aggregation Group (LAG) with LACP on an EX3400 switch. You want to ensure that the interface bundle drops traffic if fewer than two active member links are operational. Which feature configuration achieves this?
Medium39You are troubleshooting an issue where an EX4300 Virtual Chassis fails to boot after adding a new switch member. The system console displays errors regarding incompatible Junos images and hardware mismatch on the Virtual Chassis ports. What is the correct procedure to recover and integrate the new member?
Hard40An administrator is setting up VRRP tracking on an EX4300 switch interface. If the uplink interface monitoring the core network fails, what should happen to the VRRP priority on the gateway interface?
Medium41Which TWO options represent valid benefits of configuring Link Aggregation Groups (LAG)? (Choose two)
Easy42Which CLI command verifies that OSPF Graceful Restart helper mode is enabled by default on a Juniper routing platform?
Easy43You are configuring Multi-Chassis Link Aggregation (MC-LAG) across two Juniper switches acting as separate control plane devices. Which protocol is used between the peer switches to synchronize state and ensure MAC address table consistency across the MC-LAG domain?
Hard44During an audit of a Juniper EX4300 Virtual Chassis, you notice that member 1 and member 2 are connected via mixed 1G and 10G uplink ports. How does Junos handle mixed-speed Virtual Chassis port configurations?
Hard45Which operational command displays the configured member IDs, priorities, and roles in an EX Series Virtual Chassis?
Easy46Which configuration command enables Graceful Routing Engine Switchover (GRES) globally on a Juniper routing platform?
Easy47An engineer configures a LAG between an EX4300 switch and a server. The server uses static LAG mode (no LACP). How must the Junos switch interface be configured to successfully form the bundle?
Medium48You notice frequent mastership transitions in a VRRP group configured between two EX4300 switches. The logs indicate that VRRP advertisements are intermittently missing. Which troubleshooting step addresses the underlying cause without changing the master priority?
Medium49Which TWO commands are used to verify link aggregation and LACP operational status on a Juniper switch? (Choose two)
Easy50You are configuring a Link Aggregation Group (LAG) on an EX series switch. Which statement is correct regarding LACP active mode?
Easy51Which CLI command displays the packet statistics, errors, and drop counters for a Link Aggregation Group (LAG) named ae0?
Easy52Which THREE potential issues can arise if LACP is misconfigured between a Juniper switch and a connected peer device? (Choose three)
Hard53Which THREE factors must be considered when configuring a Link Aggregation Group (LAG) with LACP on Junos switches? (Choose three)
Medium54You are verifying BGP Graceful Restart helper mode on a Juniper router. A peering router restarts its control plane. What output or verification command confirms that your router is acting as a Graceful Restart helper for the peer?
Hard55An administrator configures a Link Aggregation Group (LAG) using LACP between two EX series switches. The link fails to aggregate, and the log shows 'LACP status: Expired'. What does the 'Expired' state indicate?
Medium56Which TWO methods are used to connect switches in a Juniper EX Series Virtual Chassis? (Choose two)
Easy57An engineer wants to configure a Link Aggregation Group (LAG) to load-balance traffic based on Layer 3 and Layer 4 header fields (source/destination IP and source/destination port) rather than just Layer 2 MAC addresses. How is this achieved in Junos?
Medium58Which THREE statements are true regarding OSPF Graceful Restart helper mode on Juniper routers? (Choose three)
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Frequently asked questions
- What does the High Availability domain cover on the JNCIS-ENT exam?
- High Availability questions test whether you can apply the concept in context, not just recognise a definition.
- How many questions are in this domain?
- This page lists all 58 High Availability questions in the JNCIS-ENT question bank. The actual exam draws from this domain proportionally to its weighting in the official exam blueprint.
- What is the best way to practise this domain?
- Start with a short focused session (10 questions) to identify gaps, then work through explanations. Repeat with a longer session once the weak areas feel solid.
- Can I practise only High Availability questions?
- Yes — the session launcher on this page filters questions to this domain only. Choose any session length for inline explanations and scoring.