JN0-363 Sample Questions Answers

Junos devices learn about MAC addresses by examining the source MAC address of frames received on an interface and then storing these MAC addresses in the MAC address table (also known as the forwarding database) along with the interface on which the traffic was received.References:

• Understanding Learning and Forwarding, Juniper TechLibrary
• MAC Address Table Processing, Juniper TechLibrary

IPv6 link-local addresses are automatically generated for each interface and have a prefix of fe80::/10. The interface's MAC address is typically used as part of the process to create the Interface Identifier (IID) in the link-local address, following the EUI-64 format.

References

• Juniper Networks Technical Documentation on IPv6
• IPv6 Interface Addresses - Juniper Networks

The router identifier is used by BGP and OSPF to identify the routing device from which a packet originated. The router identifier usually is the IP address of the local routing device. If you do not configure a router identifier, the IP address of the first interface to come online is used. This is usually the loopback interface. Otherwise, the first hardware interface with an IP address is used

In OSPF, if a router ID is not manually configured, Junos OS will automatically select the router ID based on the highest IP address of any of the router’s loopback interfaces. If no loopback interface exists, the highest IP address of any active interface will be used. Therefore, answer C is correct.

References:

• Juniper Networks documentation on OSPF: OSPF Overview

The policy statement shown in the exhibit has a term that specifiesload-balance per-packet, which indicates that per-packet load balancing is being used. This means that the routing device will distribute packets out multiple paths on a per-packet basis, rather than on a per-flow (per-destination or per-source-destination pair) basis.

References:

• Juniper Networks documentation on Load Balancing: Load Balancing Overview

The IPv6 header includes a new field that is not found in the IPv4 header, called the flow label. The flow label in IPv6 is used to identify packets that require special handling by routers for quality of service (QoS) or other reasons, allowing these packets to be handled efficiently as they move through the network.

References

• Juniper Networks Technical Documentation on IPv6
• IPv6 Header Fields - Juniper Networks

By default, the router that originally sourced the route into BGP places its peer address into the attribute field. The next-hop value is then typically changed when the route is transmitted across external gGP (EBGP) links. Internal BGP (IBGP) peers do not alter the next-hop value between themselves.

B. By default, the next-hop value is changed when a route is passed from an EBGP peer to another EBGP peer.C. By default, the next-hop value is retained when a route is advertised across IBGP links.References:

• BGP Next Hop Attribute, Juniper TechLibrary
• Understanding BGP Next-Hop Selection, Juniper TechLibrary

When you want to advertise an interface in OSPF but not form an OSPF adjacency over that interface (for example, towards an ISP), you can configure the interface as passive. This will advertise the network on the interface in OSPF without sending OSPF hello packets or forming OSPF neighbor relationships on that interface.

References

• Juniper Networks Technical Documentation on OSPF
• OSPF Configuration Guide - Juniper Networks

An Integrated Routing and Bridging (IRB) interface is used to provide Layer 3 routing services to hosts within a bridge domain. The IRB acts as a default gateway for hosts in that domain, enabling communication with other networks.

References

• Juniper Networks Technical Documentation on IRB Interfaces

R2 can not forward IBGP learned routes to another IBGP neighbor correct

R3 will learn about Route X from R2 only. R1 is in a separate AS and Route X is advertised to R2 through eBGP. R2 will then advertise the route to R3 using iBGP. R3 cannot learn routes directly from another AS without having a direct eBGP session with that AS.References:

• BGP Route Propagation and Selection, Juniper Networks Documentation
• Understanding iBGP and eBGP Route Distribution, Juniper Networks Documentation

To enable MPLS on a physical interface in Junos, the family mpls statement must be added to the interface configuration. Additionally, the interface itself must be specifiedunder the protocols mpls section of the configuration.References:

• MPLS Configuration Guide, Juniper Networks Documentation
• Configuring MPLS, Juniper Networks Documentation

In BGP (Border Gateway Protocol), the Update message is used to advertise new routes to a peer or to withdraw previously advertised routes. If there's a change in the routing information or if a new route needs to be advertised, BGP uses an Update message. This message is crucial for maintaining the most current and accurate routing information among BGP peers.

The other message types serve different purposes:

Keepalive: This message type is used to maintain the connection between BGP peers and ensure that the link is still active. Keepalive messages are periodically sent between peers when there is no other BGP activity to maintain the session.

Notification: This message is used to indicate errors or other significant events to a BGP peer. If a BGP error condition is detected, a Notification message is sent and the BGP session is typically closed.

Refresh: This is not a standard BGP message type. However, in the context of BGP, Route Refresh is a capability (not a message type) that allows a BGP router to request a full or partial re-advertisement of routes from a peer. This helps in re-synchronizing routing tables without tearing down the BGP session.

The BGP Update message is used to advertise routable destinations and includes route advertisements, route withdrawals, and path attribute modifications. Update messages are used to re-advertise routes that have already been acknowledged.References:

• BGP Operations and Message Types Overview, Juniper Networks Documentation
• BGP Update Message, Juniper Networks Documentation

In MPLS (Multiprotocol Label Switching) networks, routers use label switching to forward packets. The first router at the edge of the MPLS network (R1) will perform a lookup in the mpls.0 table to determine the label to attach to the packet as it enters the MPLS network. This label informs the next routers in the MPLS network (like R2) on how to forward the packet. Internal MPLS routers, like R2, also perform lookups in their mpls.0 table to determine how to switch the packet toward its destination (label swapping). The inet.3 table is used for resolving next-hop information for labeled routes, but it's the mpls.0 table that is used for label switching decisions.

References:

• Juniper Networks documentation on MPLS: MPLS Applications User Guide for Routing Devices

When deploying Link Aggregation Groups (LAGs), it is necessary for all ports in the LAG to operate at the same speed to ensure consistent performance and avoid issues with load balancing. Multi-Chassis LAG (MC-LAG) allows for the use of member links that span multiple physical devices, offering redundancy and higher bandwidth by combining the links from two separate devices into a single logical LAG.

References

• Juniper Networks Technical Documentation on Link Aggregation Groups
• Juniper Networks Technical Documentation on MC-LAG

The exhibit shows the configuration of a virtual switch calledsw-1with two VLANs defined within it:vlan_1with VLAN ID 1 andvlan_2with VLAN ID 2. To add interfacexe-1/0/5to the virtual switch, the interface must be associated with one of these VLANs. Since the interface is already configured withvlan-id 2, it implies that it is intended to be part ofvlan_2within the virtual switchsw-1. Therefore, the correct answer is to add interfacexe-1/0/5to thevlan_2bridge domain under thesw-1routing instance.

References:

• Juniper documentation on virtual switches: Junos OS Routing Instances Overview

In a service provider MPLS network, P routers are interior routers that are used to transit MPLS-labeled packets between edge routers but do not attach or remove MPLS labels themselves. These routers are also referred to as transit routers. They are neither ingress nor egress routers (which are typically labeled as PE routers).

References:

• Juniper Networks documentation on MPLS: MPLS Fundamentals

metric—Metric value. Range: 1 through 63, or 1 through 16,777,215 (if you have configured wide metrics) Default: 10 (for all interfaces except lo0), 0 (for the lo0 interface)

https://www.cisco.com/c/en/us/support/docs/ip/open-shortest-path-first-ospf/13684-12.html#anc13

Neighbors Stuck in Exstart/Exchange State The problem occurs most frequently when you attempt to run OSPF between a Cisco router and another vendor router. The problem occurs when the maximum transmission unit (MTU) settings for neighboring router interfaces do not match. If the router with the higher MTU sends a packet larger that the MTU set on the neighboring router, the neighbor router ignores the packet. When this problem occurs, the output of the show ip ospf neighbor command displays output similar to what is shown in this figure.

A mismatched Maximum Transmission Unit (MTU) setting on OSPF interfaces can cause routers to get stuck in the ExStart state. OSPF requires that both sides of a link have the same MTU to form a full adjacency.References:

• OSPF Troubleshooting, Juniper Networks Documentation
• MTU and OSPF, Juniper Networks Documentation

In OSPF, an Area Border Router (ABR) that connects to a Not-So-Stubby Area (NSSA) will convert the Type 7 LSAs generated by an NSSA Autonomous System Boundary Router (ASBR) into Type 5 LSAs to advertise them into the OSPF backbone area (Area 0). Type 7 LSAs are specific to NSSAs and are used to advertise external routes within the NSSA.

References:

• Juniper Networks documentation on OSPF: OSPF Areas and LSA Types Explained

To create connections between routing instances on the same Junos device and route between them, you can use logical tunnel interfaces, which are virtual interfaces that can be used to route traffic between instances without the need for physical connectivity. Additionally, loopback interfaces, which represent the device itself, can be used to route traffic between routing instances as they are always up and can be reached within the device.

References

• Juniper Networks Technical Documentation on Routing Instances
• Juniper Networks Technical Documentation on Logical Tunnel Interfaces

When establishing an EBGP session, it's necessary to specify both the local AS number and the local address that the session will use. The local address is required for establishing the TCP connection for BGP. The local AS must be specified to identify the autonomous system of the router.References:

• Configuring BGP, Juniper TechLibrary
• BGP Peers and BGP Sessions, Juniper TechLibrary

The Segment Routing Global Block (SRGB) defines a range of MPLS labels reserved for segment routing. With an SRGB starting label of 10,000 and an index range of 500, the first usable label is indeed 10,001 because label 10,000 is typically reserved and not usedfor forwarding. The last usable label would be 10,499 because the range includes 500 labels starting from 10,001.

References:

• Juniper Networks documentation on Segment Routing: Segment Routing Overview

Given the RSVP Signaled Service Provider MPLS Core network shown in the exhibit, only a single Label Switched Path (LSP) is required to support all four networks because MPLS can use label stacking to multiplex multiple LSPs over a single physical path. Therefore, one LSP can be established through the MPLS core, and all networks can use this LSP with different label stacks.References:

• MPLS Fundamentals, Juniper Networks Documentation
• RSVP-TE Signaling, Juniper Networks Documentation