Upon a link failure in an RSVP-signaled LSP, the router upstream of the failure (R2) sends a PathTear message upstream to the ingress router (R1), and the router downstream of the failure (R3) sends a ResvTear message downstream to the egress router (R4). These messages signal the failure and initiate tear down of the LSP state in the respective directions.References:

• RSVP-TE Overview, Juniper Networks Documentation
• Understanding RSVP Signal Failures, Juniper Networks Documentation

To prevent a router from participating in the OSPF designated router (DR) and backup designated router (BDR) election process, you set the OSPF priority to 0 on the interfaces of that router. This tells OSPF that the router on those interfaces is not to be considered for election as either DR or BDR, effectively making them DRother routers. The exhibit indicates that this is the desired configuration, and therefore the correct command to issue on the Juniper device would be to set the priority to 0 on the relevant interfaces.

Thenext-hop-self-policypolicy is used to alter the next-hop attribute of BGP routes. When you apply it as an export policy to an external BGP (eBGP) group, it changes the next-hop attribute of the routes being advertised to eBGP neighbors so that the next-hop IP address is the IP address of the router itself. This ensures that the eBGP neighbors use the local router as the next hop to reach these routes.

References

• Juniper Networks Technical Documentation on BGP Policies

https://www.networkfuntimes.com/junos-aggregate-routes-vs-generate-routes-how-to-summarise-on-juniper-routers/

Generated routes are a type of route that can be created to summarize and generate more specific routes within the routing table. Unlike aggregate routes, which summarize existing routes and inherit a next-hop, generated routes do not necessarily have to match an existing route and will have a next-hop of reject by default unless specified otherwise.

References

• Juniper Networks Technical Documentation on Routing Policies and Route Generation

By default, BGP will propagate routes learned from EBGP peers to other IBGP peers. However, due to the BGP split-horizon rule, routes learned from one IBGP peer are notre-advertised to another IBGP peer. This behavior is designed to prevent routing information loops within the same AS.

References:

• Juniper Networks documentation on BGP: BGP Route Propagation and Selection

The exhibit shows theshow vrrp summaryoutput from two routers, with both routers listing the state of their VRRP group asmaster. VRRP allows for multiple routers to share a virtual IP address and a virtual MAC address, but usually, only one router is the master at any given time while others are in backup state. However, in some configurations, VRRP can operate in an active/active mode where multiple routers handle traffic simultaneously for load sharing. Since both routers show the state asmasterand there is no evidence of misconfiguration in the virtual IP addresses or priority, it indicates that VRRP is likely functioning in an active/active setup.

References:

• Juniper documentation on VRRP: Junos OS VRRP Overview

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

Local preference is a BGP attribute that dictates which path is preferred when multiple paths to the same destination are available. A higher local preference is preferred over a lower one. Since ISP A (AS 65501) is advertising a local preference of 100 and ISP B (AS 65502) is advertising a local preference of 200 to AS 65512, traffic from devices in AS 65512 will prefer the path via ISP B for all networks that ISP B advertises. However, since ISP A advertises the 172.20.21.0/24 network and ISP B does not, traffic for 172.20.21.0/24 will go through ISP A. For the 172.20.0.0/24 network, which both ISPs advertise, devices in AS 65512 will prefer the path via ISP B due to the higher local preference.

References:

• Juniper Networks documentation on BGP attributes: BGP Attributes and Policy

The AS path is a BGP attribute that lists the autonomous systems (AS) that routing information has passed through to get to a destination. It is used to detect and prevent routing loops by checking if the router's own AS number is in the path.

References:

• Juniper Networks documentation on BGP: BGP Attributes and Policy

the Database Description (DD) packets serve two main purposes:

1. determinining which router is in charge of the database synchronization

2. tansferring the LSA headers between the two systems

The Database Description (DBD) OSPF packet is used during the adjacency formation process to describe the contents of the topological database between routers. The routers exchange DBD packets to determine the master and slave relationship, which dictates the router in charge of the database synchronization.References:

• OSPF Design Guide, Juniper Networks Documentation
• OSPF Database Description Packets, Juniper Networks Documentation

static route with a next-hop of next-table pointing to the appropriate routing table which contains more accurate information rib-groups to mirror routing information from one route-table to another. However, in many cases, in order to make this work, interface-routes also need to be mirrored. RIB Group policy can be used to constrain the routing information instance-import and instance-export statements configured within the individual routing-instances to leak routes from one table to another. Again, policy can be used here to constrain the routing information. This method is more straightforward than the rib-group method A final approach is to use physical interfaces or logical-tunnels to stitch routing-instances and use a routing protocol or static routes across this connection between the two routing-instances.

To share routes between two routing instances on a Junos device, you can configure an instance import policy in one or both instances to import routes from the other instance. Alternatively, a RIB (Routing Information Base) group can be used to share routes between instances.References:

• Routing Instances Overview, Juniper Networks Documentation
• RIB Groups Configuration Guide, Juniper Networks Documentation

IS-IS is a link-state routing protocol that uses a Shortest Path First (SPF) algorithm to create a topology map of the network. It floods link-state advertisements (LSAs) to all nodes within the network area to ensure each node has a consistent view of the network topology.

References

• Juniper Networks Technical Documentation on IS-IS
• Understanding IS-IS - Juniper Networks

In VRRP (Virtual Router Redundancy Protocol), the router with the highest priority is elected as the master (primary) router. In the exhibit, routers R1 and R4 are both configured with a VRRP priority of 90. Since R2 and R3 have default priorities (which are lower than 90), they will not be elected over R1 or R4. Between R1 and R4, if all else is equal, the router with the numerically higher IP address becomes the master. However, if not enough information is provided to determine which of R1 or R4 has the higher IP address, the answer would be the one explicitly mentioned with the highest priority.

References:

• Juniper Networks documentation on VRRP: VRRP Overview

https://www.juniper.net/documentation/us/en/software/junos/high-availability/topics/task/nsr-configuring.html

Nonstop routing (NSR) requires both Graceful Routing Engine Switchover (GRES) and commit synchronization to be configured to maintain routing protocol and forwarding state during a Routing Engine switchover. NSR allows the secondary Routing Engine to take over the control plane without the protocols needing to restart, and GRES ensuresthat the forwarding plane continues operating with the current forwarding table. Commit synchronization ensures that configuration changes are synchronized between the primary and backup Routing Engines.

References:

• Juniper Networks documentation on High Availability: Configuring Nonstop Active Routing

To verify the status of the tunnel from R1, you would issue a ping from the source address that is assigned to R1's end of the tunnel. In the exhibit, we can see that the tunnel interface (gre-0/0/0.0) has the IP address 198.51.100.1 on R1. Therefore, to test the tunnel's status, you should ping the IP address at the other end of the tunnel (which is likely the address on User B's interface or another interface on R2) from R1's tunnel source address.

References:

• Juniper Networks documentation on GRE: GRE Interface Configuration

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

In the exhibit, the interface is configured with thenative-vlan-id 20parameter. This means that any untagged frames arriving on this interface will be associated with VLAN 20. The native VLAN serves as the default VLAN for untagged frames on a trunk port.

References:

• Juniper Networks documentation on VLANs: Configuring VLANs

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

The exhibit shows that the Label Switched Path (LSP) is down. One common reason for this could be that the IGP is not providing traffic engineering information to the MPLS process. Since the exhibit shows the OSPF configuration, enabling traffic engineering extensions for OSPF would allow OSPF to distribute the labels and traffic engineering information necessary for LSP establishment.

References

• Juniper Networks Technical Documentation on MPLS and OSPF

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

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)

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