JN0-363 Service Provider Routing and Switching, Specialist (JNCIS-SP) Questions and Answers

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.

Referring to the configuration in the exhibit, R1 is set to export the 3rd_Policy to the neighbor at 192.168.1.5. Since 3rd_Policy permits the 10.200.3.0/24 prefix, only that prefix will be advertised to the neighbor.References:

• BGP Policies, Juniper Networks Documentation
• Policy Framework, Juniper Networks Documentation

only 10.200.3.0/24 will be advertised. The neighbor export overrides anything at the group level and protocol level. Policies aren't additive, you can't apply all three at the same time. What if one of them rejected a prefix while the other accepted the same one? You need one to override the other

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

The exhibit shows that the BGP session state is "Active," which generally indicates that the router is trying to establish a BGP session but has not received a response. One common cause for this issue is that there is no route to the BGP neighbor's address. Since the routers are using internal BGP (iBGP) and they are in the same AS, the AS number does not need to be unique, and anext-hop selfpolicy is not strictly required for iBGP. Therouter-idis usually automatically determined and does not need to be explicitly set.

References:

• Juniper Networks documentation on BGP: Troubleshooting BGP

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

Wide metrics in IS-IS allow for a larger metric value than what is available with narrow metrics, which supports a maximum of 63. Wide metrics also enable an interface to advertise different metrics for Level 1 and Level 2, allowing for more flexible routing policies and greater scalability in large networks.References:

• IS-IS Wide Metrics, Juniper Networks Documentation
• Configuring IS-IS Wide Metrics, Juniper Networks Documentation

In IS-IS, Level 1 routes are usually contained within the same area and Level 2 routes are used to interconnect different areas. By default, routes from Level 1 are redistributed into Level 2, and vice versa, to ensure reachability between areas.

References

• Juniper Networks Technical Documentation on IS-IS

By default, IS-IS protocol leaks routing information from a Level 1 area to a Level 2 area. However, to leak routing information from a Level 2 area to a Level 1 area, an export policy must be explicitly configured.

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

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

According to the exhibit, the primary LSP is configured with a strict path via R2 to R4. Since the configuration shows valid next-hops and there is no indication of any issues, the primary LSP will be signaled and its state will be up. The secondary LSP with any-path is also configured and will be signaled as a backup; therefore, its state will be up as well, ready to take over if the primary fails.References:

• MPLS LSP Configuration, Juniper Networks Documentation
• Configuring Primary and Secondary LSPs, Juniper Networks Documentation

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

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

In Junos OS, traffic engineering extensions for OSPF, which are required for an LSP to use the OSPF link state database for path computations, are not enabled by default. They must be explicitly enabled in the OSPF configuration. Therefore, answer C is correct. Answer B is incorrect and contradicts C. The 'no-cspf' command would disable CSPF (Constrained Shortest Path First), which is used for path computations in MPLS traffic engineering, so it should not be used if you want the LSP to utilize OSPF's link state database for path computations. Therefore, answer A is incorrect. The 'policing' parameter is not relevant to enabling traffic engineering extensions in OSPF, so answer D is incorrect.

References:

• Juniper Networks documentation on OSPF and Traffic Engineering: Configuring OSPF Traffic Engineering

https://www.juniper.net/documentation/us/en/software/junos/ospf/topics/topic-map/configuring-ospf-support-for-traffic-engineering.html

https://zartmann.dk/sr-intro/

In segment routing, SIDs (Segment Identifiers) are used to identify different types of segments that can be traversed. A node SID represents an instruction to route a packet to a particular node, and an adjacency SID represents an instruction to route a packet over a specific link or adjacency between two nodes.

References

• Juniper Networks Technical Documentation on Segment Routing

Segment routing labels can be distributed by link-state routing protocols such as IS-IS and OSPF, which have been extended to support segment routing capabilities.References:

• Segment Routing Overview, Juniper Networks Documentation
• Understanding Segment Routing with OSPF, Juniper Networks Documentation
• Understanding Segment Routing with IS-IS, Juniper Networks Documentation

https://www.juniper.net/documentation/us/en/software/junos/static-routing/topics/ref/statement/qualified-next-hop-edit-routing-options.html

https://www.juniper.net/documentation/us/en/software/junos/static-routing/topics/topic-map/static-route-prefer-qualified-next-hop.html: Qualified next hops allow you to associate one or more properties with a particular next-hop address. You can set an overall preference for a particular static route and then specify a different preference for the qualified next hop. For example, suppose two next-hop addresses (10.10.10.10 and 10.10.10.7) are associated with the static route 192.168.47.5/32. A general preference is assigned to the entire static route, and then a different preference is assigned to only the qualified next-hop address 10.10.10.7. For example:

The qualified-next-hop statement with a static route is used to specify multiple next hops for a static route with different preferences (priorities). This allows for more granular control over the path selection process in the event that the primary next hop becomes unreachable.References:

• Static Routes Overview, Juniper Networks Documentation
• Example: Configuring Qualified Next Hop, Juniper Networks Documentation

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

To test connectivity to a server from within a specific routing instance, you use thepingcommand along with therouting-instanceoption to specify the routing instance from which you are pinging. This is necessary because the routing table associated withvr3is separate from the main routing table, and you must explicitly tell the device to use thevr3routing table to reach the server.

References:

• Juniper Networks documentation on Routing Instances: Routing Instances Overview

Considering the bandwidth reservations shown, the only path from R4 to R6 that has sufficient available bandwidth for a new LSP with 400 Mbps reservation is via R1, R2, and R5. This is because the R4-R5 direct link and the R4-R1-R2-R3-R6 path do not have enough unreserved bandwidth to accommodate an additional 400 Mbps LSP.

References:

• Juniper Networks documentation on RSVP: RSVP-TE Overview

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

https://www.juniper.net/documentation/us/en/software/junos/mpls/topics/topic-map/lsp-routers.html

In an MPLS network, the types of routers include ingress routers (where the MPLS labels are first applied), egress routers (where MPLS labels are removed), and transit routers (which switch MPLS-labeled packets through the MPLS network). Peering routers andaggregation routers are not specific types of MPLS routers; they are general network terms.

References:

• Juniper Networks documentation on MPLS: MPLS Fundamentals

For IS-IS to form adjacencies, the 'family iso' statement must be configured on the interface. This is required because IS-IS operates over the connectionless network service (CLNS) and not over IP. Without the 'family iso' configuration, IS-IS cannot form adjacencies over the interface.

References:

• Juniper Networks documentation on IS-IS: IS-IS User Guide for Routing Devices