JN0-664 Juniper Service Provider Professional (JNCIP-SP) Free Practice Exam Questions (2025 Updated)

This is an EVPN Type-2 route, also called a MAC/IP advertisement route, that is used to advertise host IP and MAC address information to other VTEPs in an EVPN network. The route type field in the EVPN NLRI has a value of 2, indicating a Type-2 route. The device advertising this route into EVPN is 192.168.101.5, which is the IP address of the VTEP that learned the host information from the local CE device. This IP address is carried in the MPLS label field of the route as part of the VXLAN encapsulation.

Option A (Correct):

In IS-IS, the Designated Intermediate System (DIS) is elected based on the highest configured priority (as defined in Junos OS).

If priorities are equal, the router with the highest MAC address becomes the DIS.

A priority value of 10 will always override a lower priority (e.g., 1).

In the provided exhibit, the configuration involves using a RIB (Routing Information Base) group to facilitate internet access for VPN-A Site 1 through PE-1. The goal is to provide VRF Internet access over a single connection.

1. **Understanding RIB Groups**:

- RIB groups allow for the import and export of routes between different routing tables.

- In this scenario, we have two RIBs: `inet.0` (the main routing table) and `VPN-A.inet.0` (the VRF-specific routing table).

2. **Statement Analysis**:

- **A. You must use the RIB group to move a default route, which is learned through BGP, from the inet.0 table to the VPN-A.inet.0 table.**

- Correct. To provide Internet access to VPN-A, the default route (0.0.0.0/0) learned via BGP in the `inet.0` table must be made available in the `VPN-A.inet.0` table. This is done using the RIB group to import the default route.

- **B. You do not need to use the RIB group to move interface routes from the inet.0 table to the VPN-A.inet.0 table.**

- Correct. Interface routes (connected routes) are typically directly added to both the global and the VRF routing tables without needing a RIB group. These routes are known to the VRF because the interfaces are part of the VRF configuration.

- **C. You do not need to use the RIB group default route, which is learned through BGP, from the inet.0 table to the VPN-A.inet.0 table.**

- Incorrect. As discussed, the default route needs to be imported into the VRF's routing table using a RIB group to enable Internet access for the VRF.

- **D. You must use the RIB group to move interface routes from the inet.0 table to the VPN-A.inet.0 table.**

- Incorrect. Interface routes are directly associated with the VRF interfaces and are automatically known to the VRF routing table. There is no need to use a RIB group for these routes.

**Conclusion**:

The correct answers are:

**A. You must use the RIB group to move a default route, which is learned through BGP, from the inet.0 table to the VPN-A.inet.0 table.**

**B. You do not need to use the RIB group to move interface routes from the inet.0 table to the VPN-A.inet.0 table.**

**References**:

- Juniper Networks Documentation on RIB Groups: [RIB Groups Overview](https://www.juniper.net/documentation/en_US/junos/topics/concept/rib-groups-overview.html)

- Junos OS VPNs Configuration Guide: [Junos VPNs Configuration](https://www.juniper.net/documentation/en_US/junos/topics/concept/vpns-overview.html)

https://www.juniper.net/documentation/us/en/software/junos/cos/topics/concept/packet-flow-cos-process-cos-config-guide.html

BGP add-path is a feature that allows the advertisement of multiple paths through the same peering session for the same prefix without the new paths implicitly replacing any previous paths. This behavior promotes path diversity and reduces multi-exit discriminator (MED) oscillations. BGP add-path is implemented by adding a path identifier to each path in the NLRI. The path identifier can be considered as something similar to a route distinguisher in VPNs, except that a path ID can apply to any address family. Path IDs are unique to a peering session and are generated for each network3. In this question, we have a route reflector (RR) that receives two routes for the same prefix (192.168.0.0/16) from an EBGP neighbor. By default, the RR will only advertise its best path to its clients (R1 and R2). However, we want R1 and R2 to receive both routes from the RR. To achieve this, we need to configure BGP add-path on the RR and enable it to send multiple paths for the same prefix to its clients.

https://www.juniper.net/documentation/us/en/software/nce/feature-guide-virtual-private-lan-service/topics/task/vpls-ldp-signaling-solutions.html

https://www.juniper.net/documentation/us/en/software/junos/vpn-l2/topics/concept/vpns-configuring-vpls-routing-instances.html#id-11510150__id-11568648

Intermediate System to Intermediate System (IS-IS) is a link-state routing protocol used to move information efficiently within a computer network. It uses a series of Protocol Data Units (PDUs) to manage the network's topology and ensure consistency across all routers in the network. Specifically, Link State PDUs (LSPs), Complete Sequence Number PDUs (CSNPs), and Partial Sequence Number PDUs (PSNPs) play crucial roles in this process.

1. **PSNPs (Partial Sequence Number PDUs)**:

- **Acknowledge a received LSP**: PSNPs are used to acknowledge the receipt of LSPs. When a router receives an LSP, it sends a PSNP back to the sender to confirm that the LSP has been received.

- **Request a missing LSP**: PSNPs are also used to request missing LSPs. If a router identifies a missing LSP based on sequence numbers, it can send a PSNP to request the specific LSP from its neighbors.

2. **CSNPs (Complete Sequence Number PDUs)**:

- **Summarize LSPs**: CSNPs are used to summarize all the LSPs known to a router. They are typically sent at regular intervals to provide a complete list of LSPs in a database. They are not used to acknowledge or request specific LSPs but provide an overview of all LSPs for database synchronization.

Based on this understanding, let's evaluate the statements:

- **A. PSNPs are used to acknowledge a received LSP.**

- Correct. PSNPs serve the purpose of acknowledging LSPs received from other routers.

- **B. CSNPs are used to acknowledge a received LSP.**

- Incorrect. CSNPs are not used for acknowledging LSPs; they are used to provide a summary of all LSPs.

- **C. CSNPs are used to request a missing LSP.**

- Incorrect. CSNPs are not used to request missing LSPs; this is the role of PSNPs.

- **D. PSNPs are used to request a missing LSP.**

- Correct. PSNPs are used to request specific missing LSPs when a router detects that it is missing information.

**Conclusion**:

The correct statements about IS-IS are:

**A. PSNPs are used to acknowledge a received LSP.**

**D. PSNPs are used to request a missing LSP.**

**References**:

- Juniper Networks Documentation on IS-IS: [IS-IS Overview](https://www.juniper.net/documentation/en_US/junos/topics/concept/is-is-routing-overview.html)

- RFC 1195, Use of OSI IS-IS for Routing in TCP/IP and Dual Environments: [RFC 1195](https://tools.ietf.org/html/rfc1195) which details the operation and use of IS-IS, including the roles of PSNPs and CSNPs.

https://www.juniper.net/documentation/us/en/software/junos/traffic-mgmt-qfx/topics/concept/cos-qfx-series-default-scheduling-classification-understanding.html

The auto-export parameter is a routing option that allows a routing instance to share routes with other routing instances or the master routing table. The auto-export parameter automatically exports routes from one routing instance to another based on the route target communities attached to the routes. In this scenario, the 10.101.1.0/24 route will be shared if the auto-export parameter is configured under [edit routing-options] hierarchy level.

The provided configuration is for a routing instance named VPN-A on a Juniper PE (Provider Edge) router. Let’s break it down:

Instance Type: VRF

The instance-type vrf; statement indicates that this is a Layer 3 VPN (L3VPN) using MPLS VPNs (RFC 4364 – BGP/MPLS IP VPNs).

This confirms that Option D (A Layer 3 VPN is configured) is correct ✅.

VRF Target and Interface Association

The vrf-target target:64512:1234; defines the route target (RT) for importing and exporting VPN routes.

The interface ge-0/0/1.0; binds this interface to the VRF.

BGP Configuration for CE (Customer Edge) Peering

The group CE section configures external BGP (EBGP) (type external;).

The neighbor 10.0.0.1 is in AS 64512 (peer-as 64512;).

The as-override; statement is used.

Evaluating the Answer Choices

✅ Option B: "This VPN connects customer sites that use the same AS number."

The as-override; command allows multiple customer sites that use the same AS number (64512) to communicate over the service provider’s MPLS network.

Normally, BGP prevents routes with the same AS in the AS_PATH from being accepted. The as-override feature replaces the customer's AS number with the provider’s AS, ensuring proper route advertisement.

✅ This statement is correct.

❌ Option A: "This VPN connects customer sites that use different AS numbers."

If the customer sites had different AS numbers, there would be no need for as-override.

The as-override feature is specifically used when all customer sites share the same AS number, ensuring that BGP routes are accepted.

❌ This statement is incorrect.

❌ Option C: "A Layer 2 VPN is configured."

A Layer 2 VPN (L2VPN) configuration would typically use instance-type l2vpn; or EVPN/VPLS-related parameters (e.g., protocols l2vpn or protocols vpls).

Since this configuration uses instance-type vrf; and BGP with a VRF target, it is clearly a Layer 3 VPN (L3VPN).

❌ This statement is incorrect.

✅ Option D: "A Layer 3 VPN is configured."

The instance-type vrf; confirms this is an MPLS Layer 3 VPN (L3VPN).

VRFs, BGP, and route targets (vrf-target) are specific to Layer 3 VPNs.

✅ This statement is correct.

Final Answer:

✅ B. This VPN connects customer sites that use the same AS number.

✅ D. A Layer 3 VPN is configured.

Verification from Juniper Documentation:

Juniper BGP/MPLS Layer 3 VPNs Guide confirms that instance-type vrf is used for L3VPNs.

Juniper BGP Configuration Guide states that as-override is applied when customer sites use the same AS number.

RFC 4364 (BGP/MPLS IP VPNs) explains how route targets and VRFs are used in L3VPN deployments.

In the exhibit, the PE-to-CE protocol used is OSPF, and there is an OSPF neighborship between CE-1 and CE-2 within the same Area 0. Let's analyze the default OSPF routing behavior in this setup to determine the correct statement.

1. **OSPF Neighborship**:

- CE-1 and CE-2 have an OSPF neighborship directly within Area 0.

- OSPF prefers intra-area routes over inter-area and external routes.

2. **Default Routing Behavior**:

- Since CE-1 and CE-2 are directly connected through an OSPF link within the same area, OSPF will prefer this direct intra-area path over any other paths learned via the PE routers and the L3VPN.

- This is because intra-area routes have a lower metric compared to inter-area or external routes.

3. **Metric Considerations**:

- By default, OSPF will route traffic between Site-1 and Site-2 through the direct link between CE-1 and CE-2, unless the link's metric is artificially increased to make it less preferable.

- There is no need to adjust metrics for the CE-1 to PE-1 link to prefer the CE-1 to CE-2 path, as OSPF already prefers direct intra-area paths.

**Conclusion**:

Given the default behavior of OSPF and the topology shown in the exhibit, the correct statement is:

**B. Hosts at Site-1 will reach hosts at Site-2 through the CE-1 and CE-2 link by default.**

**References**:

- OSPF Design Guide: [Juniper Networks OSPF Design Guide](https://www.juniper.net/documentation/en_US/junos/topics/concept/ospf-design-overview.html)

- Juniper Networks Technical Documentation on OSPF: [Junos OS OSPF Configuration Guide](https://www.juniper.net/documentation/en_US/junos/topics/concept/ospf-routing-overview.html)

BGP route reflectors are BGP routers that are allowed to ignore the IBGP loop avoidance rule and advertise IBGP learned routes to other IBGP peers under specific conditions. BGP route reflectors can reduce the number of IBGP sessions and updates in a network by eliminating the need for a full mesh of IBGP peers. BGP route reflectors can have three types of peerings:

EBGP neighbor: A BGP router that belongs to a different autonomous system (AS) than the route reflector.

IBGP client neighbor: An IBGP router that receives reflected routes from the route reflector. A client does not need to peer with other clients or non-clients.

IBGP non-client neighbor: An IBGP router that does not receive reflected routes from the route reflector. A non-client needs to peer with other non-clients and the route reflector.

In the exhibit, we can see that RR1 and RR2 are route reflectors in the same AS with reachability redundancy. They have two types of peerings: EBGP neighbors (R1 and R4) and IBGP client neighbors (Client1, Client2, and Client3). RR1 and RR2 are also peered with each other as IBGP non-client neighbors.

In an L2VPN scenario, the provider network connects two customer edge (CE) devices across a Layer 2 virtual private network. Let's analyze how OSPF operates in this setup.

1. **OSPF Neighborship in L2VPN**:

- An L2VPN provides a Layer 2 connection between two sites, making it transparent to Layer 3 protocols like OSPF. This means the CEs can form OSPF adjacencies directly with each other as if they were on the same local network.

2. **OSPF Configuration on CEs and PEs**:

- **Statement A: OSPF neighborship is formed between the CEs and PEs**:

- Incorrect. In an L2VPN, the provider's network is transparent to the OSPF running on the CEs. OSPF neighborship forms directly between the CEs, not between the CEs and PEs.

- **Statement B: The CE and PE OSPF areas can be different**:

- Correct. Since OSPF adjacencies form directly between the CEs and not between CEs and PEs, the OSPF areas on the CEs and PEs can be different. The provider network acts as a transparent bridge, and OSPF doesn't see the PEs.

- **Statement C: The CE and PE OSPF areas must match**:

- Incorrect. As noted above, because the OSPF neighborship forms directly between the CEs, the OSPF areas on the CEs and PEs do not need to match.

- **Statement D: OSPF neighborship is formed between the two CEs**:

- Correct. The L2VPN makes the connection between the two CEs appear as a direct Layer 2 link, allowing them to form an OSPF adjacency directly.

**Conclusion**:

Given the above analysis, the correct statements are:

**B. The CE and PE OSPF areas can be different.**

**D. OSPF neighborship is formed between the two CEs.**

**References**:

- Juniper Networks Documentation on L2VPNs: [Configuring Layer 2 VPNs](https://www.juniper.net/documentation/en_US/junos/topics/task/configuration/layer-2-vpns-configuring.html)

- OSPF Configuration Guide: [Junos OS OSPF Configuration](https://www.juniper.net/documentation/en_US/junos/topics/concept/ospf-routing-overview.html)

IS-IS is an interior gateway protocol that uses link-state routing to exchange routing information among routers within a single autonomous system. IS-IS uses two types of addresses to identify routers and areas: system ID and area address. The system ID is a unique identifier for each router in an IS-IS domain. The system ID is 6 octets long and can be derived from the MAC address or manually configured. The area address is a variable-length identifier for each area in an IS-IS domain. The area address can be 1 to 13 octets long and is composed of high-order octets of the address. An IS-IS instance may be assigned multiple area addresses, which are considered synonymous. Multiple synonymous area addresses are useful when merging or splitting areas in the domain1. In this question, we have a network based on IS-IS with four routers (R1_1, R1_2, R2_1, and R2_2) belonging to area 0001. The area address for area 0001 is 49.0001. The NSEL byte for area 0001 is the last octet of the address, which is 01. The NSEL byte stands for Network Service Access Point Selector (NSAP Selector) and indicates the type of service requested from the network layer2. Therefore, the correct statement in this scenario is that the NSEL byte for area 0001 is 01.

BGP Layer 2 VPNs use BGP to distribute endpoint provisioning information and set up pseudowires between PE devices. BGP uses the Layer 2 VPN (L2VPN) Routing Information Base (RIB) to store endpoint provisioning information, which is updated each time any Layer 2 virtual forwarding instance (VFI) is configured. The prefix and path information is stored in the L2VPN database, which allows BGP to make decisions about the best path.

In BGP Layer 2 VPNs, each site has a unique site ID that identifies it within a VFI. The site ID can be manually configured or automatically assigned by the PE device. By default, the site ID is automatically assigned based on the order that you add the interfaces to the site configuration. The first interface added to a site configuration has a site ID of 1, the second interface added has a site ID of 2, and so on.

Option D is correct because by default on PE-2, the remote site IDs are automatically assigned based on the order that you add the interfaces to the site configuration. Option A is not correct because by default on PE-2, the site’s local ID is automatically assigned a value of 0 and does not need to be configured to match the total number of attached sites. Option B is not correct because you do not need to create a unique Layer 2 VPN routing instance for each site on the PE-2 device. You can create one routing instance for all sites within a VFI. Option C is not correct because you do not need to use separate physical interfaces to connect PE-2 to each site. You can use subinterfaces or service instances on a single physical interface.

https://www.juniper.net/documentation/us/en/software/junos/routing-policy/bgp/topics/example/bgp-advertise-peer-as.html

Layer 2 VPNs don’t support fragmentation in the provider network. It is critical that the provider network supports the largest frame that the CE devices can generate after the MPLS and virtual routing and forwarding (VRF) labels are added by the PE devices. This example leaves the CE devices at the default 1500-byte maximum transmission unit (MTU) while configuring the provider core to support a 4000 byte MTU. This configuration avoids discards by ensuring the CE devices cannot exceed the MTU in the provider’s network.