Juniper JN0-664 JNCIP-SP Exam Practice Test Instant Access

Question 1

Which two statements describe PIM-SM? (Choose two)

ARouters with receivers send join messages to their upstream neighbors.

BRouters without receivers must periodically prune themselves from the SPT.

CTraffic is initially flooded to all routers and an S,G is maintained for each group

DTraffic is only forwarded to routers that request to join the distribution tree.

Answer : A, D

PIM sparse mode (PIM-SM) is a multicast routing protocol that uses a pull model to deliver multicast traffic. In PIM-SM, routers with receivers send join messages to their upstream neighbors toward a rendezvous point (RP) or a source-specific tree (SPT). The RP or SPT acts as the root of a shared distribution tree for a multicast group. Traffic is only forwarded to routers that request to join the distribution tree by sending join messages. PIM-SM does not flood traffic to all routers or prune routers without receivers, as PIM dense mode does.

Question 2

Refer to the exhibit.

Click the Exhibit button.

Referring to the exhibit, you must provide VRF Internet access over a single connection for VPN-A Site 1, which connects to PE-1.

Which two statements are correct in this scenario? (Choose two.)

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

BYou do not need to use the RIB group to move interface routes from the inet. o table to the VPN-A. inet. 0 table.

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

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

Answer : A, B

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.**

**Reference**:

- 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)

Question 3

Exhibit

You must ensure that the VPN backbone is preferred over the back door intra-area link as long as the VPN is available. Referring to the exhibit, which action will accomplish this task?

AConfigure an import routing policy on the CE routers that rejects OSPF routes learned on the backup intra-area link.

BEnable OSPF traffic-engineering.

CConfigure the OSPF metric on the backup intra-area link that is higher than the L3VPN link.

DCreate an OSPF sham link between the PE routers.

Answer : D

A sham link is a logical link between two PE routers that belong to the same OSPF area but are connected through an L3VPN. A sham link makes the PE routers appear as if they are directly connected, and prevents OSPF from preferring an intra-area back door link over the VPN backbone.To create a sham link, you need to configure the local and remote addresses of the PE routers under the [edit protocols ospf area area-id] hierarchy level1.

https://www.juniper.net/documentation/us/en/software/junos/ospf/topics/topic-map/configuring-ospfv2-sham-links.html

Question 4

Refer to the exhibit.

Click the Exhibit button.

PE-1 and PE-2 are configured with LDP-signaled pseudowires to provide connectivity between CE-1 and CE-2. You notice no connectivity exists between CE-1 and CE-2.

Referring to the exhibit, which two statements describe potential causes for this fault? (Choose two.)

AThe VC IDs are mismatched.

BThere is no LSP configured from PE-1 to PE-2.

CInterface ge-0/0/0 on PE-1 is down.

DThere is no LSP configured from PE-2 to PE-1.

Answer : A, D

Question 5

Which two statements about IS-IS are correct? (Choose two.)

APSNPs are used to acknowledge a received LSP.

BCSNPs are used to acknowledge a received LSP.

CCSNPs are used to request a missing LSP.

DPSNPs are used to request a missing LSP.

Answer : A, D

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.**

**Reference**:

- 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.

Question 6

Which two statements are correct about the customer interface in an LDP-signaled pseudowire? (Choose two)

AWhen the encapsulation is vlan-ccc or extended-vlan-ccc, the configured VLAN tag is not included in the control plane LDP advertisement

BWhen the encapsulation is ethernet-ccc, only frames without a VLAN tag are accepted in the data plane

CWhen the encapsulation is vLan-ccc or extended-vlan-ccc, the configured VLAN tag is included in the control plane LDP advertisement

DWhen the encapsulation is ethemet-ccc, tagged and untagged frames are both accepted in the data plane.

Answer : C, D

The customer interface in an LDP-signaled pseudowire is the interface on the PE router that connects to the CE device. An LDP-signaled pseudowire is a type of Layer 2 circuit that uses LDP to establish a point-to-point connection between two PE routers over an MPLS network. The customer interface can have different encapsulation types depending on the type of traffic that is carried over the pseudowire. The encapsulation types are ethernet-ccc, vlan-ccc, extended-vlan-ccc, atm-ccc, frame-relay-ccc, ppp-ccc, cisco-hdlc-ccc, and tcc-ccc. Depending on the encapsulation type, the customer interface can accept or reject tagged or untagged frames in the data plane, and include or exclude VLAN tags in the control plane LDP advertisement. The following table summarizes the behavior of different encapsulation types:

Question 7

Exhibit

CE-1 must advertise ten subnets to PE-1 using BGP Once CE-1 starts advertising the subnets to PE-1, the BGP peering state changes to Active.

Referring to the CLI output shown in the exhibit, which statement is correct?

ACE-1 is advertising its entire routing table.

BCE-1 is configured with an incorrect peer AS

CThe prefix limit has been reached on PE-1

DCE-1 is unreachable

Answer : C

Analyzing the Exhibit and Understanding the Issue

The exhibit shows BGP configurations on CE-1 and PE-1, which are connected via EBGP.

CE-1 (Customer Edge)

Uses AS 64511 and establishes an EBGP session with PE-1 (AS 65550).

Configured to export 10 static routes (192.168.1.0/24 - 192.168.10.0/24) using the static-to-bgp policy.

PE-1 (Provider Edge)

Uses AS 65550 and is peering with CE-1 (AS 64511).

Configured with a prefix-limit of 5 on received routes from CE-1.

Teardown enabled, meaning if more than 5 prefixes are received, the BGP session is shut down.

Identifying the Problem

CE-1 is correctly configured with peer AS 65550, so Option B ('CE-1 is configured with an incorrect peer AS') is incorrect .

CE-1 is advertising exactly 10 static routes (as per policy).

PE-1 has a prefix-limit maximum 5 with teardown enabled.

This means that when CE-1 advertises more than 5 prefixes, PE-1 shuts down the BGP session.

BGP moves to the 'Active' state, indicating that the session has been disrupted and PE-1 is trying to re-establish the connection.

CE-1 is reachable since the session was initially established before the limit was exceeded, so Option D ('CE-1 is unreachable') is incorrect .

CE-1 is not advertising its entire routing table, only the static prefixes listed in the policy, so Option A ('CE-1 is advertising its entire routing table') is incorrect .

Correct Answer

C. The prefix limit has been reached on PE-1

Verification from Juniper Documentation

Juniper BGP Prefix Limit Documentation confirms that exceeding the prefix limit with teardown causes the BGP session to go into 'Active' state.

Juniper Troubleshooting Guide for BGP Peering Issues states that when a BGP session reaches the prefix limit and has teardown enabled, the session is terminated.

Juniper Service Provider Routing and Switching, Professional Exam JN0-664 JNCIP-SP Exam Practice Test