JN0-664 Exam Dumps : Service Provider Professional (JNCIP-SP)

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.

The exhibit shows the configuration of a VRF (Virtual Routing and Forwarding) instance on a Juniper PE router. Let's break down the key components:

VRF Configuration (VPN-A)

The instance type is VRF, meaning this is an L3VPN (Layer 3 VPN).

The routing instance contains a static route (10.1.0.0/16 next-hop 10.1.0.1).

The interface ge-0/0/2.0 is assigned to the VRF.

Route Distinguisher (RD): 172.17.20.1:1

VRF-Export Policy: vpn-a-export

VRF-Target: target:65512:1 (This defines which routes will be imported into the VRF).

VRF Export Policy (vpn-a-export)

The vpn-a-export policy adds two BGP communities (route targets) to exported VPN routes:

community add vpn-a-target;

community add vpn-m-target;

accept;

The vpn-a-target community corresponds to target:65512:1.

The vpn-m-target community corresponds to target:65512:2.

Policy-Options (Community Definitions)

community vpn-a-target members target:65512:1;

community vpn-m-target members target:65512:2;

This confirms that routes exported from this VRF will have BOTH target:65512:1 and target:65512:2.

Evaluating the Answer Choices

✅ Option A: "VPN routes are exported with the target:65512:1 and target:65512:2 route targets."

The vpn-a-export policy explicitly adds both vpn-a-target (65512:1) and vpn-m-target (65512:2) to exported routes.

This is correct. ✅

❌ Option B: "You cannot use the vrf-target and vrf-export statements in the same VRF."

This is incorrect.

Juniper allows the use of both vrf-target and vrf-export in the same VRF:

vrf-target is used for importing routes.

vrf-export defines export policies (which can add additional route targets).

This is incorrect. ❌

❌ Option C: "VPN routes with the target:65512:1 and target:65512:2 route targets are imported."

The vrf-target target:65512:1; statement only controls importing routes.

The import policy does not include target:65512:2, so routes tagged with target:65512:2 alone would not be imported into this VRF.

This is incorrect. ❌

❌ Option D: "VPN routes are exported with only the target:65512:1 route target."

The export policy (vpn-a-export) clearly adds both 65512:1 and 65512:2.

This is incorrect. ❌

Final Answer:

✅ A. VPN routes are exported with the target:65512:1 and target:65512:2 route targets.

Verification from Juniper Documentation

Juniper MPLS L3VPN Configuration Guide confirms that vrf-target is used for importing, while vrf-export can be used for exporting multiple route targets.

Juniper Routing Policy Documentation states that export policies can add multiple BGP communities (route targets).

RFC 4364 (BGP/MPLS IP VPNs) defines the use of route targets for VPN route control.

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.