Pass the Juniper JNCIP-SP JN0-664 Questions and answers with CertsForce

AToM (Any Transport over MPLS) is a framework that supports various Layer 2 transport types over an MPLS network core. One of the transport types supported by AToM is LDP Layer 2 circuit, which is a point-to-point Layer 2 connection that uses LDP for signaling and MPLS for forwarding. LDP Layer 2 circuit can support Layer 2 connectivity without using BGP and can be scalable and efficient by using a single MPLS LSP for multiple VPN connections. The customer can maintain all routing for their private network by using their own CE switches.

https://www.juniper.net/documentation/us/en/software/junos/cli-reference/topics/ref/command/show-route-advertising-protocol.html

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

This configuration applies to IGMP (Internet Group Management Protocol) and is designed to control multicast group memberships on the interface ge-0/0/0.0.

Breaking Down the Configuration

1️⃣ Policy-Statement: block-igmp

policy-statement block-igmp {

term 1 {

from {

route-filter 224.7.7.7/32 exact;

source-address-filter 192.168.100.10/32 exact;

}

then reject;

}

}

This policy blocks IGMP joins for group 224.7.7.7 only if the source IP is 192.168.100.10.

If both conditions match, the request is rejected.

2️⃣ IGMP Configuration on Interface ge-0/0/0.0

[edit protocols igmp]

user@router# show

interface ge-0/0/0.0 {

group-policy block-igmp;

group-limit 25;

}

group-policy block-igmp applies the policy statement block-igmp, meaning IGMP join requests are evaluated based on this policy.

group-limit 25 means the interface allows up to 25 multicast groups.

Evaluating the Answer Choices

✅ A. Joins for group 224.7.7.7 are rejected if the source address is 192.168.100.10.

Correct, because:

The policy specifically matches group 224.7.7.7 and source IP 192.168.100.10.

If both conditions are met, the join is rejected.

❌ B. Joins for any group are accepted if the group count value is less than 25.

Incorrect, because:

The group-limit (25) applies to the total number of IGMP groups but does not override explicit policy rules.

Even if there are fewer than 25 groups, a join request can still be rejected by the policy statement.

❌ C. Joins for group 224.7.7.7 are always rejected, regardless of the group count.

Incorrect, because:

The policy only blocks joins from the specific source 192.168.100.10.

Joins from other sources to 224.7.7.7 are allowed.

❌ D. Joins for group 224.7.7.7 are accepted if the group count is less than 25.

Incorrect, because:

Joins for 224.7.7.7 from source 192.168.100.10 will always be rejected, even if the group count is below 25.

The group-limit does not override the rejection policy.

"Joins for group 224.7.7.7 are rejected if the source address is 192.168.100.10."

???? Official Juniper Documentation Reference:

???? Junos IGMP Policy Configuration Guide

"A group-policy statement allows filtering IGMP joins based on multicast group address and source IP."

TLVs are tuples of (Type, Length, Value) that can be advertised in IS-IS packets. TLVs can carry different kinds of information in the Link State Packets (LSPs). IS-IS supports both narrow and wide metrics for link costs. Narrow metrics use a single octet to encode the link cost, while wide metrics use three octets. Narrow metrics have a maximum value of 63, while wide metrics have a maximum value of 16777215. If there are both narrow and wide metric devices in the topology, IS-IS will advertise two TLVs for each link: one with the narrow metric and one with the wide metric. This allows backward compatibility with older devices that only support narrow metrics12.

In IS-IS (Intermediate System to Intermediate System) routing, each router is identified by a unique ISO (International Organization for Standardization) address, also known as a Network Entity Title (NET). The NET consists of three parts:

1. **Area Identifier**: Indicates the area to which the router belongs.

2. **System Identifier**: Uniquely identifies the router within the area.

3. **NSAP Selector (NSEL)**: Typically set to 00 for a router, indicating the Network Service Access Point.

The format of the ISO address is `49.XXXX.YYYY.YYYY.ZZZZ.ZZZZ.00`, where:

- `49` is the AFI (Authority and Format Identifier) indicating a private address.

- `XXXX` is the Area Identifier.

- `YYYY.YYYY.YYYY` is the System Identifier.

- `ZZZZ.ZZZZ` is the NSAP Selector.

Given the address `49.0001.00a0.c96b.c490.00`:

- **Area Identifier**: `49.0001`

- **System Identifier**: `00a0.c96b.c490`

- **NSAP Selector**: `00`

**Explanation**:

- **A. 00a0.c96b.c490 is the system identifier**:

- Correct. The System Identifier in an ISO address is a 48-bit (6-byte) field used to uniquely identify the router. In this address, `00a0.c96b.c490` is the correct 6-byte System Identifier.

- **B. 0001.00a0.c96b.c490 is the system identifier**:

- Incorrect. This includes the Area Identifier as part of the System Identifier, which is not correct.

- **C. c96b.c490 is the system identifier**:

- Incorrect. This is only part of the System Identifier. The full System Identifier must be 6 bytes long.

- **D. c490 is the system identifier**:

- Incorrect. This is an incomplete and incorrect part of the System Identifier.

**Conclusion**:

The correct part of the address that represents the System Identifier is:

**A. 00a0.c96b.c490 is the system identifier.**

**References**:

- Juniper Networks Documentation on IS-IS: [IS-IS Configuration](https://www.juniper.net/documentation/en_US/junos/topics/task/configuration/isis-configuring.html)

- ISO/IEC 10589, the IS-IS routing protocol standard.

Prefer the route with the lower origin code. Routes learned from an IGP have a lower origin code than those learned from an exterior gateway protocol (EGP), and both have lower origin codes than incomplete routes (routes whose origin is unknown). https://www.juniper.net/documentation/us/en/software/junos/vpn-l2/bgp/topics/concept/routing-protocols-address-representation.html

Type 1: When Type value is 1, the Administrator field is 4-bytes and Assigned Number field is 2-bytes. The Administrator field should be set to the IP address (public IP addresses should be used). The Assigned Number field contains a number from a numbering space that is administered by the enterprise to which the IP address has been assigned by the appropriate authority.