Juniper Updated JN0-664 Exam Questions and Answers by angelo

In PIM-SM (Protocol Independent Multicast - Sparse Mode), the Designated Router (DR) plays a crucial role in multicast forwarding. The DR is responsible for various tasks depending on whether it is connected to the source or the receiver. Let's analyze each statement regarding the PIM DR in a PIM-SM domain.

1. **Statement A: The source DR sends PIM register messages from the source network to the RP.**

- Correct. In PIM-SM, the DR on the source's local network is responsible for encapsulating multicast packets in PIM Register messages and sending them to the Rendezvous Point (RP). This process ensures that the RP is aware of active sources.

2. **Statement B: If the DR priorities match, the router with the lowest IP address is selected as the DR.**

- Incorrect. The correct rule is that if the DR priorities match, the router with the **highest** IP address is selected as the DR. The election process first compares priorities; if priorities are equal, the IP addresses are compared to select the DR.

3. **Statement C: The receiver DR sends PIM join and PIM prune messages from the receiver network toward the RP.**

- Correct. In PIM-SM, the DR on the receiver's local network sends PIM Join messages toward the RP to join the multicast distribution tree. Similarly, it sends PIM Prune messages to leave the tree when there are no interested receivers.

4. **Statement D: By default, PIM DR election is performed on point-to-point links.**

- Incorrect. By default, PIM DR election is performed on multi-access networks (e.g., Ethernet). On point-to-point links, there is no need for a DR election as there are only two routers involved.

**Conclusion**:

The correct statements regarding the PIM DR in a PIM-SM domain are:

**A. The source DR sends PIM register messages from the source network to the RP.**

**C. The receiver DR sends PIM join and PIM prune messages from the receiver network toward the RP.**

**References**:

- Juniper Networks Documentation on PIM-SM: [PIM-SM Overview](https://www.juniper.net/documentation/en_US/junos/topics/concept/pim-sparse-mode-overview.html)

- RFC 7761, Protocol Independent Multicast - Sparse Mode (PIM-SM): [RFC 7761](https://tools.ietf.org/html/rfc7761) which details the PIM-SM protocol, including DR roles and election procedures.

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.

In the context of Layer 3 VPNs (L3VPN) using MPLS, the routing information for different customers (VPNs) is typically stored in separate routing tables (VRFs). When you want to verify that PE2 is receiving the VPN routes for Customer C from PE1, you need to check the appropriate VRF routing table on PE2.

1. **Option A: show route table customer-c.inet.0**

- This command displays the routing table specific to Customer C's VRF.

- Since we want to verify that PE2 has received the VPN routes for Customer C, this is the most appropriate command to use.

- It allows us to see all routes learned for Customer C's VPN.

2. **Option B: show route table bgp.l3vpn.0**

- This command displays the BGP routing table for all L3VPN routes.

- While this includes routes for Customer C, it also includes routes for all other VPNs, making it harder to isolate the specific information for Customer C.

- This command is more useful for an overall view of BGP L3VPN routes rather than for a specific customer's VRF.

3. **Option C: show route summary**

- This command provides a summary of the routes in all routing tables.

- It doesn't give detailed information about the specific routes for Customer C's VRF.

- It's useful for a high-level overview but not for verifying specific customer routes.

4. **Option D: show route table inet.0**

- This command shows the global routing table, not the VRF-specific tables.

- The global routing table doesn't contain the VPN-specific routes that are stored in the VRF tables.

- Therefore, it won't help in verifying the routes for Customer C.

**Conclusion**:

To verify that PE2 is receiving VPN routes for Customer C from PE1, the most appropriate command is to check the specific VRF routing table for Customer C. Hence, the correct answer is:

**A. show route table customer-c.inet.0**

**References**:

- Junos OS documentation on MPLS VPNs: [Junos MPLS VPNs Guide](https://www.juniper.net/documentation/en_US/junos/topics/topic-map/mpls-vpns.html)

- Command Reference for Routing Tables: [Junos OS Routing Tables Command Reference](https://www.juniper.net/documentation/en_US/junos/topics/reference/command-summary/show-route-table.html)

EVPN is a solution that provides Ethernet multipoint services over MPLS networks. EVPN uses BGP to distribute endpoint provisioning information and set up pseudowires between PE devices. EVPN uses different route types to convey different information in the control plane. The following are the main EVPN route types:

Type 1 - Ethernet Auto-Discovery Route: This route type is used for network-wide messaging and discovery of other PE devices that are part of the same EVPN instance. It also carries information about the redundancy mode and load balancing algorithm of the PE devices.

Type 2 - MAC/IP Advertisement Route: This route type is used for MAC and IP address learning and advertisement between PE devices. It also carries information about the Ethernet segment identifier (ESI) and the label for forwarding traffic to the MAC or IP address.

Type 3 - Inclusive Multicast Ethernet Tag Route: This route type is used for broadcast, unknown unicast, and multicast (BUM) traffic forwarding. It also carries information about the multicast group and the label for forwarding BUM traffic.

Type 4 - Ethernet Segment Route: This route type is used for multihoming scenarios, where a CE device is connected to more than one PE device. It also carries information about the ESI and the designated forwarder (DF) election process.