JN0-664 Service Provider Professional (JNCIP-SP) Questions and Answers

https://www.juniper.net/documentation/us/en/software/junos/sampling-forwarding-monitoring/bgp/topics/concept/bgp-multipath-unequal-understanding.html

The route distinguisher (RD) is a BGP attribute that is used to create unique VPN IPv4 prefixes for each VPN in an MPLS network. The RD is a 64-bit value that consists of two parts: an administrator field and an assigned number field. The administrator field can be an AS number or an IP address, and the assigned number field can be any arbitrary value chosen by the administrator. The RD is prepended to the IPv4 prefix to create a VPN IPv4 prefix that can be advertised across the MPLS network without causing any overlap or conflict with other VPNs. In this question, we have two PE routers (PE-1 and PE-2) that are connected to two CE devices (CE-1 and CE-2) respectively. PE-1 and PE-2 are configured with VRFs named Customer-A and Customer-B respectively. 

In OSPF, routers form adjacencies by exchanging Hello packets. These packets contain several parameters that must match between OSPF neighbors to establish a successful adjacency. Key among these parameters are the Hello Interval and the Dead Interval.

Let's analyze the exhibit and the question to determine the correct course of action to ensure that R4 peers with both R1 and R2.

1. **OSPF Hello and Dead Intervals**:

- **Hello Interval**: The time in seconds between Hello packets sent out by a router. Default is usually 10 seconds for broadcast and point-to-point networks.

- **Dead Interval**: The time in seconds that a router will wait to receive a Hello packet from a neighbor before declaring the neighbor down. Default is usually four times the Hello Interval (40 seconds).

2. **Analysis of the Exhibit**:

- **R1's Interface**: Shows a Dead Interval of 40 seconds.

- **R2's Interface**: Shows a Dead Interval of 40 seconds.

- **R4's Interface**: Shows a Dead Interval of 20 seconds.

From the exhibit, we can see that R4 has a Dead Interval of 20 seconds, while R1 and R2 have Dead Intervals of 40 seconds. This discrepancy prevents R4 from establishing an OSPF peering with R1.

3. **Option Analysis**:

- **A. Adjust the Priority on R1 to be lower than the Priority on R4**:

- Incorrect. The OSPF Priority is used for DR/BDR election on multi-access networks and does not impact peering issues.

- **B. Change the MTU size on R1 and R2 to be 22 bytes higher than R4's MTU size**:

- Incorrect. While MTU mismatches can prevent OSPF adjacencies, the exhibit does not indicate an MTU mismatch issue.

- **C. Adjust the Dead Interval on R4 to match the Dead Interval on R1 and R2**:

- Correct. Matching the Dead Interval on R4 to 40 seconds will ensure that all routers have consistent Hello and Dead Intervals, allowing OSPF adjacencies to form.

- **D. Adjust the Hello Interval on R1 and R2 to match the Hello Interval on R4**:

- While this would be a valid approach if the Hello Intervals were mismatched, the exhibit shows that the Hello Intervals are consistent (10 seconds) across all routers. Therefore, this adjustment is not necessary.

**Conclusion**:

To correct the OSPF peering issue, the Dead Interval on R4 should be adjusted to match the Dead Intervals on R1 and R2. The correct answer is:

**C. Adjust the Dead Interval on R4 to match the Dead Interval on R1 and R2.**

**References**:

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

- OSPF Configuration Guide: [Configuring OSPF](https://www.juniper.net/documentation/en_US/junos/topics/task/configuration/ospf-configuring.html)

In the context of Ethernet VPN (EVPN) and the behavior described in the exhibit, it's essential to understand the different EVPN route types and their specific functionalities. Here, CE-2 is receiving unicast traffic on both of its multihomed links to PE-2 and PE-3, but broadcast traffic is received only on one of these links.

**Explanation of EVPN Route Types**:

1. **Type 1 (Ethernet Auto-Discovery Routes)**:

- These routes are used for auto-discovery of Ethernet segments and for advertising VLAN membership.

- They do not directly influence the behavior described in the question.

2. **Type 2 (MAC/IP Advertisement Routes)**:

- These routes are used to advertise MAC addresses and IP-to-MAC bindings within the EVPN.

- They handle unicast traffic forwarding and are crucial for populating the MAC address tables on the PE devices.

- While important, they do not explain the selective broadcast behavior.

3. **Type 3 (Inclusive Multicast Ethernet Tag Routes)**:

- These routes are used to build multicast distribution trees for delivering broadcast, unknown unicast, and multicast (BUM) traffic.

- They ensure that BUM traffic is sent only once per Ethernet segment, preventing duplicate frames from being sent to multihomed CEs.

- This aligns with the behavior described where CE-2 receives broadcast traffic on only one link to prevent duplication.

4. **Type 4 (Ethernet Segment Routes)**:

- These routes are used to advertise the presence of an Ethernet segment and are crucial for Designated Forwarder (DF) election processes in multihoming scenarios.

- While relevant to multihoming, they are not directly responsible for the selective broadcast behavior.

**Conclusion**:

The behavior described, where CE-2 receives broadcast traffic on only one of its multihomed links, is controlled by Type 3 routes. These routes are specifically designed to handle inclusive multicast and broadcast traffic efficiently in EVPN environments, ensuring that such traffic is not duplicated across multiple links to the same CE.

**References**:

- Juniper Networks EVPN Documentation: [EVPN Overview](https://www.juniper.net/documentation/en_US/junos/topics/concept/evpn-overview.html)

- RFC 7432, BGP MPLS-Based Ethernet VPN: [RFC 7432](https://tools.ietf.org/html/rfc7432) provides detailed descriptions of EVPN route types and their functions.

- Junos OS EVPN Configuration Guide: [Junos OS EVPN Configuration Guide](https://www.juniper.net/documentation/en_US/junos/topics/topic-map/evpn.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.

In the exhibit, the output of the `show route protocol bgp` command is shown for the prefix `172.16.20.4/30`. Let's analyze the provided BGP routing table to determine which statements are correct.

1. **AS Path Analysis**:

- The AS path for the route `172.16.20.4/30` is shown as `2 I`.

- This indicates that the route was learned from AS 2 and it is an internal (iBGP) route within the same AS.

2. **Multiple Paths**:

- The route has two next-hop IP addresses: `10.0.18.2` via interface `ge-1/0/4.0` and `10.0.19.2` via interface `ge-1/0/5.0`.

- This indicates that BGP multipath is configured, which allows multiple equal-cost paths to be used for load balancing.

- BGP multipath must be explicitly configured to use multiple paths for the same prefix.

3. **Multihop vs. Multipath**:

- **Multihop Configuration**: This is typically used for establishing BGP sessions with peers that are not directly connected. It is not related to load balancing.

- **Multipath Configuration**: This is used to enable load balancing across multiple paths for the same prefix, which is the case here.

**Conclusion**:

Given the above analysis:

- **C. This route is learned from the same AS number**: Correct. The AS path `2 I` indicates the route was learned from the same AS number (AS 2).

- **D. The multipath configuration is used for load balancing**: Correct. The presence of multiple next-hops indicates that BGP multipath is configured for load balancing.

Thus, the correct answers are:

**C. This route is learned from the same AS number.**

**D. The multipath configuration is used for load balancing.**

**References**:

- Junos OS BGP Multipath Documentation: [Junos OS BGP Multipath](https://www.juniper.net/documentation/en_US/junos/topics/topic-map/bgp-multipath.html)

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

The attached bit is a flag in an IS-IS LSP that indicates whether a router is connected to another area or level (L2) of the network. By default, L2 routers set this bit when they advertise their LSPs to L1 routers, and L1 routers use this bit to select a default route to reach other areas or levels through L2 routers. However, this may result in suboptimal routing if there are multiple L2 routers with different paths to other areas or levels. To ensure that L1 routers have only the most specific routes available from L2 routers, you can configure the ignore-attached-bit parameter on all L1 routers. This makes L1 routers ignore the attached bit and install all interarea routes learned from L2 routers in their routing tables.

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.

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)

BGP is an exterior gateway protocol that uses path vector routing to exchange routing information among autonomous systems. BGP uses various attributes to select the best path to each destination and to propagate routing policies. Some of the common BGP attributes are AS path, next hop, local preference, MED, origin, weight, and community. BGP attributes can be classified into four categories: well-known mandatory, well-known discretionary, optional transitive, and optional nontransitive. Well-known mandatory attributes are attributes that must be present in every BGP update message and must be recognized by every BGP speaker. Well-known discretionary attributes are attributes that may or may not be present in a BGP update message but must be recognized by every BGP speaker. Optional transitive attributes are attributes that may or may not be present in a BGP update message and may or may not be recognized by a BGP speaker. If an optional transitive attribute is not recognized by a BGP speaker, it is passed along to the next BGP speaker. Optional nontransitive attributes are attributes that may or may not be present in a BGP update message and may or may not be recognized by a BGP speaker. If an optional nontransitive attribute is not recognized by a BGP speaker, it is not passed along to the next BGP speaker. In this question, we have four routers (R1, R2, R3, and R4) that are connected in a full mesh topology and running IBGP. R3 receives the 192.168.0.0/16 route from its EBGP neighbor and advertises it to R1 and R4 with different BGP attribute values. We are asked which statements are correct about the BGP routes on R3 that are learned from the ISP-A neighbor. Based on the information given, we can infer that the correct statements are:

By default, the next-hop value for these routes is not changed by ISP-A before being sent to R3. This is because the default behavior of EBGP is to preserve the next-hop attribute of the routes received from another EBGP neighbor. The next-hop attribute indicates the IP address of the router that should be used as the next hop to reach the destination network.

The BGP local-preference value that is used by ISP-A is not advertised to R3. This is because the local-preference attribute is a well-known discretionary attribute that is used to influence the outbound traffic from an autonomous system. The local-preference attribute is only propagated within an autonomous system and is not advertised to external neighbors.

References: : https://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/13753-25.html : https://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/13762-40.html : https://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/13759-37.html

Route reflection is a BGP feature that allows a router to reflect routes learned from one IBGP peer to another IBGP peer, without requiring a full-mesh IBGP topology. Route reflectors do not change any existing BGP attributes by default when advertising routes, unless explicitly configured to do so. A BGP peer does not require any configuration changes to become a route reflector client, only the route reflector needs to be configured with the client parameter under [edit protocols bgp group group-name neighbor neighbor-address] hierarchy level.

https://www.juniper.net/documentation/us/en/software/junos/bgp/topics/ref/statement/multihop-edit-protocols-bgp.html

The class-of-service (CoS) configuration in the exhibit shows how traffic is scheduled on the ge-0/0/0 interface. Let's analyze each statement to determine its correctness:

A. Incoming traffic will not be classified because no classifier exists in the configuration.

This statement is correct. The configuration shown does not include any classifier, so no explicit classification is defined. As a result, incoming traffic will not be classified according to any custom criteria.

B. The best-effort queue can transmit more than 40% of the total bandwidth on the ge-0/0/0 interface, if no other queue is using that bandwidth.

This statement is correct. The transmit-rate percent 40 means that 40% of the bandwidth is guaranteed for the best-effort queue, but it can use more bandwidth if other queues (like the priority scheduler) are not utilizing their allocated bandwidth.

C. Incoming traffic will be classified using the default classifier.

This statement is incorrect. Without an explicit classifier in the configuration, there is no mention of a default classifier being used. Therefore, the incoming traffic won't be classified based on the configuration shown.

D. The best-effort queue can never transmit more than 40% of the total bandwidth on the ge-0/0/0 interface, even if that bandwidth is available.

This statement is incorrect. The transmit-rate percent 40 sets a guaranteed minimum bandwidth but does not set a maximum limit. The best-effort queue can utilize more bandwidth if other queues are not using their allocated portions.

BGP FlowSpec is a feature that extends the Border Gateway Protocol (BGP) to enable routers to exchange traffic flow specifications, allowing for more precise control of network traffic. The BGP FlowSpec feature enables routers to advertise and receive information about specific flows in the network, such as those originating from a particular source or destined for a particular destination. Routers can then use this information to construct traffic filters that allow or deny packets of a certain type, rate limit flows, or perform other actions1. BGP FlowSpec can also help in filtering traffic and taking action against distributed denial of service (DDoS) attacks by dropping the DDoS traffic or diverting it to an analyzer2. BGP FlowSpec rules are internally converted to equivalent Cisco Common Classification Policy Language (C3PL) representing corresponding match and action parameters2. Therefore, BGP FlowSpec uses dynamically created routing policies to protect a network from denial-of-service attacks.

References: 1: https://www.networkingsignal.com/what-is-bgp-flowspec/  2: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_bgp/configuration/xe-16/irg-xe-16-book/bgp-flowspec-route-reflector-support.html

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.

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.

The vrf-target export parameter is used to specify one or more BGP extended community attributes that are attached to VPN routes when they are exported from a VRF routing instance to remote PE routers. This parameter allows you to control which VPN routes are accepted by remote PE routers based on their import policies. You can specify more than one vrf-target export value for a VRF routing instance to support advanced route filtering or route leaking scenarios.

To transport IPv6 traffic over an IPv4-based MPLS network using BGP, you need to configure two address families: family inet6 labeled-unicast and family inet6 unicast. The former is used to exchange IPv6 routes with MPLS labels between PE routers, and the latter is used to exchange IPv6 routes without labels between PE and CE routers. The mpis ipv6-tunneling command enables the PE routers to encapsulate the IPv6 packets with an MPLS label stack and an IPv4 header before sending them over the MPLS network.

In the provided exhibit, the output of the `show pim join extensive 232.1.1.1` command is shown. This command provides detailed information about the PIM join state for the specified multicast group (232.1.1.1) on the router R1. To determine the correct statements regarding the multicast traffic, let's analyze the output and the terms involved:

1. **ASM vs. SSM**:

- **ASM (Any-Source Multicast)**: In ASM, receivers are interested in receiving multicast traffic from any source sending to a particular multicast group.

- **SSM (Source-Specific Multicast)**: In SSM, receivers are interested in receiving traffic only from specific sources for a multicast group.

- **Group Address Range**:

- ASM uses the range 224.0.0.0 to 239.255.255.255.

- SSM uses the range 232.0.0.0 to 232.255.255.255.

Since the group address 232.1.1.1 falls within the SSM range (232.0.0.0/8), there might be confusion. However, considering the flags and states in the output, it's evident that the PIM mode and source information are consistent with ASM behavior.

2. **Multicast Trees**:

- **RPT (Rendezvous Point Tree)**: Multicast traffic initially uses the RPT, where the Rendezvous Point (RP) acts as an intermediate point.

- **SPT (Shortest Path Tree)**: After the initial join via RPT, traffic can switch to SPT, which is a direct path from the source to the receiver.

3. **Output Analysis**:

- **Flags**:

- The flags `sparse, rp-tree, wildcard` indicate that the group 232.1.1.1 is currently using RPT. This is typical for ASM, where traffic initially goes through the RP.

- The flags `sparse, spt` indicate that for the source 172.16.1.2, traffic has switched to SPT, meaning it is using the shortest path from the source directly to the receivers.

**Conclusion**:

Based on the analysis:

- **A. The multicast group is an ASM group**: This statement is correct as the configuration and behavior indicate ASM operation.

- **B. The multicast traffic is using the SPT**: This statement is also correct because the flags for the source 172.16.1.2 indicate that the traffic is using the SPT.

Thus, the correct answers are:

**A. The multicast group is an ASM group.**

**B. The multicast traffic is using the SPT.**

**References**:

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

- Junos OS Multicast Routing Configuration Guide: [Multicast Routing Configuration Guide](https://www.juniper.net/documentation/en_US/junos/topics/topic-map/multicast-routing.html)

class-of-service (CoS) is a feature that allows you to prioritize and manage network traffic based on various criteria, such as application type, user group, or packet loss priority. CoS uses different components to classify, mark, queue, schedule, shape, and drop traffic according to the configured policies.

One of the components of CoS is drop profiles, which define how packets are dropped when a queue is congested. Drop profiles use random early detection (RED) algorithm to drop packets randomly before the queue is full, which helps to avoid global synchronization and improve network performance. Drop profiles can be discrete or interpolated. A discrete drop profile maps a specific fill level of a queue to a specific drop probability. An interpolated drop profile maps a range of fill levels of a queue to a range of drop probabilities and interpolates the values in between.

In the exhibit, we can see that the class-of-service configuration shows an interpolated drop profile with two fill levels (50 and 75) and two drop probabilities (20 and 60). Based on this configuration, we can infer the following statements:

The drop probability jumps immediately from 20% to 60% when the queue level reaches 75% full. This is not correct because the drop profile is interpolated, not discrete. This means that the drop probability gradually increases from 20% to 60% as the queue level increases from 50% full to 75% full. The drop probability for any fill level between 50% and 75% can be calculated by using linear interpolation formula.

The drop probability gradually increases from 20% to 60% as the queue level increases from 50% full to 75% full. This is correct because the drop profile is interpolated and uses linear interpolation formula to calculate the drop probability for any fill level between 50% and 75%. For example, if the fill level is 60%, the drop probability is 28%, which is calculated by using the formula: (60 - 50) / (75 - 50) * (60 - 20) + 20 = 28.

To use this drop profile, you reference it in a scheduler. This is correct because a scheduler is a component of CoS that determines how packets are dequeued from different queues and transmitted on an interface. A scheduler can reference a drop profile by using the random-detect statement under the [edit class-of-service schedulers] hierarchy level. For example: scheduler test { transmit-rate percent 10; buffer-size percent 10; random-detect test-profile; }

To use this drop profile, you apply it directly to an interface. This is not correct because a drop profile cannot be applied directly to an interface. A drop profile can only be referenced by a scheduler, which can be applied to an interface by using the scheduler-map statement under the [edit class-of-service interfaces] hierarchy level. For example: interfaces ge-0/0/0 { unit 0 { scheduler-map test-map; } }

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.