JN0-664 Exam Dumps - Juniper JNCIP-SP Questions and Answers

In IS-IS, a designated intermediate system (DIS) is a router that is elected on a multi-access network segment (such as Ethernet) to perform some functions on behalf of other routers on the same segment. A DIS is responsible for sending network link-state advertisements (LSPs), which describe all the routers attached to the network. These LSPs are flooded throughout a single area. A DIS also generates pseudonode LSPs, which represent the multi-access network as a single node in the link-state database. A DIS election is based on the priority value configured on each router’s interface connected to the multi-access network. The priority value ranges from 0 to 127, with higher values indicating higher priority. The router with the highest priority becomes the DIS for the area (Level 1, Level 2, or both). If routers have the same priority, then the router with the highest MAC address is elected as the DIS. By default, routers have a priority value of 64. On a multi-access network, each router only forms an adjacency to the DIS, not to every other router on the segment. This reduces the amount of hello packets and LSP

Class of Service (CoS) in networking is used to manage traffic by classifying, scheduling, and sometimes modifying packets to ensure network performance and Quality of Service (QoS). Different CoS components are used to achieve these goals. Let's analyze each option to determine which CoS component allows you to alter class-of-service values on the outbound interface of an edge router.

1. **Output Policer**:

- Policing is used to control the rate of traffic sent to or from a network interface. It can drop or remark traffic that exceeds a certain rate.

- Policing is not typically used to alter CoS values but to enforce traffic limits.

2. **Scheduler**:

- A scheduler is responsible for managing the order in which packets are transmitted out of an interface based on their CoS markings. It can allocate bandwidth and prioritize traffic.

- The scheduler manages how packets are queued and sent but does not alter the CoS values of packets.

3. **Rewrite Rules**:

- Rewrite rules are used to modify the CoS values of packets, such as DSCP (Differentiated Services Code Point) or 802.1p bits, as they exit an interface.

- Rewrite rules can alter the class-of-service values in the packet headers to match the desired policies of the outbound interface.

- Therefore, rewrite rules are the correct component for altering CoS values on an outbound interface.

4. **Forwarding Classes**:

- Forwarding classes are used to categorize packets into different traffic classes within a router for QoS handling.

- They help in defining how packets should be treated by the scheduler but do not directly modify the CoS values.

**Conclusion**:

To alter class-of-service values in packets on the outbound interface of an edge router, the correct CoS component to use is:

**C. rewrite rules**

**References**:

- Juniper Networks Documentation on CoS: [Class of Service Overview](https://www.juniper.net/documentation/en_US/junos/topics/concept/class-of-service-overview.html)

- Junos OS CoS Configuration Guide: [Rewrite Rules](https://www.juniper.net/documentation/en_US/junos/topics/topic-map/class-of-service-rewrite-rules.html)

The problem in this scenario is that R1 and R8 are not receiving each other’s routes because of private AS numbers in the AS path. Private AS numbers are not globally unique and are not advertised to external BGP peers. To solve this problem, you need to do the following:

Configure loops on routers in AS 65412 and advertise-peer-as on routers in AS 64498. This allows R5 and R6 to advertise their own AS number (65412) instead of their peer’s AS number (64498) when sending updates to R7 and R8. This prevents a loop detection issue that would cause R7 and R8 to reject the routes from R5 and R62.

Configure remove-private on advertisements from AS 64497 toward AS 64498 and from AS 64500 toward AS 64499. This removes any private AS numbers from the AS path before sending updates to external BGP peers. This allows R2 and R3 to receive the routes from R1 and R4, respectively3.

The problem in this scenario is that CE-1 is configured with an incorrect peer AS number for its BGP session with PE-1. The CLI output shows that CE-1 is using AS 65531 as its local AS number and AS 65530 as its peer AS number. However, PE-1 is using AS 65530 as its local AS number and AS 65531 as its peer AS number. This causes a mismatch in the BGP OPEN messages and prevents the BGP session from being established. To solve this problem, CE-1 should configure its peer AS number as 65530 under [edit protocols bgp group external] hierarchy level.