JNCIP-SP JN0-664 Exam Questions and Answers PDF

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.

IS-IS supports two levels of routing: Level 1 (intra-area) and Level 2 (interarea). An IS-IS router can be either Level 1 only, Level 2 only, or both Level 1 and Level 2. A router that is both Level 1 and Level 2 is called a Level 1-2 router. A Level 1-2 router sends separate hello messages for each level on both point-to-point and broadcast interfaces1. A point-to-point interface provides a connection between a single source and a single destination. A broadcast interface behaves as if the router is connected to a LAN.

IS-IS is a link-state routing protocol that uses the Dijkstra algorithm to compute the shortest paths between nodes in a network. The Dijkstra algorithm maintains three data structures: a tree database, a candidate database, and a link-state database (LSDB). The tree database contains the nodes that have been visited and their shortest distances from the source node. The candidate database contains the nodes that have not been visited yet and their tentative distances from the source node. The LSDB contains the topology information of the network, such as the links and their costs.

The Dijkstra algorithm works as follows:

The local router moves its own local tuples into the tree database. A tuple consists of a node ID, a distance, and a parent node ID. The local router’s tuple has a distance of zero and no parent node.

The local router moves its neighbors’ tuples into the candidate database. The neighbors’ tuples have distances equal to the costs of the links to them and parent node IDs equal to the local router’s node ID.

The local router selects the tuple with the lowest distance from the candidate database and moves it to the tree database. This tuple becomes the current node.

The local router updates the distances of the current node’s neighbors in the candidate database by adding the current node’s distance to the link costs. If a shorter distance is found, the parent node ID is also updated.

The algorithm repeats steps 3 and 4 until either the destination node is reached or the candidate database is empty.

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)