Juniper JN0-351 - Enterprise Routing and Switching Specialist (JNCIS-ENT)

BGP attributes are properties that BGP uses for route advertisement, path selection, and loop prevention1. There are four categories of BGP attributes123:

Well-known mandatory: Must be recognized by all BGP routers, present in all BGP updates, and passed on to other BGP routers123.

Well-known discretionary: Supported by all BGP implementations, and are optionally included in BGP updates1.

Optional transitive: May not be supported by all implementations of BGP1.

Optional non-transitive: May not be supported by all implementations of BGP1.

The well-known mandatory attributes must be supported by all BGP implementations and must be included in every update123. These include the AS path and next hop attributes23. Therefore, options A and C are correct.

Aggregate routes are used for advertising summarized network prefixes12. They help minimize the number of routing tables in an IP network by consolidating selected multiple routes into a single route advertisement1. This approach is in contrast to non-aggregation routing, in which every routing table contains a unique entry for each route1.

Therefore, option D is correct. Options A, B, and C are not correct because:

Aggregate routes can be used with both static routing and dynamic routing protocols1.

Aggregate routes are not automatically generated for all of the subnets in a routing table. They need to be manually configured1.

Aggregate routes are not always preferred over more specific routes. The route selection process in Junos OS considers several factors, including route preference and metric, before determining the active route1.

The management IP address of a device is the IP address that is used to access the device for configuration and monitoring purposes. It is usually assigned to a dedicatedmanagement interface that is separate from the data interfaces. The management interface can be accessed via SSH, Telnet, HTTP, or other protocols.

In the exhibit, the list of interfaces and their statuses shows that the management interface isme0. This interface has an admin status ofup, a protocol status ofinet, a local address of172.23.12.100/24, and a remote address ofunspecified. This means that the me0 interface is active, has an IPv4 address assigned, and is not connected to another device.

Therefore, the management IP address of the device shown in the exhibit is172.23.12.100.

References:

[Management Interfaces Overview] : [Displaying Interface Status Information]

The exhibit shows the configuration of RSTP on EX-4, which has the command force-version stp. This command forces the switch to use the legacy STP protocol instead of RSTP, even though the switch supports RSTP1. This means that EX-4 will not be able to take advantage of the faster convergence and enhanced features of RSTP, such as edge ports, link type, and proposal/agreement sequence2.

The other switches in the network are likely to be running RSTP, as it is the default protocol for EX Series switches3. Therefore, there will be a compatibility issue between EX-4 and the other switches, which will result in longer convergence times and suboptimal performance. The switch will also generate a warning message that says “Warning: STP version mismatch with neighbor” when it receives a BPDU from a RSTP neighbor1.

To solve this problem, the force-version command must be removed from EX-4, so that it can run RSTP natively and interoperate with the other switches in the network. This will enable faster convergence and better stability for the network topology. To remove the command, you can use the delete protocols rstp force-version command in configuration mode1.

A RIB group is a configuration that allows a routing protocol to install routes into multiple routing tables in Junos OS. A RIB group consists of an import-rib statement,which specifies the source routing table, and an export-rib statement, which specifies the destination routing table or group. A RIB group can also include an import-policy statement, which specifies one or more policies to control which routes are imported into the destination routing table or group1.

An import policy is a policy statement that defines the criteria for accepting or rejecting routes from the source routing table. An import policy can also modify the attributes of the imported routes, such as preference, metric, or community. An import policy can be applied to a RIB group by using the import-policy statement under the [edit routing-options rib-groups] hierarchy level1.

Therefore, option A is correct, because an import policy is applied to the RIB group to control which routes are installed in the destination routing table or group. Option B is incorrect, because all routes in the source routing table are imported into the destination routing table or group, unless filtered by an import policy. Option C is incorrect, because a firewall filter is not used to install routes in the RIB groups; a firewall filter is used to filter packets based on various criteria. Option D is incorrect, because an export policy is not applied to the RIB group; an export policy is applied to a routing protocol to control which routes are advertised to other devices.

References:

1: rib-groups | Junos OS | Juniper Networks

In BGP, routing policies are used to control the flow of routing information between BGP peers1.

Option C suggests that import policies are applied after the RIB-In table. This is correct because import policies in BGP are applied to routes that are received from a BGP peer, before they are installed in the local BGP Routing Information Base (RIB-In)1. The RIB-In is a database that stores all the routes that are received from all peers1.

Option D suggests that export policies are applied after the RIB-Local table. This is correct because export policies in BGP are applied to routes that are being advertised to a BGP peer, after they have been selected from the local BGP Routing Information Base (RIB-Local)1. The RIB-Local is a database that stores all the routes that the local router is using1.

Therefore, options C and D are correct.

Option A suggests that the MTU is not at least 1492 bytes. This is correct because IS-IS requires a minimum MTU of 1492 bytes to establish adjacencies1. If the MTU is less than this, IS-IS adjacencies will not be established1.

Option D suggests that the lo0 interface is not included as an IS-IS interface. This is also correct because the loopback interface (lo0) is typically used as the router ID in IS-IS1. If the loopback interface is not included in IS-IS, it could prevent IS-IS adjacencies from being established1.

Therefore, options A and D are correct.

Option A is correct. The storm control feature is enabled in the factory-default configuration on EX Series switches12. On EX2200, EX3200, EX3300, EX4200, and EX6200 switches, the factory default configuration enables storm control for broadcast and unknown unicast traffic on all switch interfaces2. On EX4300 switches, the factory default configuration enables storm control on all Layer 2 switch interfaces1.

Option B is incorrect. The storm control feature does not require a special license on EX Series switches34.

Option C is incorrect. There’s no information available that suggests the storm control feature is not supported on aggregate Ethernet interfaces.

Option D is incorrect. The storm control configuration applies to traffic at the ingress of an interface5, not just between the forwarding and control plane.

A is correct because you need to configure BGP multihop to enable redundancy for the EBGP peering between the two routers. BGP multihop is a feature that allows BGP peers to establish a session over multiple hops, instead of requiring them to be directly connected1. By default, EBGP peers use a time-to-live (TTL) value of 1 for their packets, which means that they can only reach adjacent neighbors1. However, if you configure BGP multihop with a higher TTL value, you can allow EBGP peers to communicate over multiple routers in between1. This can provide redundancy in case of a link failure or a router failure between the EBGP peers.

B is correct because you need to configure loopback interface peering to enable redundancy for the EBGP peering between the two routers. Loopback interface peering is a technique that uses loopback interfaces as the source and destination addresses for BGP sessions, instead of physical interfaces2. Loopback interfaces are virtual interfaces that are always up andreachable as long as the router is operational2. By using loopback interface peering, you can avoid the dependency on a single physical interface or link for the BGP session, and use multiple paths to reach the loopback address of the peer2. This can provide redundancy and load balancing for the EBGP peering.

C is correct because you need to configure routes for the peer loopback interface IP addresses to enable redundancy for the EBGP peering between the two routers. Routes for the peer loopback interface IP addresses are necessary to ensure that the routers can reach each other’s loopback addresses over multiple hops2. You can use static routes or dynamic routing protocols to advertise and learn the routes for the peer loopback interface IP addresses2. Without these routes, the routers will not be able to establish or maintain the BGP session using their loopback interfaces.