Juniper Updated JN0-351 Exam Questions and Answers by effy

B  is correct because duplex and speed settings are required to match on both participating devices.  According to the Juniper Networks documentation 1 , all the interfaces in a LAG must have the same speed and be in full-duplex mode. This ensures that the LAG can operate as a single logical link without any performance or compatibility issues.

C  is correct because member links are not required to be contiguous ports.  According to the Juniper Networks documentation 2 , you can group any Ethernet interfaces on a switch into a LAG, regardless of their physical location or slot number. This provides flexibility and scalability for configuring LAGs on switches.

A firewall filter is a configuration that defines the rules that determine whether to forward or discard packets at specific processing points in the packet flow. A firewall filter can also modify the attributes of the packets, such as priority, marking, or logging.  A firewall filter can be applied to various interfaces, protocols, or routing instances on a Juniper device 1 .

A firewall filter has a family attribute, which specifies the type of traffic that the filter can evaluate.  The family attribute can be one of the following: inet, inet6, mpls, vpls, iso, or ethernet-switching 2 . The family inet firewall filter is used to evaluate IPv4 traffic, which is the most common type of Layer 3 traffic on a network.

To create a family inet firewall filter, you need to specify the appropriate match criteria and actions for each term in the filter. The match criteria can include various fields in the IPv4 header, such as source address, destination address, protocol, port number, or DSCP value.  The actions can include accept, discard, reject, count, log, policer, or next term 3 .

To apply a firewall filter to Layer 3 traffic that is being sent between VLANs, you need to apply the filter to the appropriate IRB interface. An IRB interface is an integrated routing and bridging interface that provides Layer 3 functionality for a VLAN on a Juniper device. An IRB interface has an IP address that acts as the default gateway for the hosts in the VLAN.  An IRB interface can also participate in routing protocols and forward packets to other VLANs or networks 4 .

Therefore, option C is correct, because you should create a family inet firewall filter with the appropriate match criteria and actions. Option D is correct, because you should apply the firewall filter to the appropriate IRB interface.

Option A is incorrect, because you should not create a family ethernet-switching firewall filter with the appropriate match criteria and actions. A family ethernet-switching firewall filter is used to evaluate Layer 2 traffic on a Juniper device.  A family ethernet-switching firewall filter can only match on MAC addresses or VLAN IDs, not on IP addresses or protocols 5 .

Option B is incorrect, because you should not apply the firewall filter to the appropriate VLAN. A VLAN is a logical grouping of hosts that share the same broadcast domain on a Layer 2 network. A VLAN does not have an IP address or routing capability.  A firewall filter cannot be applied directly to a VLAN; it must be applied to an interface that belongs to or connects to the VLAN 6 .

Aggregate routes are used for advertising summarized network prefixes 1 2 .  They help minimize the number of routing tables in an IP network by consolidating selected multiple routes into a single route advertisement 1 .  This approach is in contrast to non-aggregation routing, in which every routing table contains a unique entry for each route 1 .

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 protocols 1 .

Aggregate routes are not automatically generated for all of the subnets in a routing table.  They need to be manually configured 1 .

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 route 1 .