JN0-351 Exam Dumps : Enterprise Routing and Switching Specialist (JNCIS-ENT)

Redundant Trunk Groups (RTGs) on EX Series switches provide a simple solution for network recovery when a trunk port on a switch goes down 1 .  They are configured on the access switch and contain two links: a primary or active link, and a secondary link 1 .  Therefore, option B is correct because if the active link fails, the secondary link automatically starts forwarding data traffic without waiting for normal spanning-tree protocol convergence 1 .

Option D is also correct.  In a typical enterprise network composed of distribution and access layers, RTGs are used where one Access switch is connected to two different uplink switches 2 .  This implies that RTGs must be connected to the same aggregation switch 2 .

The DHCP snooping feature in Juniper Networks’ EX Series switches works by building a binding database that maps the IP address, MAC address, lease time, binding type, VLAN number, and interface information 1 .  This database is used to filter and validate DHCP messages from untrusted sources 1 .

However, there are certain conditions that could prevent entries from being automatically created in the snooping database for an interface:

MAC limiting: If MAC limiting is enabled on the interface, it could potentially interfere with the operation of DHCP snooping.  MAC limiting restricts the number of MAC addresses that can be learned on a physical interface to prevent MAC flooding attacks 1 . This could inadvertently limit the number of DHCP clients that can be learned on an interface, thus preventing new entries from being added to the DHCP snooping database.

Static IP address : If the device connected to the interface is configured with a static IP address, it will not go through the DHCP process and therefore will not have an entry in the DHCP snooping database 1 .  The DHCP snooping feature relies on monitoring DHCP messages to build its database 1 , so devices with static IP addresses that do not send DHCP messages will not have their information added.

Therefore, options B and C are correct.  Options A and D are not correct because performing a DHCPRELEASE would simply remove an existing entry from the database 1 , and Dynamic ARP inspection (DAI) uses the information stored in the DHCP snooping binding database but does not prevent entries from being created 1 .