Juniper Updated JN0-351 Exam Questions and Answers by aminah

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 .

In OSPF, the state of the neighbor relationship is determined by the exchange of OSPF packets between routers 1 .  The state “2Way” as shown in the exhibit indicates that bi-directional communication has been established between the two OSPF routers 1 .  This is the normal state for a neighbor that is not the Designated Router (DR) or Backup Designated Router (BDR) on a broadcast, non-broadcast multi-access (NBMA), or point-to-multipoint network 1 .  These neighbors are often referred to as " DRothers " 1 . Therefore, option B is correct.

The default MAC age-out timer on an EX Series switch is 300 seconds 1 2 .  The MAC age-out timer is the maximum time that an entry can remain in the MAC table before it “ages out,” or is removed 3 1 .  This configuration can influence efficiency of network resource use by affecting the amount of traffic that is flooded to all interfaces 1 .  When traffic is received for MAC addresses no longer in the Ethernet routing table, the router floods the traffic to all interfaces 1 .

Default BGP keepalive timer in Junos is 30 seconds

The default keepalive time for BGP is 30 seconds, which means that BGP peers send keepalive messages to each other every 30 seconds to verify the liveness of the BGP session. If no keepalive message is received from a peer within the hold time, which is 90 seconds by default, the peer is considered to be unavailable and the BGP session is closed. The keepalive time and the hold time can be configured manually for each BGP peer or peer group, but they must match on both ends of the BGP session. The keepalive time should be one third of the hold time for optimal performance. Therefore, option C is correct and the other options are incorrect. References:  BGP keepalive messages and hold time - Juniper Networks