Juniper JN0-351 Exam With Confidence Using Practice Dumps

Junos devices support various types of tunnels for different purposes12.

• Option B is correct. Generic Routing Encapsulation (GRE) is a tunneling protocol that can encapsulate a wide variety of network layer protocols inside virtual point-to-point links over an Internet Protocol network1. Junos devices support GRE tunnels1.
• Option D is correct. IPsec (Internet Protocol Security) is a protocol suite for securing Internet Protocol (IP) communications by authenticating and encrypting each IP packet of a communication session1. Junos devices support IPsec tunnels1.
• Option A is incorrect. Spanning Tree Protocol (STP) is not a type of tunnel. It’s a network protocol designed to prevent loops in a bridged Ethernet local area network2.
• Option C is incorrect. While Junos devices do support IP-IP (also known as IP tunneling), it’s not supported on all Junos devices1.

• The exhibit shows the configuration of BFD liveness detection for BGP at the global level, which applies to all BGP neighbors by default1. However, this configuration does not specify the session mode, which determines whether BFD uses single-hop or multihop mode to communicate with a neighbor2.
• For single-hop BGP neighbors, which are directly connected on the same subnet, the session mode can be either automatic or single-hop. For multihop BGPneighbors, which are not directly connected and require multiple hops to reach, the session mode must be multihop2.
• Since your BGP neighbors are in different countries, they are likely to be multihop neighbors. Therefore, you need to configure the session mode as multihop for each neighbor individually at the [edit protocols bgp group group-name neighbor address bfd-liveness-detection] hierarchy level2. For example:

protocols { bgp { group usa { neighbor 192.0.2.1 { bfd-liveness-detection { session-mode multihop; } } } group france { neighbor 198.51.100.1 { bfd-liveness-detection { session-mode multihop; } } } } }

• If you do not configure the session mode for multihop neighbors, BFD will use the default mode of automatic, which will try to use single-hop mode and fail to establish a BFD session with the remote neighbor2. This will prevent BGP from using BFD to detect liveliness and failover.
• Therefore, the answer B is correct, as you need to configure the BFD liveness detection on the BGP neighbor level with the appropriate session mode for multihop neighbors.

IP-IP tunnels are a type of tunnels that use IP as both the encapsulating and encapsulated protocol. IP-IP tunnels are simple and easy to configure, but they do not provide any security or authentication features. IP-IP tunnels only support encapsulating IP traffic, which means that the payload of the inner packet must be an IP packet. IP-IP tunnels cannot encapsulate non-IP traffic, such as Ethernet frames or MPLS labels1.

Option A is correct, because IP-IP tunnels only support encapsulating IP traffic. Option B is incorrect, because IP-IP tunnels only support encapsulating non-IP traffic. Option C is incorrect, because the TTL in the inner packet is not decremented during transit to the tunnel endpoint. The TTL in the outer packet is decremented by each router along the path, but the TTL in the inner packet is preserved until it reaches the tunnel endpoint2. Option D is incorrect, because there are 20 bytes of overhead with IP-IP encapsulation. The overhead consists of the header of the outer packet, which has a fixed size of 20 bytes for IPv43.

References:

1: IP-IP Tunneling 2: What is tunneling? | Tunneling in networking 3: IPv4 - Header