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

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

In this scenario, you should create an aggregate route1. Aggregate routes are used for advertising summarized network prefixes1. 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 A is correct. Options B, C, and D are not correct because:

• Static route using the resolve feature: This type of route uses the resolve feature to install a static route in the routing table only if a specific condition is met1. However, it does not provide the capability to summarize multiple routes into a single prefix.
• Generate route: This type of route generates a route that is always present in the routing table and can be used to summarize routes. However, it does not have the capability to only advertise the route when specific BGP routes are being received from a neighbor1.
• Static route using qualified next hops: This type of route allows for the specification of multiple next-hop addresses for a static route1. However, it does not provide the capability to summarize multiple routes into a single prefix.

• C is correct because Layer 2 control traffic is permitted on the secondary link of a redundant trunk group (RTG) on EX Series switches. Layer 2 control traffic includes protocols such as LLDP, LACP, and STP, which are used to exchange information and coordinate actions between switches1. According to the Juniper Networks documentation2, Layer 2 control traffic is allowed to pass through both the active and the secondary links of an RTG, but data traffic is only forwarded through the active link. This allows the switches to maintain their Layer 2 adjacencies and monitor the link status on both links.
• D is correct because if the active link fails, then the secondary link automatically takes over in an RTG on EX Series switches. An RTG consists of two trunk links: an active or primary link, and a secondary or backup link2. The active link is used to forward data traffic, while the secondary link is in standby mode. If the active link fails or becomes unavailable, the secondary link immediately transitions to a forwarding state and takes over the data traffic without waiting for normal STP convergence2. This provides fast recovery and redundancy for the network.