Most Recent Juniper JN0-351 Exam Dumps

BFD is a protocol that can be used to quickly detect failures in the forwarding path between two adjacent routers or switches. BFD can be integrated with various routing protocols and link aggregation protocols to provide faster convergence and fault recovery.

According to the Juniper Networks documentation, the following protocols support BFD on Junos OS devices1:

BGP: BFD can be used to monitor the connectivity between BGP peers and trigger a session reset if a failure is detected.BFD can be configured for both internal and external BGP sessions, as well as for IPv4 and IPv6 address families2.

OSPF: BFD can be used to monitor the connectivity between OSPF neighbors and trigger a state change if a failure is detected.BFD can be configured for both OSPFv2 and OSPFv3 protocols, as well as for point-to-point and broadcast network types3.

LACP: BFD can be used to monitor the connectivity between LACP members and trigger a link state change if a failure is detected.BFD can be configured for both active and passive LACP modes, as well as for static and dynamic LAGs4.

Other protocols that support BFD on Junos OS devices are:

IS-IS: BFD can be used to monitor the connectivity between IS-IS neighbors and trigger a state change if a failure is detected. BFD can be configured for both level 1 and level 2 IS-IS adjacencies, as well as for point-to-point and broadcast network types.

RIP: BFD can be used to monitor the connectivity between RIP neighbors and trigger a route update if a failure is detected. BFD can be configured for both RIP version 1 and version 2 protocols, as well as for IPv4 and IPv6 address families.

VRRP: BFD can be used to monitor the connectivity between VRRP routers and trigger a priority change if a failure is detected. BFD can be configured for both VRRP version 2 and version 3 protocols, as well as for IPv4 and IPv6 address families.

The protocols that do not support BFD on Junos OS devices are:

RSTP: RSTP is a spanning tree protocol that provides loop prevention and rapid convergence in layer 2 networks. RSTP does not use BFD to detect link failures, but relies on its own hello mechanism that sends BPDU packets every 2 seconds by default.

FTP: FTP is an application layer protocol that is used to transfer files between hosts over a TCP connection. FTP does not use BFD to detect connection failures, but relies on TCP's own retransmission and timeout mechanisms.

1: [Configuring Bidirectional Forwarding Detection]2: [Configuring Bidirectional Forwarding Detection for BGP]3: [Configuring Bidirectional Forwarding Detection for OSPF]4: [Configuring Bidirectional Forwarding Detection for Link Aggregation Control Protocol] : [Configuring Bidirectional Forwarding Detection for IS-IS] : [Configuring Bidirectional Forwarding Detection for RIP] : [Configuring Bidirectional Forwarding Detection for VRRP] : [Understanding Rapid Spanning Tree Protocol] : [Understanding FTP]

Bis correct because the loops do not exist is one of the conditions that are verified by the receiving router to ensure that the received BGP route is valid.A loop in BGP means that a route has been advertised by the same AS more than once, which can cause routing instability and inefficiency1.To prevent loops, BGP uses the AS-path attribute, which lists the AS numbers that a route has traversed from the origin to the destination2.The receiving router checks the AS-path attribute of the received route and discards it if it finds its own AS number in the list2. This way, BGP avoids accepting routes that contain loops.

Cis correct because the next hop is reachable is one of the conditions that are verified by the receiving router to ensure that the received BGP route is valid.The next hop is the IP address of the next router that is used to forward packets to the destination network3.The receiving router checks the next hop attribute of the received route and verifies that it has a valid route to reach it3.If the next hop is not reachable, the received route is not usable and is rejected by the receiving router3. This way, BGP ensures that only feasible routes are accepted.

Option A is correct. For traffic to be sent through a GRE tunnel, there must be a route that directs the traffic into the tunnel. This is typically accomplished through the use of a static route or a dynamic routing protocol.

Option B is correct. All intermediary devices must have a route to the tunnel endpoints34. In real-world scenarios, the tunnel endpoints for a tunnel going over the Internet must have globally reachable internet addresses. Otherwise, intermediate routers in the Internet cannot forward the tunneled packets.

Ais correct because RSTP alternate ports block traffic while receiving superior BPDUs from a neighboring switch.An alternate port is a backup port for a root port, which means it receives better BPDUs from another bridge than the current root port1.However, an alternate port does not forward any traffic, as it is in a discarding state2. It only listens to BPDUs and waits for the root port to fail.If the root port fails, the alternate port can immediately transition to a forwarding state and become the new root port1.

Cis correct because RSTP alternate ports provide an alternate higher cost path to the root bridge.An alternate port is selected based on the same criteria as the root port, which are the lowest bridge ID, the lowest path cost, the lowest sender port ID, and the lowest receiver port ID3.However, an alternate port receives a higher cost BPDU than the root port, otherwise it would be the root port itself1. Therefore, an alternate port provides an alternate higher cost path to the root bridge than the root port.

Ais correct because dynamic ARP inspection (DAI) is a Layer 2 security feature that prevents ARP spoofing attacks. ARP spoofing is a technique that allows an attacker to send fake ARP messages to associate a spoofed MAC address with a legitimate IP address. This can result in traffic redirection, man-in-the-middle attacks, or denial-of-service attacks.DAI validates ARP packets by checking the source MAC address and IP address against a trusted database, which is usually built by DHCP snooping1.DAI discards any ARP packets that do not match the database or have invalid formats1.

Cis correct because DHCP snooping is a Layer 2 security feature that prevents DHCP spoofing attacks. DHCP spoofing is a technique that allows an attacker to act as a rogue DHCP server and offer fake IP addresses and other network parameters to unsuspecting clients. This can result in traffic redirection, man-in-the-middle attacks, or denial-of-service attacks. DHCP snooping filters DHCP messages by classifying switch ports as trusted or untrusted.Trusted ports are allowed to send and receive any DHCP messages, while untrusted ports are allowed to send only DHCP requests and receive only valid DHCP replies from trusted ports2.DHCP snooping also builds a database of MAC addresses, IP addresses, lease times, and binding types for each client2.