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]

Option A is correct.The storm control feature is enabled in the factory-default configuration on EX Series switches12.On EX2200, EX3200, EX3300, EX4200, and EX6200 switches, the factory default configuration enables storm control for broadcast and unknown unicast traffic on all switch interfaces2.On EX4300 switches, the factory default configuration enables storm control on all Layer 2 switch interfaces1.

Option B is incorrect.The storm control feature does not require a special license on EX Series switches34.

Option C is incorrect. There's no information available that suggests the storm control feature is not supported on aggregate Ethernet interfaces.

Option D is incorrect.The storm control configuration applies to traffic at the ingress of an interface5, not just between the forwarding and control plane.

In a Rapid Spanning Tree Protocol (RSTP) topology, the root bridge is determined by the switch with the lowest bridge priority value12.If all switches have the same priority, then the root bridge is assigned to the switch whose MAC address's hex value is the lowest2.The default bridge priority value is 3276832. However, without the actual exhibit, it's difficult to definitively determine which device is the root bridge.But based on the options provided, if we assume that the local device has a lower bridge priority or a lower MAC address than other devices in the network, then it could be considered as the root bridge for this RSTP topology45.

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.

BGP (Border Gateway Protocol) is a protocol designed to exchange routing and reachability information among autonomous systems (AS) on the internet1.

Option A is correct.When an EBGP router advertises routes to its neighbors, it appends its AS number to the AS_PATH attribute1.This is a key mechanism in BGP to prevent routing loops1.

Option C is correct.BGP has a built-in loop prevention mechanism whereby if a BGP router detects its own AS in the AS_PATH attribute, it will drop the prefix and will not continue to advertise it2.This helps to prevent routing loops2.

Option B is incorrect.EBGP routers do not accept routes that contain their own AS number in the AS_PATH2.Instead, they drop such routes as part of the loop prevention mechanism2.

Option D is incorrect.While it's true that EBGP routers append their AS number when advertising routes, they do not prepend their AS number1.The term ''prepend'' in BGP usually refers to a technique used to influence path selection by artificially lengthening the AS_PATH3.