ECP-206 Exam Dumps : Ericsson Certified Associate - IP Networking

A BGP session is established between two routers by sending a unicast OPEN message. BGP uses TCP as its transport protocol, which means that before exchanging any BGP information, a TCP connection must be established between the routers. The TCP connection uses port 179 as both source and destination port. After establishing a TCP connection, each router sends an OPEN message to its neighbor, containing parameters such as BGP version number, AS number, hold time, BGP identifier, and optional capabilities. The OPEN message also serves as a keepalive message for BGP. If both routers agree on these parameters, they proceed to exchange UPDATE messages containing routing information and establish a BGP session.

A BGP router does not send a NOTIFICATION message to establish a session, but rather to terminate a session due to an error or a manual shutdown. A BGP router does not send a CONNECT message, as this is a TCP state, not a BGP message. A BGP router does not send a multicast HELLO packet, as this is an OSPF message, not a BGP message. References: BGP Neighbor States > BGP Fundamentals | Cisco Press, Demystifying BGP Session Establishments - Packet Pushers, The TCP/IP Guide - BGP Connection Establishment: Open Messages

Penultimate hop popping (PHP) is a function performed by certain routers in an MPLS enabled network. It refers to the process whereby the outermost label of an MPLS tagged packet is removed by a label switch router (LSR) before the packet is passed to an adjacent label edge router (LER). The purpose of PHP is to reduce the load on the LER, as it saves one cycle of label lookup. The LER can forward the packet based on its IP header or another label in the stack, without having to process the outer label. PHPfunctionality is achieved by the LER advertising a label with a value of 3 to its neighbors. This label is defined as "implicit-null" and informs the neighboring LSRs to perform PHP12.

References: Penultimate hop popping - Wikipedia, MPLS Penultimate hop popping - NetworkLessons.com

The route type that is restricted in an OSPF stub area is type 5. Type 5 LSAs are external LSAs that are generated by ASBRs to advertise routes from other routing domains or protocols into OSPF. Type 5 LSAs are flooded throughout the OSPF domain by default, except in stub areas. Stub areas are special OSPF areas that block type 5 LSAs from entering the area in order to reduce the size of the LSDB and the routing table. Stub areas only receive information about intra-area routes (type 1 and 2 LSAs), inter-area routes (type 3 LSAs), and a default route (type 3 LSA with destination 0.0.0.0/0) from the ABRs910.

References: Introduction to OSPF Stub Areas - NetworkLessons.com, What Are OSPF Areas and Virtual Links? - Cisco