ccna multiple questions

ccna multiple questions.Length (16 bits): used to indicate the length of the load in the PPPoE packet. 6Load: also known as the data field, the data content of this field can vary significantly at different stages of PPPoE. During the discovery phase of PPPoE, this field is populated with some tokens; while during the session phase of PPPoE, this field carries the data of the PPP.Chapter 19 Branch Connectivity . 355 .193 Overview of Tunneling Technology19.3.1 Introduction to GREGRE (GenericRoutingEncapsulation) was first proposed by Cisco, and it is now a standard, defined in RFC1701, RFC1702, RFC2784>RFC2890. RFC2890 is based on an enhanced version of RFC2784, and the latest version of CiscoIOS software uses RFC2890. GRE is an encapsulation protocol that defines how one network protocol can be used to encapsulate another network protocol. GRE belongs to the Layer 3 tunneling (Timnel) protocol for VPNs. by tunneling, we mean the entire process including data encapsulation, transmission, and decapsulation. GRE only provides packet encapsulation, it does not have encryption to prevent network eavesdropping and attacks, so in practice it is often used in conjunction with IPSec, which provides security and integrity of user data. For example, GRE can encapsulate multicast data (such as OSPF, EIGRP, video, and VoIP) and transmit it in a GRE tunnel, whereas IPSec can currently only encrypt and protect unicast data. For cases where multicast data needs to be transmitted in IPSec tunnels, GRE tunnels can be established first to encapsulate the multicast data in GRE, and then the encapsulated data can be encrypted in IPSec, thus achieving encrypted transmission of multicast data in IPSec tunnels. The main application of GRE is to carry IP as well as non-IP data in IP networks, and GRE features are described below.1 GRE is a stateless protocol and does not provide traffic control. 2 GRE adds at least 24 bytes of overhead, including a 20-byte IPv4 header and a 4-byte GRE header without any additional options.GRE is multiprotocol and can encapsulate IP as well as non-IP data within a tunnel.GRE allows multicast traffic and dynamic routing protocol packets to traverse the tunnel.The security features of GRE are relatively weak.