ccna dummies pdf

ccna dummies pdf.Network device discovery, maintenance, and management is one of the important tasks of a network administrator. This chapter covers device discovery protocols CDP and LLDP, NTP and log maintenance, router and switch file systems, IOS maintenance, and router and switch password recovery.12.1 Overview of CDP and LLDP12.1.1 Introduction to CDPCDP (CiscoDiscoveryProtocol) is a Cisco proprietary protocol that enables Cisco network devices to discover other Cisco devices that are adjacent and directly connected. CDP is a data link layer protocol, and CDP messages are Ethernet IEEE 802.3 SNAP frames (with a protocol ID field value of 0x2000), sent as multicasts (multicast destination MAC addresses are 01-00-0c-cc-cc-cc), so Cisco devices using different network layer protocols can also obtain information about each other. The Cisco device's CDP function is enabled by default and sends CDP announcements every 60 seconds, which contain basic information about itself, including host name, hardware model, software version, CDP announcement maintenance time (180 seconds by default), and relevant interface identification, etc. The neighboring devices will save it in their own CDP neighbor table after receiving it.12.1.2 Introduction to LLDPLLDP (LinkLayerDiscoveryProtocol) is a Layer 2 protocol defined in IEEE802.lab, which provides a standard way of link layer discovery, LLDP messages Ethernet II frames (type field value 0x88CC) or Ethernet IEEE 802.3 SNAP frames (protocol ID field value 0x88CC) to The LLDP message Ethernet II frame (type field value 0x88CC) or Ethernet IEEE 802.3 SNAP frame (protocol ID field value 0x88CC) is sent as a multicast (multicast destination MAC address 0180.c200.000e), which can organize the primary capability, management address, device identity, interface identity, etc. of this device into different TLVs (Type/Length/Value) and encapsulate them in LLDPDUs (LLDPDUs). LinkLayerDiscovery ProtocolDataUnit) and send it to the directly connected neighbors, who receive the information and store it in the form of standard MIB (ManagementInfonnationBase) for the network management system to query and To determine the communication status of the link. The LLDP feature is disabled by default on the Cisco device, and when enabled, the Cisco device sends LLDP announcements every 30 seconds by default, and the LLDP announcement maintenance time is 120 seconds by default.12.2 Overview of NTP and System Logging12.2.1 Introduction to NTP Using accurate time on network devices enables administrators to use the correct timestamp to accurately track such things as security violations.166.Cisco Networking Lab CCNA Lab Guide (Version 2)regulation and other network events, correctly interpret events and digital certificates in system log data, and troubleshoot the network in a timely and accurate manner. NTP (NetworkTimeProtocol, Network Time Protocol) is a protocol used to synchronize computer system clocks. NTP works on port UDP123. NTP enables network devices to synchronize their time settings with an NTP server, ensuring greater consistency in the time settings of NTP clients that obtain time and date information from a single source.