Logical link control sub layer llc 8022 manages

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Logical Link Control sub layer (LLC) 802.2: manages communications between devices over a single link on a network. Uses Service Access Points (SAPs) to help lower layers talk to the Network Layer. Media Access Control (MAC) 802.3: builds frames from the 1’s and 0’s that the Physical Layer (address = 6-byte/48 bit) picks up from the wire as a digital signal and runs a Cyclic Redundancy Check (CRC) to assure no bits were lost or corrupted. 1. Physical Layer Puts data onto the wire and takes it off, physical layer specifications such as the connectors, voltage, physical data rates and DTE/DCE interfaces. Some common implementations include Ethernet/IEEE 802.3, Fast Ethernet, and Token Ring/IEEE 802.5. Cisco Hierarchical Model Core Layer purpose is to switch traffic as quickly as possible. Fast transport to enterprise services (internet etc). No packet manipulation, VLANs, access-lists. High-speed access required such as FDDI, ATM. Distribution Layer time sensitive manipulation such as routing, filtering and WAN access. Broadcast/ Multicast, media translations, security. Access Layer switches and routers, segmentation occurs here and workgroup access. Static (not dynamic) routing. 5
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Cisco CCENT Cram Guide v3.0 © Paul Browning 2017 TCP/IP Port Numbers These are used to connect to various services and applications and piggy back onto IP addresses. Common port numbers you should know include: 20 - File Transfer Protocol Data (TCP) 21 - File Transfer Protocol Control (TCP) (Listens on this port) 22 - SSH (TCP) 23 - Telnet (TCP) 25 - Simple Mail Transfer Protocol (TCP) 53 - Domain Name Service (TCP/UDP) 69 - Trivial File Transfer Protocol (UDP) 80 - HTTP/WWW (TCP) 110 - Post Office Protocol 3 (TCP) 119 - Network News Transfer Protocol (TCP) 123 - Network Time Protocol (UDP) 161/162 - Simple Network Management Protocol (UDP) 443 - HTTP over Secure Sockets Layer (HTTPS) (TCP) TCP (protocol 6) reliable, sequenced connection-oriented delivery, 20-byte header. UDP (protocol 17) connectionless, unsequenced best effort delivery, 8-byte header. Sends data but does not check to see if it is received. Telnet used to connect to a remote device (TCP). A password and username are required to connect. Telnet tests all seven layers of the OSI model. FTP connection orientated (TCP) protocol used to transfer large files. TFTP connectionless (UDP) protocol used for file transfer. SNMP allows remote management of network devices. ICMP supports packets containing error, control and informational messages. Ping uses ICMP to test network connectivity. Traceroute also uses ICMP. As with ping, Cisco routers allow you to perform an extended traceroute command that can define a number of associated parameters, most of them similar to the ping-related parameters: 6 Router#traceroute Protocol [ip]: Target IP address: 192.168.1.1 Source address: 10.10.10.2 Numeric display [n]: Timeout in seconds [3]: Probe count [3]: Minimum Time to Live [1]: Maximum Time to Live [30]:
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© Paul Browning 2017 Cisco CCENT Cram Guide v3.0 ARP used to map an IP address to a physical (MAC) address. A host wishing to obtain a physical address broadcasts an ARP request onto the TCP/IP network. The host replies with its physical
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