Chapter 2: Basic switch concepts dfiti an d con fi gura ti ons CCNA Exploration 4.0 1 Overview Học viện mạng Bach Khoa - Website: www.bkacad.com 2 Ke y elements of y ethernet/802.3 network Học viện mạng Bach Khoa - Website: www.bkacad.com 3 Media Access Control (MAC) •MAC refers to protocols that determine which computer hd di logical bus topology and Deterministic, Non-Deterministic on a s h are d -me di um environment, or collision domain, is allowed to transmit the data topology and physical star or extended star transmit the data . •MAC, with LLC, comprises the IEEE version of the OSI Layer 2 logical ring topology and a Layer 2 •There are two broad categories of Media Access Control , deterministic ( takin g physical star topology , ( g turns) and non-deterministic (first come, first served) logical ring topology and physical dual ring Học viện mạng Bach Khoa - Website: www.bkacad.com 4 physical dual - ring topology CSMA/CD • CSMA/CD used with Ethernet performs three fti ??? f unc ti ons: 1. Transmitting and receiving data packets 2 Decoding data packets listen-before-transmit ??? 2 . Decoding data packets and checking them for valid addresses before passing them to the upper Transmitting& listening Why ??? passing them to the upper layers of the OSI model 3. Detecting errors within data p ackets or on the listening . Why ??? p network ??? Học viện mạng Bach Khoa - Website: www.bkacad.com 5 CSMA/CD Flow chart Học viện mạng Bach Khoa - Website: www.bkacad.com 6 Backoff •After a collision occurs and all stations allow the cable to become idle (each waits the Randomly Backoff Time become idle (each waits the full inter-frame spacing) •The stations that collided must wait an additional and must wait an additional and potentially progressively longer period of time before attem p tin g to retransmit the pg collided frame •The waiting period is intentionally designed to be random •If the MAC layer is unable to send the frame after sixteen attempts it gi es p and Học viện mạng Bach Khoa - Website: www.bkacad.com 7 attempts , it gi v es u p and generates an error to the network layer Ethernet Communications Học viện mạng Bach Khoa - Website: www.bkacad.com 8 Remind Layer 1: 802.3 Layer 2: 802.2 Học viện mạng Bach Khoa - Website: www.bkacad.com 9 Ethernet frame structure •At the data link layer the frame structure is nearly identical for all speeds of Ethernet from 10 all speeds of Ethernet from 10 Mbps to 10,000 Mbps •At the physical layer almost all versions of Ethernet are substantially different from one another with each speed having a distinct set of architecture design rules •The Ethernet II Type field is incorporated into the current 802 3 frame definition The 802 . 3 frame definition . The receiving node must determine which higher-layer protocol is present in an incoming frame Học viện mạng Bach Khoa - Website: www.bkacad.com 10 present in an incoming frame by examining the Length/Type field [...]... full-duplex mode • Default: when autonegotiation fails Catalyst switch sets the corresponding switch port to half-duplex mode Học viện mạng Bach Khoa - Website: www.bkacad.com 18 auto-MDIX • auto-MDIX is enabled switch auto detects cable type yp can use either a crossover or a straight-through • The auto-MDIX feature is enabled by default on switches running Cisco IOS Release 12.2(18)SE or later For releases... Bach Khoa - Website: www.bkacad.com 28 Broadcast Domains Học viện mạng Bach Khoa - Website: www.bkacad.com 29 Broadcast Domains - Example When a switch receives a broadcast frame, it forwards the frame to each of its ports, except the incoming port where the switch received the broadcast frame Each attached device recognizes the broadcast frame and processes it it Học viện mạng Bach Khoa - Website: www.bkacad.com... 12.2(18)SE or later For releases between Cisco IOS Release 12.1(14)EA1 and ( ) 12.2(18)SE, the auto-MDIX feature is disabled by default Học viện mạng Bach Khoa - Website: www.bkacad.com 19 MAC Addressing and Switch MAC Address Tables Học viện mạng Bach Khoa - Website: www.bkacad.com 20 Học viện mạng Bach Khoa - Website: www.bkacad.com 21 Học viện mạng Bach Khoa - Website: www.bkacad.com 22 Học viện mạng Bach . Chapter 2: Basic switch concepts dfiti an d con fi gura ti ons CCNA Exploration 4.0 1 Overview Học viện. • Default: when autonegotiation fails Æ Catalyst switch sets Default: when autonegotiation fails Æ Catalyst switch sets the corresponding switch port to half-duplex mode. Học viện mạng. 18 auto-MDIX • auto-MDIX is enabled switch auto detects cable t yp e Æ yp can use either a crossover or a straight-through • The auto-MDIX feature is enabled by default on switches running Cisco IOS