ethernet switching TEMA 7 CCNA 1 v7.0
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ETHERNET is a layer 2 and layer 3 protocol
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IEEE 802.2 standar at protocol
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802.3 standards at protocol
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FIJATE la sintaxis de la IEEE pata las diferentes standar, que son todos 802.2 xxxx
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The minimum Ethernet frame size is XXXX bytes and the expected maximum is 1518 bytes
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The minimum Ethernet frame size is 64 bytes and the expected maximum is XXXX bytes
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what happends at the receiving device if the size of a transmitted frame is less than the minimum, or greater than the maximum?
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also called the Start of Frame (1 byte), fields are used for synchronization between the sending and receiving devices. These first eight bytes of the frame are used to get the attention of the receiving nodes. Essentially, the first few bytes tell the receivers to get ready to receive a new frame.
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This 6-byte field is the identifier for the intended recipient. As you will recall, this address is used by Layer 2 to assist devices in determining if a frame is addressed to them. . If there is a match, the device accepts the frame. Can be a unicast, multicast or broadcast address.
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This 6-byte field identifies the originating NIC or interface of the frame.
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This 2-byte field identifies the upper layer protocol encapsulated in the Ethernet frame. Common values are, in hexadecimal, 0x800 for IPv4, 0x86DD for IPv6 and 0x806 for ARP. Note: You may also see this field referred to as EtherType, Type, or Length.
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This field (46 - 1500 bytes) contains the encapsulated data from a higher layer, which is a generic Layer 3 PDU, or more commonly, an IPv4 packet. All frames must be at least 64 bytes long. If a small packet is encapsulated, additional bits called a pad are used to increase the size of the frame to this minimum size.
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All frames must be at least 64 bytes long. Additional bits called a "pad" are used to increase the size ot small frames to the minimum size.
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The LLC sublayer is responsible tor controlling the network interface card through software drivers
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Which part of an Ethernet Frame notifies the receiver to get ready for a new frame?
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FIJATE EN EL TAMAÑO Y EN LA SECUENCIA
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ARP PROTOCOL : Address Resolution Protocol
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cuantos bit tiene una MAC ?
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cuantos bits tiene un digita hex ?
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cuantos digitos hex tiene una mac ?
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n an Ethernet LAN, every network device is connected to the same, shared media
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que parte de la mac identifica al venderor ?
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a burned-in address (BIA) is also named ?
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MAC address is referred to as a burned-in address (BIA) because the address is hard coded into XXXXXX on the NIC. This means that the address is encoded into the XXXXX chip permanently
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When the computer boots up, the NIC copies its MAC address from XXX into XXXX
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When a NIC receives an Ethernet frame, it examines the destination MAC address to see if it matches the physical MAC address that is stored in XXXX If there is no match, the device discards the frame. If there is a match, it passes the frame up the XXXXX , where the de-encapsulation process takes place.
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The source MAC address must always be ???
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The process that a source host uses to determine the destination MAC address associated with an IPv4 address is known as
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The process that a source host uses to determine the destination MAC address associated with an IPv6 address is known as
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192.168.1.255 and FF-FF-FF-FF-FF-FF ( FF= 1111 1111 ) are ??
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que ocurre si en un frame se indica IPv4 de destino 192.168.1.255 y como MAC de destino FF-FF-FF-FF-FF-FF ??
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MULTICAST There is a destination MAC address of XXXXX when the encapsulated data is an IPv4 multicast packet and a destination MAC address of XXXXX when the encapsulated data is an IPv6 multicast packet
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MULTICAST There are other reserved multicast destination MAC addresses for when the encapsulated data is not IP, such as Spanning Tree Protocol (STP) and Link Layer Discovery Protocol (LLDP).
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by default , a Ethernet switch will flooed out all ports included the incoming port in a multicast frame ?
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como tiene que estar configurado un router para forward multicast frames?
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224.0.0.0 hasta 239.255.255.255 ¿qué son ?
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una dirección ipv6 que comienza con ff00::/8 ¿qué indica?
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un rango de direcciones multicas, que represesta y como puede ser denominado ?
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que parte identifica al vendedor de una MAC y como puede ser denominado tambien este código ?
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111 1111 cuantos bits, bytes y cuantos digitos hexes de 1111 1111?
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why a A Layer 2 Ethernet switch uses Layer 2 MAC addresses table ?
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does a A Layer 2 Ethernet switch knows what type of data (protocol) is being carried in the data prtion of the frame, and then based in the data carriedm makes a forwarding decision?
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If the destination MAC address is not in the table, the switch will forward the frame out all ports except the incoming port. This is called ....
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Switch Learning and Forwarding
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Switch Learning and Forwarding
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cuando un SW se está construyendo una lista de mac addres , que ocurre al inicio ?
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, switches use their XXXX address tables to determine which port to use to forward frames
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With Cisco switches, there are actually two frame forwarding methods
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This frame forwarding method receives the entire frame and computes the CRC. CRC uses a mathematical formula, based on the number of bits (1s) in the frame, to determine whether the received frame has an error. If the CRC is valid, the switch looks up the destination address, which determines the outgoing interface. Then the frame is forwarded out of the correct port.
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This frame forwarding method forwards the frame before it is entirely received. At a minimum, the destination address of the frame must be read before the frame can be forwarded.
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A big advantage XXXXXX switching is that it determines if a frame has errors before propagating the frame. When an error is detected in a frame, the switch discards the frame
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Discarding frames with errors reduces the amount of bandwidth consumed by corrupt data
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xxxxxxx switching is required for quality of service (QoS) analysis on converged networks where frame classification for traffic prioritization is necessary. For example, voice over IP (VoIP) data streams need to have priority over web-browsing traffic.
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Antes de mirar la tabla de mac un cisco SW comprueba por errores en el frame
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the switch acts upon the data as soon as it is received, even if the transmission is not complete. The switch buffers just enough of the frame to read the destination MAC address so that it can determine to which port it should forward out the data. The destination MAC address is located in the first 6 bytes of the frame following the preamble. The switch looks up the destination MAC address in its switching table, determines the outgoing interface port, and forwards the frame onto its destination through the designated switch port. The switch does not perform any error checking on the frame.
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que método de frame forwarding buffer en memoria parte del frame para determinar la dirección de mac par poder enviarlo ?
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no hace ningún chequeo de error en frame al recbirlo
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This frame forwarding method receives the entire frame and computes the CRC. CRC uses a mathematical formula, based on the number of bits (1s) in the frame, to determine whether the received frame has an error. If the CRC is valid, the switch looks up the destination address
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Fast-forward switching and Fragment-free switching are two variants of
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Some switches are configured to perform cut-through switching on a per-port basis until a user-defined error threshold is reached, and then they automatically change to store-and-forward. When the error rate falls below the threshold, the port automatically changes back to cut-through switching.
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XXXXXXXX offers the lowest level of latency. Fast-forward switching immediately forwards a packet after reading the destination address. Because XXXXXXX switching starts forwarding before the entire packet has been received, there may be times when packets are relayed with errors XXXXX is the typical cut-through method of switching
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XXXXX is the typical cut-through method of switching
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switch stores the first 64 bytes of the frame before forwarding. The reason XXXXX switching stores only the first 64 bytes of the frame is that most network errors and collisions occur during the first 64 bytes. XXXXX switching tries to enhance fast-forward switching by performing a small error check on the first
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XXXXXX switching is a compromise between the high latency and high integrity of store-and-forward switching, and the low latency and reduced integrity of fast-forward switching.
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Memory Buffering Methods |||||| Port-based memory
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Memory Buffering Methods ||||| Shared memory
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This is important with asymmetric switching which allows for different data rates on different ports such as when connecting a server to a 10 Gbps switch port and PCs to 1 Gbps ports.
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optional function found on most Ethernet switches and NICs. It enables two devices to automatically negotiate the best speed and duplex capabilities.
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Autonegotiation ::: Full-duplex is chosen if both devices have the capability along with their highest common bandwidth
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fijate acerca de evitar duplex missmatch
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Most switch devices now support the automatic medium-dependent interface crossover (auto-MDIX) feature. When enabled, the switch automatically detects the type of cable attached to the port and configures the interfaces accordingly
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The auto-MDIX feature is enabled by default on switches running Cisco IOS Release 12.2(18)SE or later
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you should always use the correct cable type and not rely on the auto-MDIX feature ¿why ?
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Auto-MDIX can be re-enabled using the mdix auto interface configuration command.
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correct cable type required to interconnect switch-to-switch, switch-to-router, switch-to-host, or router-to-host devices
Explicación
MAC Sublayer - This sublayer (IEEE 802.3, 802.11, or 802.15 for example) |||||| LLC Sublayer - This IEEE 802.2
1111 1111 son 8 bites |||||| 4 bites son 1 BYTE |||||| 1 hex digit equivale a 1 BYTE |||||| por lo tanto |||||| tenemos 8 bites, 4 bites y 2 dígitos hexes
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