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Flashcards

NatAcad 7: Ethernet Switching

Scott Jones CCNA IT Certification English 36 cards

Cards in this deck (36)

  1. 1What is the length of an Ethernet Frame? What is not included?64 - 1518 bytes.
    The Preamble and SFD fields are not included.
  2. 2What are the preamble and SFD fields used for?Synchronisation between sending node and receiving node. The first few bytes of the preamble signifies it is the start of frame.
  3. 3How many bytes is the SFD?1 byte
  4. 4The Type field identifies the L3PDU, how are they represented?Hexadecimal values.
  5. 5What is meant by padding the frame?Extra bits are added to the data field to ensure the frame meets the minimum size.
  6. 6What data link sublayer controls the network interface through software drivers?LLC
  7. 7What is the length of a MAC address?6 bytes (48 bits). Represented in 12 hexadecimal values, each digit is 4 bits.
  8. 8What is meant by a MAC address being burned-in?It is encoded onto the NIC ROM.
  9. 9When a host receives a frame, where does the computer retreive its MAC address to compare it to the destination.The ROM stores the MAC address in the RAM as the computer boots up.
  10. 10What is Address Resolution Protocol (ARP) used for?To determine the MAC address associated with the IPv4 address.
  11. 11When a sending device needs to determine the MAC address associated with the IPv6 address, what protocol does it use?Neighbour Discovery
  12. 12What is a unicast address?A single, unique address.
  13. 13What does a broadcast address do?It goes out to all devices and is received by all devices. It floods out all Ethernet switch ports except the incoming one.
  14. 14What does a MAC broadcast address look like?FF-FF-FF-FF-FF-FF
  15. 15What is this 11111111:11111111:11111111:11111111A DHCP IPv4 broadcast address which translates to 255:255:255:255
  16. 16What is DHCPDynamic Host Configuration Protocol
    It automatically assignes IP addresses to devices on the LAN.
  17. 17What does a multicast address do?It is received and processed by by a group of devices belonging to the same multicast group. Flooded out all switch ports besides the incoming.
  18. 18What makes an IPv4 multicast different from an IPv6?The destination MAC address will be different.
  19. 19Do routers forward multicasts and broadcasts?Nope, but they can be congifured to forward multicasts.
  20. 20Switches make forwarding decisions based on what factor?MAC addresses
  21. 21A switch gets a frame and looks up the MAC address in its MAC address table. The entry is already known, what happens to the entry in the table?It updates the refresh timer for the entry.
  22. 22What is an unknown unicast?It is when the switch does not know the address. It will flood the frame out all its other ports.
  23. 23Why can switches have more than one address associated with one port?It is because there are other addresses associated with that port. For example, a switch connecting to another switch.
  24. 24Name the two forwarding methods Cisco switches use.Store-and-forward switching
    Cut-through switching
  25. 25What is the cyclic redundancy check (CRC)?It is part of the FCS field. A calculation is performed on the frame to get a value. The value is used for error checking.
  26. 26What is store-and-forward switching?A forwarding method where the switch performs a CRC check on the frame it receives. If there are errors, the frame is discarded, this will also reduce network bandwidth.
  27. 27What is cut-through switching?A forwarding method where the frame is sent before it is full received. No error checking is performed. It is useful for QoS analysis to prioritise traffic.
  28. 28What is fast-forward switching?A variant of cut-through switching. This is fast and has low latency, it is forwarded as soon as the destination address is read.
  29. 29What is fragment-free switching?A variant of cut-through switching. The first 64 bytes of the frame are stored, and error checked before the entire frame is forwarded.
  30. 30What is meant by buffering frame?They are stored in memory before being forwarded; this is typically when the destination port is congested.
  31. 31Memory Buffering: What is port-based memory?The frames are stored in queues and transmitted sequentially. This can cause delays when the frame at the front cant transmit but the others in the queue have a destination port that is not busy.
  32. 32Memory Buffering: What is shared memory?All ports share memory and are linked to the destination port. Memory is dynamically allocated to ports.
  33. 33What is asymmetric switching?It is when you can have varied data rates on different ports.
  34. 34What is autonegotiation?An optional function on switches that enables them to automatically negotiate the most appropriate speed and duplex settings.
  35. 35What is this 01-00-5E?The value assigned to the first 24 bits of a multicast MAC address with an IPv4 packet.
  36. 36You see a MAC address beginning with 33-33. What does it mean?It is a multicast MAC address with an IPv6 packet being transmitted.

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IT Certification CCNA Flashcards on NatAcad 7: Ethernet Switching, created by Scott Jones on 19/10/2022.
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Scott Jones
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