Networking Chapter 5

What is the minimum and maximum Ethernet frame size?

64-1518 bytes

Auto-MDIX

A feature that is enable on the latest Cisco switches and that allows the switch to detect and use whatever type of cable is attached to a specific port.

How does a switch to build its MAC address table?

By inspecting incoming layer 2 frames and recording the source MAC address found in the frame header. The discovered and recorded MAC address is then associated with the port used to receive the frame.

Explain port-based memory buffering

On a Cisco switch, this is used to buffer frames in queues linked to specific incoming and outgoing ports.

What are potential network problems that can result from ARP operation?

On large networks with low bandwidth, multiple ARP broadcasts could cause communication delays. Network attackers could manipulate MAC address and IP address mapping in the ARP messages with the intent of intercepting network traffic.

When sending data to a device on a remote network, the Ethernet frame uses what MAC address?

That of the default gateway.

Runt

a frame less than 64 bytes in length, usually caused by a collision or a network interface failure

Giants (Jumbo)

a frame that is greater than 1500 bytes

Describe MAC address

a globally unique 48 bit, or 6 bytes, address given to each device. The first 3 bytes are used for vendor identification and the last 3 must be assigned a unique value within the same OUI

cut-through

can forward frames before receiving the destination address field.

Describe features of the LLC sublayer.

is implemented in software and enables the data link layer to communicate with the upper layers in the suite

Store-and-forward

switch always stores the entire frame before forwarding, and checks its CRC and frame length.

What is found on an ARP table?

The layer 2 MAC address that is mapped to the layer 3 IPv4 address

Describe Ethernet.

The most common LAN protocol in the world. It operates layer 1 and 2, but is not required for internet communication.

How are ARP requests sent?

This process sends a layer 2 broadcast to all devices on the Ethernet LAN. The frame contains the IP address of the destination and the broadcast MAC address

Which devices on the local segment will receive an ARP request?

When a network device want to communicate with a device on the same network it will send a broadcast ARP request, meaning every device on the network will receive the request.

How does ARP work?

When a packet is sent to the data link layer to be encapsulated into an Ethernet frame, the device refers to a table in its memory to find the MAC address that is mapped to the IPv4 address. This table is called the ARP table or the ARP cache. The ARP table is stored in the RAM of the device.