ARP, MAC & IP
Switches and More
Ethernet Frame
Terms and Concepts 1
Terms and Concepts 2
100
What information is mapped together in the ARP table?
The switch ARP table keeps a mapping of Layer 2 MAC addresses to Layer 3 IP addresses. These mappings can be learned by the switch dynamically through ARP or statically through manual configuration.
100
What does auto-MDIX do?
Auto-MDIX is a feature that is enabled on the latest Cisco switches and that allows the switch to detect and use whatever type of cable is attached to a specific port.
100
What happens to runt frames?
The frame is dropped by the receiving device.
100
What is Unicast
A message that is sent from a single sender to a single recipient.
100
What is multicast
A message that is sent from a single sender to a group of recipients - more than one, but not all
200
When is a MAC address used on a Ethernet network?
A MAC address is only useful on the local Ethernet network. When data is destined for a remote network of any type, the data is sent to the MAC of the default gateway device, the Layer 3 device (Router) that routes the local network to remote networks.
200
How does a switch build its MAC address table?
A switch builds a 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.
200
What is the 1 main characteristic of a MAC address?
It is unique. No other devices on the planet can have the same MAC address.
200
What does ARP do?
(Address Resolution Protocol)
The process that is used to find a Layer 2 address (MAC) when a Layer 3 address (IP) is known
200
What is cut-through switching
A switching method that begins the forwarding process as soon as enough information has been received to make a forwarding decision
300
If a device sends out a ARP request what is the process that happens next...
A Broadcast (ff:ff:ff:ff:ff:ff) is sent out to every device on the local network. Every device replies back with their IP and MAC.
300
What switching method uses the cyclic redundancy check (CRC) value in a frame to determine if the frame has been modified during transit?
What is store-and-forward.
300
Where is the logical link control implemented.
Logical link control is implemented in software.
300
What is fast-forward switching
A cut-through switching method that begins to forward data as soon as the destination address has been received
300
What is broadcast
A message that is sent from a single sender to all recipients
400
What are the negative issues with ARP requests?
One of the negative issues with ARP requests is that they are sent as a broadcast. This means all devices on the local link must receive and process the request.
On large networks with low bandwidth, multiple ARP broadcasts could cause data communication delays.
Network attackers could manipulate MAC address and IP address mappings in ARP messages with the intent of intercepting network traffic.
400
What are the characteristics of port-based memory buffering?
Buffering is a technique used by Ethernet switches to store frames until they can be transmitted. With port-based buffering, frames are stored in queues that are linked to specific incoming and outgoing ports.
400
A device uses ARP to find the local address of a device on it's network using this...
Broadcast MAC address of FFFF.FFFF.FFFF
400
What is the Organizationally Unique Identifier
OUI
A three-byte code that is assigned by IEEE to identify the vendor of a NIC.
The first 3 bytes are used for vendor identification and the last 3 bytes must be assigned a unique value within the same OUI.
400
What is fragment-free switching
A cut-through switching method that begins to forward data after receipt of the first 64 bytes of a frame
500
What is a ARP spoofing attack?
In an ARP spoofing attack, a malicious host intercepts ARP requests and replies to them so that network hosts will map an IP address to the MAC address of the malicious host.
500
What are the characteristics of the Cut-Through forwarding method?
- A cut-through switch can forward frames before receiving the destination address field.
- Presenting less latency than a store-and-forward switch.
- Because the frame can begin to be forwarded before it is completely received, the switch may transmit a corrupt or runt frame.
500
How does the Data link layer communicate with the upper layers of the protocol suite?
The data link layer communicates uses the LLC with the upper layers of the protocol suite.
500
What is auto-MDIX and what does it do?
A feature that detects the type of cable, and configures the interfaces to allow the connection
500
What is a logical address
A Layer 3 address (IP) that identifies both the network and the specific host on that network
600
If PC B sends out a ARP Request who will reply?
PC A & PC C will respond. PC D is on a different Broadcast domain.
600
What are the characteristics of Store-and-Forward forwarding method?
- A store-and-forward switch always stores the entire frame before forwarding.
- It checks its CRC and frame length to make sure no bits have been changed.
600
What are the min and maximum sizes a frame can be.
The minimum Ethernet frame known as a Runt is 64 bytes.
The maximum Ethernet frame known as a Jumbo is 1518 bytes.
600
What is a physical address and what does it do?
A Layer 2 address (MAC) that allows NICs to communicate with each other.
600
What is store-and-forward switching
A switching method that receives the entire frame before forwarding