Ch. 5: Analyzing Etheret LAN Switching

Question 1

broadcast frame

Answer 1

An Ethernet frame sent to destination address FFFF.FFF F.FFFF, meaning that the frame should be delivered to all hosts on that LAN.

Question 2

known unicast frame

Answer 2

An Ethernet frame whose destination MAC address is listed in a switch’s MAC address table, so the switch will forward the frame out the one port associated with that entry in the MAC address table.

Question 3

Spanning Tree Protocol (STP)

Answer 3

A protocol defined by IEEE standard 802.ID. Allows switches and bridges to create a redundant LAN, with the protocol dynamically causing some ports to block traffic, so that the bridge/switch forwarding logic will not cause frames to loop indefinitely around the LAN.

Question 4

unknown unicast frame

Answer 4

An Ethernet frame whose destination MAC address is not listed in a switch’s MAC address table, so the switch must flood the frame.

Question 5

MAC address table

Answer 5

A table of forwarding information held by a Layer 2 switch, built dynamically by listening to incoming frames and used by the switch to match frames to make decisions about where to forward the frame.

Question 6

forward

Answer 6

To send a frame received in one interface out another interface, toward its ultimate destination.

Question 7

flood/flooding

Answer 7

The result of the LAN switch forwarding process for broadcasts and unknown unicast frames. Switches forward these frames out all interfaces, except the interface in which the frame arrived. Switches also flood multicasts by default, although this behavior can be changed.

Question 8

show mac address-table

Answer 8

Shows all MAC table entries of all typed

Question 9

show mac address-table dynamic

Answer 9

Shows all dynamically learned MAC table entries

Question 10

show mac address-table dynamic vlan (vlan-id)

Answer 10

Shows all dynamically learned MAC table entries in that VLAN

Question 11

show mac address-table dynamic address (mac address)

Answer 11

Shows the dynamically learned MAC table entries with that MAC address

Question 12

show mac address-table dynamic interface (interface-id)

Answer 12

Shows all dynamically learned MAC table entries associated with that interface

Question 13

show mac address-table count

Answer 13

Shows the number of entries in the MAC table and the total number of remaining empty slots in the MAC table

Question 14

show mac address-table aging-time

Answer 14

Shows the global and per-VLAN aging timeout for inactive MAC table entries

Question 15

clear mac address-table dynamic

Answer 15

Empties the MAC table of all dynamic entries

Question 16

show interfaces status

Answer 16

Lists one line per interface on the switch, with basic status and operating information for each

Question 17

clear mac address-table dynamic [vlan vlan-number] [interface interface-id] [address mac-address]

Answer 17

Clears (removes) dynamic MAC table entries: either all (with no parameters), or a subset based on VLAN ID, interface ID, or a specific MAC address