Chapter 7 Flashcards
An Ethernet frame sent to destination address FFFF.FFFF.FFFF, meaning that the frame should be delivered to all hosts on that LAN.
Broadcast frame
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.
Known unicast frame
A protocol that uses a specific algorithm, allowing a switch to dynamically work around loops in a network topology by creating a spanning tree. Switches exchange bridge protocol data unit (BPDU) messages with other switches to detect loops and then remove the loops by blocking selected switch interfaces.
Spanning Tree Protocol (STP)
An Ethernet frame whose destination MAC address is not listed in a switch’s MAC address table, so the switch must flood the frame.
Unknown unicast frame
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.
MAC address table
To send a frame received in one interface out another interface, toward its ultimate destination.
Forward
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.
Flood
What three primary actions do switches perform?
(1) Forwards or filters frames based on destination MAC address
(2) Learning MAC addresses by looking at the source MAC address
(3) Uses Spanning Tree Protocol (STP) to prevent loops
A switching MAC address table is also called a _____ table or a _____ table. It is even called a Content Addressable _____ table.
switching;
bridging
Content Addressable Memory (CAM)
Switches build the address table by listening to incoming frames and examining the _____ MAC address in the frame.
source
If a frame enters the switch and the source MAC address is not in the MAC address table, what does it do?
Creates an entry in the table
What does a switch do when there is no matching entry in the table for the destination MAC address of an incoming frame?
Floods it out all interfaces except incoming one
What is the frame called whose destination address is unknown to the switch?
unknown unicast frame
STP causes each interface on a switch to settle into either a _____ state or a _____ state.
blocking
forwarding
What STP state means that the interface cannot forward or receive data frames?
blocking
What STP state means the the interface can send and receive data packets?
forwarding
What two things does a switch do with a known unicast frame?
Different interface on MAC table forward the frame
Same interface on MAC table filter the frame
How does STP prevent loops?
Blocks certain interfaces from sending or receiving
How does a switch learn MAC addresses?
Builds MAC address table from source addresses of frames received
What does a switch do with an unknown destination unicast?
Forwards frame out all interfaces except receiving interface
What show interfaces command option lists the number of unicast, multicast, and broadcast frames both the in and out direction, and a total byte count for those frames.
counters
Sometimes a network engineer might be troubleshooting while looking at a network topology diagram, and want to look at all the MAC addresses learned off a particular port. IOS supplies that option with what command?
show mac address-table dynamic interface
