Chapter 6 - Sheet1 Flashcards
Switches enable ____ duplex between host and switch
full duples
The role of the ethernet switch
Forward ethernet frames to the right destination MAC address
3 goals of switches
Forward / Filter decisions, MAC Address learning, Loop avoidance
Switch’s MAC Address Table AKA
Switching table, bridging table, content addressable memory (CAM) table
Inactivity Timer
For switch MAC address tables, a timer associated with each entry that counts time upward from
0 and is reset to 0 each time a switch receives a frame with the same MAC address. The entries
with the largest timers can be removed to make space for additional MAC address table entries if needed. Entries will high timers may be removed whether or not it’s needed.
Unonwn Unicast Frames
An Ethernet frame whose destination MAC address is not listed in a switch’s MAC address
table, so the switch must flood the frame.
True/False:: Broadcast Frames are not forwarded by switches
FALSE. They are forwarded by switches
Protocol used to prevent layer 2 loops
Spanning Tree Protocol
STP causes each interface on a swtich to settle into which states?
Either blocking or fowarding
Blocking state of STP
Interface cannot forward or recieve data frames
Forwarding state of STP
Interface c an send and receive data frames.
3 internal processing methods for switches
Store-and-forward processing, cut-through, fragment-free
Store-and-forward processing
One of three internal processing options on some Cisco LAN switches in which the Ethernet
frame must be completely received before the switch can begin forwarding the first bit of the
frame.
Cut-through processing
frame is forwarded as soon as enough of the Ethernet header has been received for the switch to
make a forwarding decision, including forwarding the first bits of the frame before the whole
frame is received. Propagates errors, as bits are sent before FCS arrives
Fragment-free processing
first bits of
the frame can be forwarded before the entire frame is received, but not until the first 64 bytes of
the frame are received, in which case, in a well-designed LAN, collision fragments should not
occur as a result of this forwarding logic
ASIC
Application-specific integrated circuits. Switches make decisions based on ASIC chips (hardware) instead of software, like how bridges operate
Typical internal processing method for a switch
Store and forward. Improved latency from the other two methods is negligible, now that switches have ASIC chips and fasther uplilink connections and connections to hosts.
Features offered by a switch not offered by hubs or bridges
Microsegmentation, providing dedicated bandwidth to each host / multiple concurrent conversations between devices on different ports / ports connected to a singel device support full-duplex, doubling amt of bandwidth / rate adaption - devices can use different ethernet speeds to communicate
If a switch’s address table lists the receiving interface as the interface connected to the destination MAC address, what does it do?
The switch filters the frame – ignores it.
How can a collission still occur with a switch
If the host and switch are configured to half-duplex (instead of full-duplex) and they send and receive at the same time. So unlikely, but possible.
Collission Domain
set of network interface cards (NIC) for which a frame sent by one NIC
could result in a collision with a frame sent by any other NIC in the same collision domain.
Broadcast Domain
set of NICs for which a broadcast frame sent by one NIC is received
by all other NICs in the same broadcast domain
Effect of full-duplex on a switch
Doubling capacity – a 100mbps connection becomes 200mbps.
Hub, Switch, Router: Which of these three allow for greater cabling distances?
Hub, Switch, Router
