Flashcards in Chapter 6 - Sheet1 Deck (53):
Switches enable ____ duplex between host and switch
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
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
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 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
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
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.
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.
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
Hub, Switch, Router: Which of these three creates multiple collision domains?
Hub, Switch, Router: Which of these three increases bandwidth?
Hub, Switch, Router: Which of these three creates multiple broadcast domains?
LAN, from the perspective of VLANs
A LAN consists of all devices in the same broadcast domain
LAN created to support larger buildings
An IEEE standard mechanism (802.3u) with which two nodes can exchange messages for the
purpose of choosing to use the same Ethernet standards on both ends of the link, ensuring that the
link functions and functions well.
3 terms to describe the role of each switch in a campus LAN
access, distribution, core
Access Switch on a Campus LAN
Connect directly to end users, providing user device access to the LAN.
Distribution Switch on a Campus LAN
Provide a path through which the access switches can forward traffic to each other. Access switches connect to at least on distribution switch.
Core Switch on a Campus LAN
Forward traffic between distribution switches. Example: Campus with multiple buildings, each with several distribution switches, needs core switches to connect it all together.
3 most common types of Ethernet today
10Base-T, 100Base-T, 1000Base-T
Max length of 10Base-T, 100Base-T, 1000Base-T ethernet
What organization defines ethernet cableing standards
What category of cabling does 10Base-T call for
Cat3 or higher (two pair)
What category of cabling does 100Base-T call for
Cat5 or higher (two pair)
What category of cabling does 1000Base-T call for
Cat5e or Cat 6 (four pair)
Max distance for 10Base-T
100 meters (328 ft)
Max distance for 100Base-T
100 meters (328 ft)
Max distance for 1000Base-T
100 meters (328 ft)
Max distance for 1000Base-SX
550 meters (1804.5 ft)
Max distance for 1000Base-LX
550 meters (1804.5 ft)
Max distance for 1000Base-LX Single Mode
5km (3.1 miles)
Media for 1000Base-SX
Media for 1000Base-LX, multimode
Media for 1000Base-LX, singlemode
9 micron single-mode fiber
IEEE rules if autonegotiation fails
Use your slowest supported speed. If speed is 10 or 100, use half-duplex. Otherwise, use full-duplex
Cisco rules if autonegotiation fails
Cisco devices can sense speed used by another node. Speed: Sense the speed. If that fails, use IEEE default. Duplex: Use IEE defaults
When a host's duplex is set to a value different from a connected host or switch .Example: Half duplex on a host, full duplex on a switch. This wil lresult in one client (host) using CSMA/CD and sensing collisions that don't exist. The link will be online, but perform poorly.