Ethernet Swichting Flashcards
LAN Technologies
- Ethernet (wired)
- Wireless LAN
Ethernet Frame Size
Between 64 bytes up to 1518 bytes (preamble excluded)
Name for Frames under 64 bytes and what happens with these?
- collision fragment or runt frames
- automatically discarded
What happens if a small packet (less than 64 bytes) is encapsulated?
additional bits called a pad are added to increase the size
Frames over 1500 bytes are called
- Jumbo frames
- Baby giant frames
MAC-Address has ___ bits
48 bit
Which two parts of a MAC address exist?
- OUI (Organisationally Unique Identifier) (24 bits)
- Vendor assigned (24 bits)
Source MAC Address is always
Unicast
Multicast MAC addresses start with
01-00-5E
Which protocol makes sure there are no loops?
STP (Spanning Tree Protocol)
What is an Uplink-Port and what is special about it?
- Port which is directed to core of network or Internet
- often higher bandwidth than other ports (or fiber)
An Access Point is like a…
Switch
FCS uses ____ for Error Check
CRC (Cyclic Redundancy Check)
Possible DoS Attack with sending Frames
sending too large Frames
Possible DoS Attack on a Switch
flooding the switch with MAC-Table changes
MAC-Filtering is active, what could you try?
manually edit the MAC address
Where does the Switch store the MAC addresses and their port?
MAC-Table
Other name for MAC-Table
CAM (Content addressable memory)
How does the Switch learn new MAC addresses?
looking at the SRC MAC and see if there were changes or it is unknown
How long does a switch usually store entries in the MAC-Table?
5 minutes
Frame-Forwarding Methods
- Store-and-forward
- Cut-through
Types of Cut-through switching
- Fast-Forwarding (directly forwarded)
- Fragment-free switching (only first 64 bytes are checked with the FCS)
How does store-and-forward switching works?
receives the whole frame and checks for error with FCS
When is a buffer needed?
when the destination port is busy due to congestion it stores the frame.
