Topic 2 - LAN Switching Technologies Flashcards
What address table an switch maintains?
MAC Table
what it is, when an entry ages out and is discarded from the MAC address table?
MAC Aging
Store-and-forward switches
Store the entire frame in internal memory and check the frame for errors before forwarding the frame to its destination.
Cut-through switching
the LAN switch copies into its memory only the destination MAC address, which is located in the first 6 bytes of the frame following the preamble.
The switch looks up the destination MAC address in its switching table, determines the outgoing interface port, and forwards the frame on to its destination through the designated switch port.
Fragment-free switching
- Fragment-free switching can be viewed as a compromise between store-and-forward switching and cut-through switching.
- The reason fragment-free switching stores only the first 64 bytes of the frame is that most network errors and collisions occur during the first 64 bytes of a frame
Frame flooding
- Switches determine which port a frame must be sent out to reach its destination.
- If the address is known, the frame is forwarded only on that port.
- If the layer 2 MAC address is unknown, the frame is flooded to all ports except the one from which it originated.
Auto Negotiation
- Switch and the Pc auto negotiate at what speed the data needs to be transferred.
- should be enabled on only one end of the device
Interpret Ethernet frame format
- Preamble – 7 bytes – used for synchronizing the Layer 2 hardware (indicates that a Ethernet Frame follows)
- Start Frame Delimiter – 1 byte – Indicates that the next byte begins the Destination Mac Field
- Destination Mac Address – 6 bytes
- Source Mac Address – 6 bytes
- Length Or Type
Length – 2 bytes – defines the length of the data
field of the frame
Type – 2 bytes – defines the type of protocol
listed inside the frame - Date and Pad – 46 to 1500 bytes – Hold the PDU/IP packet
- Frame Check Sequence (FCS) – 4 bytes – contains a CRC check of the frame – used to check the frame for errors.
Duplex and Speed?
- Duplex and speed should match on both ends or else you will have problems
- Traffic can still pass with mismatched duplex and speed, but you will experience re transmissions and reduced throughput
What port and protocol does the following use?
1 - SSH
2 - Telent
SSH - TCP & port 22 by default.
Telnet -TCP & port 23 by default.
What is the protocol used on Trunk port?
802.1Q
What is the proprietary trunking protocol?
ISL ( Inter - Switch link )
What is a Native VLAN?
The native VLAN is a way of carrying untagged traffic across one or more switches. which comes in untagged on a trunk port.
What is the default Native VLAN?
VLAN 1
Spanning Tree protocol ( STP)
- STP Monitors the network to find all links, making sure that no loops occurs by shutting down any redundant link
- Adding redundant paths and prevent the loop/broadcast storms, unstable mac address table, duplicate frames
- Not only does spanning-tree blocks redundant paths but also re-opens them in case of a link failure.
- All switches communicate using Bridge Protocol Data Units (BPDU) with each other.