1.3 routing and switching concepts Flashcards
What is a broadcast domain?
A network segment where all nodes are reachable via broadcasts.
What is a collision domain?
A network segment connected by a shared signaling medium where simultaneous data transmissions collide with one another.
What is important to know about broadcasts when it comes to network devices?
Broadcasts pass through switches and are stopped by a router.
Can two connected devices have different broadcast domains and collision domains?
Can two devices share both?
Yes. If two device are connected to a switch they may share broadcast domains, but not collision domains.
Conversely if two devices are connected to a hub they share both broadcast and collision domains.
What is important to know about collisions when it comes to network devices?
Devices connected through wireless signal, a repeater, or a hub all share a single collision domain.
What do half duplex LANs use to prevent collisions?
CSMA/CD; Carrier-sense multiple access with collision detection.
What does Wi-Fi uses to solve the hidden node problem?
CSMA/CA; Carrier-sense multiple access with collision avoidance.
Explain the difference between simplex and duplex.
Simplex: one node can only transmit, and the other can only receive.
Duplex: bi-directional point-to-point communications between nodes. (transceive)
Explain the difference between half duplex, full duplex, and multiplex.
Half duplex: Devices must stop transmitting in order to receive, or stop receiving in order to transmit.
Full duplex: Devices can communicate with each other simultaneously.
Multiplex: Multiple signals are combined into one complex one, often use to emulate full duplex over a half duplex channel.
Why might tunneling protocols and VPNs cause MTU issues?
IP packets have a supported size 1500 bytes or less as specified by the MTU settings; tunneling requires additional encapsulation which eats up the limited amount of bites and forces fragmentation.
What is requires for two VLANs to communicate?
router/L3 switch
How does a trunk function?
It adds a VLAN header to ethernet frames so that traffic is associated with a specific logical segment.
Define 802.1Q
Standard for striping VLANs across different physical switches through a single interface port, called a trunk port.
What is the difference between a default VLAN and a native VLAN?
Default VLAN: the default VLAN number associated with an interface.
Native VLAN: the VLAN on a switch untagged traffic (such as management frames) is sent to.
Why is STP needed?
Ethernet has no mechanism to determine if traffic has been received before by a device, creating loops.
What is port mirroring on a switch?
Port mirroring makes a copy of frames being sent between two devices and sends that copy to another device not involved in the communication.
Does not interrupt communication, typically used for IDS.
What is a DMZ?
Demilitarized zone, allows access to only specific devices on an internal network from the outside.
What is the MAC address table on a switch?
A cache that associates MAC addresses with a physical interface on a switch.
What is an ARP table?
A cache that associates MAC address with an IP address.
What does an ARP request do?
ARP request are broadcasts sent to discover unknown MAC addresses that are associated with a known IPv4 address.
What has replaced ARP in IPv6?
Neighbor Discovery Protocol
What is the difference between CSMA/CD and CSMA/CA?
CSMA/CD : detects when collisions occur in Ethernet, sends a retransmission request.
CSMA/CA : prevent collisions from occurring to begin with in Wi-Fi communications using a jamming signal.
What is a way to troubleshoot MTU issues or determine best manual MTU setting?
Send packet with don’t fragment bit to receive an ICMP message that says whether or not frame size is support.
What are the reserved VLAN numbers?
0, and 4095.
What are the 5 STP port states?
Disabled - Administrator has completely disabled the port, not participating in STP.
Blocking - Not currently forwarding traffic to prevent a loop.
Listening - Not forwarding, cleaning MAC table and listening for other STP devices.
Learning - Not forwarding and adding to the MAC table.
Forwarding - Forwarding data, fully operational.
What is convergence in STP? How does this differ in RSTP?
All network devices “agree” on what the network topology looks like. Convergence is much faster in RSTP than STP.
What are the 3 interface roles for STP?
Root Port- Best path to the root bridge and the only port on the switch that sends data to/from the root bridge.
Blocking/Non-designated Port- Port is not forwarding traffic to prevent a loop.
Designated Port- Best path to adjacent non-root switches away from the root bridge. Root bridge only has DPs.
What are BPDUs
Bridge Protocol Data Units; frames sent from one switch to another to communicate information about itself, such as its bridge ID, root path costs, and port MAC addresses
Power and wattage for standard 802.3af?
PoE:
350mA
DCw15.4
Power and wattage for 802.3at?
PoE+:
600mA
DCw25.5
What is CoS?
Class of service; layer 2 QoS that modifies Ethernet frame headers for priority, is managed by the 802.1Q trunk/switch.
What is Diffserv?
Differentiated services, layer 3, a form of QoS provided by the router based on the QoS bits in the IPv4 header.
What is the difference between the two forms of QoS?
Diffserv operates on layer 3 by modifying IP packet headers.
CoS operates on layer 2 by modifying Ethernet frame headers.
