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Autumn 2024 > Computer Networks and Internets > Flashcards

Computer Networks and Internets Flashcards

1
Q

Name the switch LEDs

A

SYST, RPS, STAT, DUPLX, SPEED and PoE

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2
Q

What is the 5 step boot sequence that a cisco switch runs through?

A

POST (self test)
Boot Loader
Low level CPU initialisation
Flash file system initialisation
IOS

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3
Q

What does the boot loader do?

A

Provide access to the switch if the OS cannot be used

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4
Q

What do you do to prepare a switch for remote management access?

A

It needs to be configured with an IP address and a subnet mask, and default gateway

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5
Q

What does full duplex communication do?

A

Increases bandwidth by allowing both ends of a connection to simultaneously receive and transmit data

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6
Q

What to do if the speed and duplex settings of a device are unknown or may be changed?

A

Use autonegotiation

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7
Q

What does auto-MDIX do?

A

It automatically detects the required cable type for the connection

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8
Q

What ports do Telnet and SSH use?

A

Telnet - 23
SSH - 22

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9
Q

What is the difference between Telnet and SSH?

A

Telnet uses plaintext transmission of data and authentication information, whereas SSH provides strong encryption for login authentication and data

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10
Q

What are the steps to configure ssh?

A

Verify SSH support, configure IP domain, generate RSA keys, configure use authentication, vty lines and SSH version 2

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11
Q

What is the IPv4 loopback interface?

A

It is a logical interface that is internal to a router that is useful for testing and debugging

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12
Q

What are the filter show command options?

A

include, exclude, begin, section

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13
Q

How many lines does command history capture?

A

10 lines

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14
Q

How are frames forwarded in a switching network?

A

The switch examines the destination address of the frame, looks for a matching port in its MAC table and sends it through

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15
Q

Compare a collision domain to a broadcast domain

A

Network segments that share the same bandwidth are called collision domains
A collection of interconnected switches form a broadcast domain
Switches extend broadcast domains but eliminate collision domains
Broadcast domains can be broken up by a router

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16
Q

What are the characteristics to alleviate network congestion?

A

High port density, fast port speeds, large frame buffer, fast internal switching

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17
Q

What are the two methods of switching?

A

Cut through switching - as soon as the frame is received. Can send error frames

Store-and-forward - after the entire frame is received, performs error checks to ensure valid frames are sent

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18
Q

Why are VLANs used in a switched network?

A

To allow logical broadcast domains within a network and easier management, higher security and better performance

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19
Q

What is a trunk?

A

A point to point link between switches that carries traffic for all VLANs

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20
Q

What is trunk negotiation managed by?

A

DTP or Dynamic Trunking Protocol

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21
Q

What are the types of VLANs?

A

Native, Management, Data, Default, Voice

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22
Q

What is inter-vlan routing?

A

The process of forwarding network traffic from one VLAN to another - legacy, router-on-a-stick and layer 3 switches using SVIs

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23
Q

How does router-on-a-stick VLAN routing work?

A

Subinterfaces are configured on the router interface for each VLAN, with an IP Address on a unique subnet

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24
Q

What are the steps to configure a switch with VLANs and Trunking?

A

create VLANs, create SVI VLAN interfaces, configure access ports and enable IP routing

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25
Q

What is a common problem of a redundant Layer 2 switched network?

A

The possibility of physical and logical layer 2 loops, resulting in MAC instability and high CPU utilization

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26
Q

What is an STP

A

A loop prevention protocol that allows redundancy while keeping a loop free topology

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27
Q

How does STP work?

A

STP uses STAlgorithm to find the root bridge, associated root ports and designated ports, and block alternative ports to create the shortest path in the switched network

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28
Q

How is the root bridge determined with multiple candidates?

A

Lowest sender BID, port priority and port id

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29
Q

What are the port states?

A

Blocking, listening, learning, forwarding, disabled

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30
Q

What is RSTP?

A

An evolution of STP that provides faster convergence, with port states learning, forwarding, discarding

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31
Q

What is PVST+

A

Cisco enhancement of STP that provides seperate spanning tree instances for each VLAN. Supports Portfast, root guard, bpdu guard etc

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32
Q

What does PortFast do?

A

The port transitions from blocking to forwarding bypassing the listening and learning states. This is used on access ports to access the network immediately

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33
Q

What is etherchannel

A

A link aggregation technology that allows redundant links that won’t be blocked by STP. Groups multiple links into one logical link

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34
Q

What does EtherChannel provide?

A

Load balancing, increased bandwidth, redundancy

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35
Q

What is the resulting interface called when an EtherChannel is created?

A

Port Channel

36
Q

How can Etherchannels be formed, and what are the modes of the options?

A

PAgP - auto, on, desirable
LACP - on, active, passive

37
Q

What are the rules for Etherchannel?

A

All interfaces must support EtherChannel
All interfaces must operate in the same duplex and speed
All interfaces must be assigned to the same VLAN or be a trunk
All interfaces allow the same VLANs

38
Q

What does a DHCPv4 server do?

A

Dynamically leases an IP address to a client from a pool of addresses

39
Q

Describe the DHCPv4 lease process

A

DHCPDISCOVER
DHCPOFFER
DHCPREQUEST
DHCPACK

40
Q

Describe the DHCP renewal process

A

DHCPREQUEST
DHCPACK

41
Q

Describe the ICMPv6 RA messages

A

A flag – AddressAutoconfiguration flag. Use SLAAC to create an IPv6 GUA.
* O flag – Other Configuration flag. Get Other information from a stateless DHCPv6 server.
* M flag – This is the ManagedAddress Configuration flag. Use a stateful DHCPv6 server to obtain an IPv6 GUA.

42
Q

What process is used to ensure the IPv6 GUA is unique

A

DAD or Duplicate Address Detection - sends neighbour solicitation messages

43
Q

What ports do DHCPv6 messages use?

A

Client to server - UDP 547
Server to client - UDP 546

44
Q

What does stateless DHCPv6 inform?

A

To use the RA message for addressing but the server for other information

45
Q

What does stateful DHCPv6 inform?

A

To obtain all information from the server, but the default gateway from the RA message

46
Q

How can a cisco IOS router be configured to provide DHCPv6 services?

A

server, client or relay agent

47
Q

What is the purpose of FHRP or First Hop Redundancy Protocol?

A

FHRP allows alternate default gateways in networks where two or more routers are connected to the same VLAN

48
Q

Describe a way to prevent single points of failure

A

Implement a virtual router, where multiple routers work together to function as one

49
Q

What happens in FHRP when an active router fails?

A

The standby router stops seeing hello messages, assumes the role of the forwarding router

50
Q

What is HSRP and how does it work

A

Cisco proprietary FHRP that selects active and standby devices. The router with the highest HSRP priority becomes the active router

51
Q

What attacks are endpoints vulnerable to and what do they use as security?

A

DDoS, malware, and used antivirus and firewalls. They are best protected by NAC, AMP, Email security appliance and web security appliance

52
Q

What controls access to a network?

A

AAA authentication, authorisation and accounting

53
Q

What is the IEEE 802.1X

A

Port based access control and authorisation protocol

54
Q

Name the layer 2 security solutions

A

Port security, dhcp snooping, DAI and IPSG

55
Q

What do MAC Address flooding attacks do?

A

bombard the switch with fake source MAC addresses until the switch MAC address table is full.

56
Q

What does a VLAN hopping attack do?

A

Enables traffic from one VLAN to be seen by another

57
Q

What does a VLAN double tagging attack do?

A

Allows traffic to have multiple tags directing it to different VLANs, unidirectional.

58
Q

How can VLAN tagging and hopping be prevented?

A

Disable trunking on all access ports
Disable auto trunking on trunk links
Only use native vlan for trunk links
Disable DTP negotiations, unused ports

59
Q

What are the two DHCP attacks and how are they prevented?

A

DHCP starvation and spoofing - can be prevented with DHCP snooping

60
Q

What is ARP attack and how is it mitigated?

A

A fake MAC is sent to the switch, which accordingly updates its MAC table, then unsolicited ARP replies are sent to hosts on the network.
It is mitigated by implementing DAI

61
Q

What is an Address spoofing attack and how is it mitigated?

A

A hacker hijacks an IP or MAC address. Can be mitigated by implementing IPSG

62
Q

What is an STP attack and how is it mitigated?

A

Threat actor acts as a fake root bridge and intercepts all traffic. This is mitigated with BPDU Guard

63
Q

What does DHCP Snooping do?

A

It determines if DHCP messages are from a legitimate source

64
Q

What does DAI do?

A

Dynamic ARP Inspection requires DHCP snooping and verifies ARP traffic

65
Q

What are the four types of Wireless Lan?

A

WPAN, WLAN, WMAN and WWAN

66
Q

What bands do WLAN networks operate in?

A

2.4 and 5 GHz

67
Q

What is CAPWAP?

A

IEEE standard protocol that enables a WLC to control multiple APs and WLANs

68
Q

Which standards operate in the 2.4 to 2.5 GHz spectrum?

A

b/g/n

69
Q

What are the two security features available on routers and APs?

A

SSID cloaking and MAC address filtering

70
Q

What are the four key authentication techniques

A

WPA, WEP, WPA2, WPA 3

71
Q

How does a router convert private IPv4 addresses to internet routable addresses?

A

Network Address Translation

72
Q

What does network QoS do?

A

Prioritises voice and video traffic types

73
Q

How do routers learn about a network?

A

Static routes and Dynamic routing protocols

74
Q

What are the ways a router can deal with a packet?

A

It can forward it on a directly connected network, to a next hop router, or it can drop it

75
Q

What are the three packet forwarding mechanisms?

A

process switching, fast switching, and CEF

76
Q

What is the difference between static and dynamic routing

A

Static routes are manually configured and define an explicit path between two networking devices.

Dynamic routing protocols can discover a network, maintain routing tables, select a best path, and automatically discover a new best path if the topology changes.

77
Q

What does the default route do?

A

It specifies the next hop router to use when the routing table does not have a specific route

78
Q

What does Cisco use to determine the route in an IP routing table?

A

AD or Administrative Distance. The lower the AD, the more trustworthy the route

79
Q

What is an IGP

A

Routing protocol that exchanges information within a routing domain administered by a single organisation

80
Q

What is an EGP

A

EGP or BGP is a routing protocol that exchanges information between different organisations, and can route packages over the internet

81
Q

How is the best path selected by a routing protocol?

A

By the lowest metric of the route

82
Q

What are the types of static routes?

A

standard, default, floating, summary

83
Q

How can the next hop be identified with a static route?

A

By the IP address, exit interface or both - types: next hop, directly connected and fully specified

84
Q

What is a default route

A

A static route that matches all packages

85
Q

What are floating static routes?

A

Static routes designed to provide a backup for default or static routes, set to a higher administrative distance of 1

86
Q

How does a router process packets when a static route is configured?

A

When a packet arrives on a router interface, it is decapsulated. If the destination IP matches a static route entry, the next hop is identified and forwarded to. If not, the router uses the default static route or drops the packet.

Autumn 2024 (3 decks)

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