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Network+ > Lesson 10: Explaining Network Services > Flashcards

Lesson 10: Explaining Network Services Flashcards

1
Q

What is the first step in a DHCP request?

A

The client broadcasts a DHCPDISCOVER packet to find a DHCP server

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2
Q

What is the second step in a DHCP request?

A

If an IP address is available, the DHCP server responds to the client with a DHCPOFFER packet containing the ip address and other configuration information

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3
Q

What is the third step in a DHCP request?

A

The client can choose to accept the offer using a DHCPREQUEST packet that is broadcast onto the network

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4
Q

What is the fourth step in a DHCP request?

A

If the offer is still available, the server will respond with a DHCPACK packet, the client will broadcast an ARP message to check that the address is unused

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5
Q

Define a DHCP scope?

A

A range of IP addresses and options configured on a DHCP server to be server to clients requesting an IP address

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6
Q

What does is mean that a DHCP server maintains a one-to-one mapping of scopes to subnets?

A

No scope can cover more than one subnet and no subnet can contain more than one scope

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7
Q

What are some DHCP options available to a client?

A
  1. Default Gateway
  2. DNS Server
  3. DNS name
  4. NTP server
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8
Q

How are DHCP options presented to clients?

A

By a tag byte (1-254) in the DHCPOFFER and DHCPACK packets

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9
Q

What is the purpose of a DHCP relay agent/server?

A

Allows a server/router to forward DHCP traffic from one subnet to another

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10
Q

How does a DHCP relay server/agent function?

A

The DHCP relay server/agents intercepts broadcast DHCP frames, applies a unicast address for the appropriate DHCP server and forwards the frames to the the subnet the DHCP server is in

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11
Q

How does the DHCP server function after being forwarded a frame?

A

The DHCP server can identify the original IP subnet from the packet and offers a lease from the appropriate scope

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12
Q

What is the purpose of the IP helper command?

A

Command set in a router OS to support DHCP relay and other broadcast forwarding functionality

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13
Q

What is the command to set up broadcast forwading?

A
  1. int eth1
  2. ip helper-address x.x.x.x
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14
Q

What is a fully qualified domain name (FQDN)?

A

Unique label specified in a DNS hierarchy to identify a particular host within a subdomain within the internetwork

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15
Q

What is a fully qualified domain name (FQDN) made up of?

A

A host name assigned within the AS, and a domain name that is registered

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16
Q

What rules must a FQDN follow?

A
  1. Must be unique
  2. Can’t exceed 253 characters
  3. Letters, digits, and hyphens only
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17
Q

Define DNS

A

A global hierarchy of servers that contain information on domains and hosts in those domains that maps FQDNs to IP addresses

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18
Q

What is the DNS hierarchy consist of?

A
  1. Root (.)
  2. Top level domain (TLD)
  3. Second level domain (SLD)
  4. Sub domain
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19
Q

Define the root domain and its puropose

A

There are 13 root level servers in the world, each containing information about the top level domains

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20
Q

Define the top level domain (TLD) and its purpose

A

TLD’s initial purpose was to help classify websites based on their purposes, ownership, or geographical origin (.com, .org, .edu, .uk, .gov)

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21
Q

Define the second level domain (SLD) and its purpose

A

The official domain name of an entity (google, apple, paymentservicenetwork)

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22
Q

Define the sub domain and its purpose

A

A domain that is apart of a domain, in theory, each tier below the root domain is a sub domain (info.paymentservicenetwork, help.google)

23
Q

Define the DNS resolution process

A

The client application (stub server) checks its local cache for a mapping, if no mapping is found it forwards the query to its local name server, if the local name server can’t resolve the query, its performs a recursive query until an IP addresses is returned

24
Q

What is an iterative query/lookup?

A

A query performed between name servers in different domains that responds with a record from its own data store

25
Q

What is a recursive query/lookup?

A

A query performed by a non-authoritative DNS server that takes on the task of querying other DNS servers until it finds the requested record or reaches a timeout

26
Q

What type of DNS servers perform recursive queries?

A

Local DNS servers listed in a client’s DNS configuration

27
Q

Define a DNS zone file

A

Contains numerous resource records about a DNS zone

28
Q

What are the main records in a DNS zone file?

A
  1. A record
  2. AAAA record
  3. CNAME record
  4. MX record
  5. PTR record
29
Q

Define the Start of Authority (SOA) record

A

Identifies the primary authoritative name server for the zone that maintains a full copy of all records as well as contact information for the zone

30
Q

Define an Name Server (NS) record

A

Identifies secondary authoritative name server for the zone

31
Q

What is an A record?

A

An address record used to resolve a hostname to an IPv4 address

32
Q

What is an AAAA record?

A

An address record used to resolve hostname to an IPv6 address

33
Q

What ports do DNS use?

A

UDP port 53

34
Q

What is a CNAME/alias record?

A

A canonical name (CNAME) record is used to configure an alias for an existing A or AAAA record

35
Q

What is round-robin DNS?

A

A load balancing technique using multiple A records that share the same hostname/domain name but map to different IP addresses within the network

36
Q

What is a Mail Exchange (MX) record?

A

Record used to identify an email server for the domain, which requires there to be an associated A or AAAA record, no CNAME

37
Q

What is a Service (SRV) record?

A

Specifies a host and port for specific services such as voice over IP (VoIP), media servers, and AD servers

38
Q

What are the two types of text (TXT) records?

A
  1. Sender Policy Framework (SPF)
  2. DomainKeys Identified Mail (DKIM)
39
Q

What is a Sender Policy Framework (SPF) record?

A

A TXT record used to list the IP addresses or names of servers that are permitted to send email from a particular domain; used to combat the sending of spam

40
Q

What is a DomainKeys Identified Mail (DKIM) record?

A

A specially formatted DNS TXT record that stores the public key the receiving mail server will use to verify a message’s signature

41
Q

What are the two lookup zones a DNS server may have?

A
  1. Forward lookup zone
  2. Reverse lookup zone
42
Q

What is a forward lookup zone?

A

A zone dedicated to forwarding DNS queries and contains A records, AAAA, CNAME, MX, SPF, DKIM

43
Q

What is a reverse lookup zone?

A

A zone dedicated to reverse DNS queries that resolves IP address to hostname and contains pointer (PTR) records

44
Q

What does a pointer (PTR) record consist of?

A

The zone file has a special name containing the first 3 octets of the domain in reverse order appended to “in-addr.arpa”

45
Q

When is DNS used over TCP port 53?

A

When DNS servers are on a network using IPv6 which requires record transfers over 512 bytes

46
Q

What are the two types of DNS servers?

A
  1. Primary
  2. Secondary
47
Q

What is the function of a primary DNS server?

A

The zone records held on the primary DNS server are editable and replicated to other DNS servers in the namespace

48
Q

What is a secondary DNS sever?

A

The DNS server’s zone records are read only, and the server relies on a zone transfer form a primary DNS server

49
Q

Define DNS caching

A

Data store holding results of recent DNS queries

50
Q

What DNS configuration determines DNS caching?

A

By setting a time to live (TTL) value with the record to define how long a query can be kept in cache; the lower the cache the more frequent the record is updated.

51
Q

What is the proper way to change a DNS record?

A

Reducing the TTL before the change, allowing the change to propagate once its made, and reverting to the original TTL

52
Q

What is the windows cmd to troubleshoot DNS?

A

nslookup

53
Q

What is the linux command to troubleshoot DNS?

A

dig

54
Q

What does ICANN manage?

A

DNS and Generic TLDs

Network+ (19 decks)

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