1.8 Flashcards
(19 cards)
DNS
translates IP to names
hierarchical
Distributed database, many DNS servers
gTLDs, ccTLDs
FQDN
Fully Qualified Domain Name
katie.east.professormesser.com
Internal vs External DNS
Internal - managed locally, for keeping DNS information private
External - managed by 3rd party, no info by internal devices
Third-party/Cloud DNS
Outsource internal DNS services
additional features-high availability, low latency, scaling options
Resource Reocrds (RR)
text file database of names
A, AAAA
Address records - associate name with ip
A - associate ipv4 with name
AAAA - associate ipv6 with name
CNAME
Canonical Name Record
A name is alias of another canonical name
ftp, www, gopher all translate to mail.mydomain.name
SRV
Service Records
Find a specific service
Where is the domain controller, where is the voip controller
_ladap._tcp.domain.com TTL class SRV priority weight port target (sl.domain.com)
MX
mail exchange
determines the host name for mail server
NS
Name server records
specifies class, server, name
later find A records that translate the name of the NS to ip address
ns1.example.com is NS, A record is ns1=192.xx
PTR
Pointer record
reverse of an A or AAAA record
added to a reverse map zone file
list ip, specify PTR, provide FQDN
TXT
Text Record
useful to 3rd party. might contain SPF protocol (sender policy framework. type of text message that prevents someone from spoofing mail domain
Can add DKIM (domain keys identified mail), digitally sign your outgoing mail. put your public key in the DKIM TXT record
DHCP History
IP addressing used to be manual
October 1993 - BOOTP, didn’t define everything, didn’t know when IP became available
1997 - DHCP
DHCP relay / IP helper
Router configuration if DHCP server on different broadcast domain
takes broadcast normally stopped by router, converts to unicast and sends to DHCP server
IPAM
IP address management plan, track, configure DHCP report on IP usage identify problems and shortages ipv4 and ipv6
Scope
Pool
Scope-ip address range, subnet mask, lease duration
other scope options - DNS, Default gateway, WINS server
Pool-grouping IP addresses , each subnet has it’s own scope
DHCP address allocation
dynamic - big pool, addresses reclaimed after a lease period
automatic - server keeps a list of past assignments, you always get same address
static- manually configured, table of MAC addresses
Lease
administratively configured. if you reboot, you will get same IP if available and lease time reset
T1 timer- 50% of lease time, check in to renew
T2 timer - 87.5% (7/8) of lease time, rebind with any DHCP server if original is down
NTP
synchronizing clocks is critical due to logs, authentication
flexible-you control how clocks are updated
NTP server - respond to time requests from NTP clients, doesn’t modify own time. device can be both
stratum layers-distance away from reference clock. stratum 0 - atomic clock, stratum 1 then stratum 2
