CompTIA Network+ N10-006 - 1.3 Flashcards
DHCP Address Allocation
+ Dynamic allocation
- DHCP server has a big pool of IP addresses to give out.
- Address are reclaimed after a lease period.
+ Automatic allocation
- Similar to dynamic allocation
- DHCP server keeps a list of past assignments
- You’ll always get the same IP address
+ Static allocation
- Administratively configured
+ Table of MAC addresses
- Each MAC address has a matching IP address
+ Other names
- Static HDCP Assignment
- Static DHCP
- Address Reservation
- IP Reservation
DHCP Scopes
+ Grouping of IP addresses
- Each subnet has its own scope
- 192.168.1.0/24
- 192.168.2.0/24
- 192.168.3.0/24
- …
+ A scope is generally a single contiguous pool of IP addresses
- DHCP exceptions can be made inside of the scope.
Scope Properties
+ IP address range
+ Subnet mask
+ Lease durations
+ Other scope options
- DNS server
- Default gateway
- Windows server - configure all scopes subnet on the network.
DHCP leases
+ Leasing your address
- It’s only temporary
- But it can seem permanent
+ Allocation
- Assigned a lease time by the DHCP server
- Administratively configured
+ Reallocation
- Reboot your computer
- Confirms the lease
+ Workstation can also manually release the IP address
- Moving to another subnet
DHCP renewal
+ T1 timer
- Check in with the lending DHCP server to renew the IP address - 50% of the lease time (by default)
+ T2 timer
- If the original DHCP server is down, try rebinding with any DHCP server.
- 87.5% of the lease time (7/8ths)
i.e.
Lease Time: 8 days Renewal Timer (T1): 4 days (50%) Reminding Timer (T2): 7 days (87.5%)
DHCP options
+ A special field in the DHCP message
- Many, many options
+ Options are part of the DHCP RFC
- BOOTP called them “vendor extensions”
+ 256 (254 usable) options
- 0 through 255
- 0 is pad, 255 is end
+ Many common options
- Subnet mask, domain name server, domain name, etc.
+ Options are configured on the DHCP server
- Not all DHCP servers support option configuration
+ Options have been added through the years
- Option 120: Call Server IP address
- option 135: HTTP Proxy for phone-specific applications
Domain Name System
+ Translates human-readable names into computer-readable IP addresses
- You only need to remember www.ProfessorMesser.com, google.com, Netflix.com
+ Hierarchical
- Follow the path
+ Distributed database
- Many DNS servers
- 13 root server clusters
- Hundreds of generic top-level domains (gTLDs) - .com, .org, .net, etc.
- Over 275 country code top-level domains (ccTLDs) - .us, .ca, .uk, etc.
FQDN (Fully Qualified Domain Name)
All the devices below the hierarchy
DNS process
Resolver -> Local Name Server Root Server
Results are now cached
DNS records
+ Resource Records (RR)
- The database records of domain name services
+ Over 30 record types
- IP addresses, certificates, host alias names, etc.
Address records (A) (AAAA)
+ Defines the IP address of a host
- This is most queries
+ A records are for IPv4 addresses
- Modify the A record to change the host name to IP address resolution
+ AAAA (Quad A) records are for IPv6 addresses
- The same DNS server, different records
Www.professormesser.com. IN A 162.159.246.164 ; Professor Messer
^ (an A record)
IN = Internet
Canonical name records (CNAME)
• A name is an alias of another, canonical name
– One physical server, multiple services
; Alias (canonical) names
Gopher IN CNAME mail.mydomain.name.
Ftp. IN CNAME mail.mydomain.name.
Www. IN CNAME mail.mydomain.name.
IN = Internet
Mail exchanger record (MX)
• Determine the host name for the mail server
– This isn’t an IP address; it’s a name
Pointer record (PTR)
• The reverse of an A or AAAA record
– Added to a reverse map zone file
PTR = pointer
Dynamic DNS updating
• Dynamic DNS Update (DDNS)
– Update name server records with a secure, automated process
• DHCP means that address change all the time
–End-stations inform the DNS server of their IP address
• Part of Windows Active Directory
– Domain controllers register in DNS
– Allows other computers in the domain to find the AD servers
