2.6 - DHCP Configuration

Question 1

Scope properties

Answer 1

• IP address range
  – And excluded addresses
• Subnet mask
• Lease durations
• Other scope options
  – DNS server
  – Default gateway
  – VOIP servers

Question 2

DHCP pools

Answer 2

• 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

Question 3

DHCP address assignment

Answer 3

• Dynamic assignment
  – DHCP server has a big pool of addresses to give out
  – Addresses are reclaimed after a lease period
• Automatic assignment
  – Similar to dynamic allocation
  – DHCP server keeps a list of past assignments
  – You’ll always get the same IP address

Question 4

DHCP address allocation

Answer 4

• Address reservation
  – Administratively configured
• Table of MAC addresses
  – Each MAC address has a matching IP address
• Other names
  – Static DHCP Assignment, Static DHCP,
  Static Assignment, IP Reservation

Question 5

DHCP leases

Answer 5

• 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

Question 6

DHCP renewal

Answer 6

• 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)

Question 7

The DHCP lease process (graphic)

Answer 7