2.5 - Assigning IP Addresses Flashcards
1
Q
DHCP (origins and purpose)
A
- IPv4 address configuration used to be manual
– IP address, subnet mask, gateway,
DNS servers, NTP servers, etc. - October 1993 - The bootstrap protocol (BOOTP)
- BOOTP didn’t automatically define everything
– Some manual configurations were still required
– BOOTP also didn’t know when an
IP address might be available again - Dynamic Host Configuration Protocol (DHCP)
– Initially released in 1997,
updated through the years
– Provides automatic address / IP configuration
for almost all devices
2
Q
The DHCP Process (DORA)
A
-
Step 1: Discover - Client to DHCP Server
– Find all of the available DHCP Servers -
Step 2: Offer - DHCP Server to client
– Send some IP address options to the client -
Step 3: Request - Client to DHCP Server
– Client chooses an offer and makes a formal request -
Step 4: Acknowledgment - DHCP Server to client
– DHCP server sends an acknowledgment to the client
3
Q
Turning dynamic into static
A
- DHCP assigns an IP address from the first available from a
large pool of addresses
– Your IP address will occasionally change - You may not want your IP address to change
– Server, printer, or personal preference - Disable DHCP on the device
– Configure the IP address information manually
– Requires additional administration - Better: Configure an IP reservation on the DHCP server
– Associate a specific MAC address with an IP address
4
Q
Avoid manual configurations
A
- No DHCP server reservation
– You configure the IP address manually - Difficult to change later - You must visit the device again
- A DHCP reservation is preferable
– Change the IP address from the DHCP server
5
Q
Automatic Private IP Addressing (APIPA)
A
- A link-local address - No forwarding by routers
- IETF has reserved 169.254.0.0 through 169.254.255.255
– First and last 256 addresses are reserved
– Functional block of169.254.1.0 through 169.254.254.255 - Automatically assigned
– Uses ARP to confirm the address isn’t currently in use
