Network Configurations Lesson 001: DHCP Part 2

DORA

Is the four step process that gives DHCP servers the ability of dynamic assignment when a device connects to a network.

What does DORA stand for?

Discover, Offer, Request, and Acknowledge.

What is Discover?

The first step in the four step DORA process.

When does Discover occur?

Whenever a device connects to a network.

What happens when the Discover step occurs?

Sends out a broadcast message to locate the DHCP server.

What is Offer?

The second step in the four step DORA process.

When does Offer occur?

When the DHCP server responds to the client device with an available IP address from its scope of available IP addresses.

What is Request?

The third step in the DORA process.

When does Request occur?

When the client device accepts the offered IP address by requesting to use it.

What is Acknowledge?

The fourth step in the DORA process.

When does Acknowledge occur?

Occurs when the DHCP server confirms the assignment and completes the lease agreement.

What else is provided during the DORA process?

A subnet mask, a default gateway, and the DNS server that the device should be using.

Subnet Mask

Identifies the network and host portions of the IP address that was assigned to the client device.

Default Gateway

The IP address of the router that will allow the client device to access communications with any devices that exist outside of the local area network.

DNS Server

Is used to resolve domain names to their corresponding addresses on behalf of the client device.

What is needed in order for a client device to have proper connection inside and outside a LAN?

An IP address, a subnet mask, a default gateway, and a DNS server’s IP address.

Static Assignment

Involves manually configuring all four network parameters.

What is configured during a static assignment?

The IP address, subnet mask, default gateway, and DNS server.

Where are the parameters of static assignment assigned?

Directly on the client device.

For what devices is static assignment utilized most often?

Printers, servers, and network hardware.

What is the purpose of static assignment for devices that need it?

The need for consistent addresses for reliable operation.

In what environment is static assignment manageable?

In small networks.

In what environment is DHCP reservations more practical?

On larger networks for the devices that need it for reliable functionality and connectivity.

What happens when a device fails to obtain an address from a DHCP server due to a network issue or misconfiguration?

It falls back to its alternate configuration.

What do devices use in an alternate configuration?

APIPA.

What does APIPA stand for?

Automatic Private IP Addressing.

What is the APIPA address range?

169.254.0.0-169.254.255.255.

What is the CIDR notation for the APIPA address range?

169.254.0.0/16.

What does APIPA do?

Allows the device to communicate with others on the same local network.

What is the caveat to the utilization of an APIPA address?

The client device using it will not be able to access external connections.

What is the alternative to an APIPA address?

A fallback static IP.

Why would a network administrator decide to utilize a fallback static IP?

To ensure connectivity for devices that are required to have a connection even if DHCP fails.