L28. What information does a host obtain via DHCP and how? Flashcards
What is DHCP?
The Dynamic Host Configuration Protocol (DHCP) is a network management protocol used on IP networks for automatically assigning IP addresses and other communication parameters to devices connected to the network using a client–server architecture.
What are the benefits of DHCP?
DHCP automates the assignment and management of IP addresses and other network configuration details. DHCP ensures that devices can seamlessly join networks and maintain their connectivity with minimal manual intervention.
What information does a host obtain via DHCP?
An IP address, subnet mask, default gateway, DNS server addresses, and lease duration
What is the process of a host obtaining information from DHCP?
The host
1. broadcasts a DHCP Discover message
2. receives a DHCP Offer from available servers
3. sends a DHCP Request to accept an offer
4. receives a DHCP Acknowledge confirming the lease and configuration details
When does a device obtain an IP address?
When it connects to a network
Why does a device need an IP address?
Without an IP address, the device cannot participate in network communication
How does a device obtain an IP address?
It sends out a DHCP Discover message. Upon receiving the DHCP Discover message, available DHCP servers respond with a DHCP Offer message. The host then responds with a DHCP Request message, indicating its acceptance of the offered configuration.
How is the DHCP Discover message sent?
It is broadcast to all devices on the local network to locate any available DHCP servers.
What information does a DHCP Offer message include?
An available IP address and configuration parameters such as the subnet mask, default gateway, DNS server addresses, and lease duration
How does a host select which DHCP Offer to accept?
The host may receive multiple offers if there are several DHCP servers on the network, but it typically selects the first offer it receives.
How do DHCP servers know that an IP address has been assigned to a host?
The host, upon accepting a DHCP offer, broadcasts its DHCP request message to inform all DHCP servers that it has accepted an offer, thus preventing other servers from assigning the same IP address to another device.
What happens after a host accepts a DHCP offer and sends a DHCP request?
The selected DHCP server sends a DHCP Acknowledge message to the host, confirming the lease and providing all the necessary configuration details. The host can now configure its network interface with this information.
What configuration details are provided by DHCP and what are they used for?
- IP address: allows the host to identify itself on the network
- Subnet mask: helps the device understand which addresses are within its local network
- Default gateway: typically the router’s IP address, enables the host to communicate with devices outside its local subnet, such as those on the internet
- DNS server addresses: crucial for resolving domain names to IP addresses, allowing the host to access websites and other network services using human-readable names.
What is a DHCP lease?
An important aspect of DHCP is the lease mechanism, which provides the IP address and configuration details for a specific duration. The lease time is included in the DHCP Acknowledge message, informing the host how long it can use the assigned IP address. To maintain its network configuration, the host must periodically renew the lease.
How is a DHCP lease renewed?
The renewal process starts when half of the lease time has elapsed. At this point, the host sends a DHCP Request directly to the DHCP server that provided the lease, asking to renew it. If the lease is extended, and the host can continue using the IP address without interruption.
