Created by Rick Schoenman
about 2 years ago
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Question | Answer |
Which settings are configured using DHCP? | - IP Address - Subnet mask - DNS servers - Default Gateway |
When is the DHCP client service running on a Windows computer? | When the TCP/IP properties are set to automatically obtain an IP address |
How is the period called during which clients can use a DHCP address? | A lease |
What kind of communication is used to by clients to obtain a DHCP lease? | IP Broadcasts |
What are the 4 steps in obtaining a DHCP lease? | 1. DHCPDISCOVER 2. DHCPOFFER 3. DHCPREQUEST 4. DHCPACK |
Can a DHCP server provide IP configuration on a client on a different network? | Yes, but DHCP relays must be configured. Without relays, this is not possible, because DHCP relies on IP broadcasts, which are not routed by design. |
Describe the DCHPDISCOVER phase of the DHCP process | The client sends a broadcast message to 255.255.255.255 (the current local network broadcast address), containing a DHCPDISCOVERY packet. DHCP servers respond to this message. |
Describe the DHCPOFFER phase of the DHCP process | All DHCP servers which received the DHCPDISCOVER packet, resond with a DHCPOFFER packet, which contains a potential IP address. |
Describe the DHCPREQUEST phase of the DHCP process | The client receives a DHCPOFFER message from 1 or more DHCP servers. It picks the first one it receives. The client responds with a DHCPREQUEST that contains the server identifier of the DHCP server it responds to. This is a broadcast message, therefore informing the other DHCP servers that it doesn't accept their DHCPOFFER. |
Describe the DHCPACK phase of the DHCP proccess | Upon receiving the DHCPREQUEST packet, the DHCP server stores the IP address (which was handed out in the DHCPOFFER phase) in the database. The server sends a DHCPACK message to the client. |
Describe the DHCPNAK message | If a DHCP server was not able to provide the IP address as provided in the DHCPOFFER message, it answers with a DHCPNAK instead of a DHCPACK to the DHCPREQUEST message. |
What happens when the DHCP lease reaches 50% of its lease time? | The client attempts to renew the lease by sending a unicast DHCPREQUEST to the server that originally handed out the lease. If in the meantime the DHCP server was updated with new information, this updated information will be handed to the client. |
What happens when the DHCP lease reaches 87,5% of its lease time? | This occurs when the client can not contact the DHCP server at 50% lease time. The client sends a DHCPREQUEST broadcast (instead of unicast) to all DHCP servers for renewal. |
What are 2 scenarios where the client attempts DHCP renewal as well? | - During startup - When a network change occurs |
In DHCPv6, what is stateful configuration? | This means that the DHCP server assigns an IPv6 address to the client, along with other information. |
In DHCPv6, what is stateless configuration? | This means the router assigns an IPv6 address automatically and the DHCP server only assigns other information. |
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