No relevant resource is found in the selected language.

This site uses cookies. By continuing to browse the site you are agreeing to our use of cookies. Read our privacy policy>Search

Reminder

To have a better experience, please upgrade your IE browser.

upgrade

Configuration Guide - IP Service

S1720, S2700, S5700, and S6720 V200R012(C00 and C20)

This document describes the configurations of IP Service, including IP address, ARP, DHCP, DHCP policy VLAN, DNS, mDNS gateway, mDNS relay, UDP Helper, IP performance optimization, IPv6, DHCPv6, IPv6 DNS, IPv6 over IPv4 tunnel, and IPv4 over IPv6 tunnel.
Rate and give feedback:
Huawei uses machine translation combined with human proofreading to translate this document to different languages in order to help you better understand the content of this document. Note: Even the most advanced machine translation cannot match the quality of professional translators. Huawei shall not bear any responsibility for translation accuracy and it is recommended that you refer to the English document (a link for which has been provided).
DHCP Client Renewal of Its IP Address Lease

DHCP Client Renewal of Its IP Address Lease

IP addresses that are dynamically allocated by a DHCP server have leases. A DHCP Discover message from a DHCP client can carry an expected lease. When allocating network parameters, the DHCP server compares the expected lease with the specified lease in the address pool and allocates an IP address with the shorter of the two leases to the DHCP client. When the lease expires or the client goes offline, the DHCP server reclaims the IP address, which can then be allocated to other clients. This mechanism improves IP address utilization.

To continue to use this IP address, the DHCP client must renew its IP address lease.

The following describes how a DHCP client renews its IP address lease with and without a DHCP relay agent.

IP Address Lease Renewal Without a DHCP Relay Agent

Figure 3-7 shows how a DHCP client renews its IP address lease.

Figure 3-7  Renewing an IP address lease

  1. When the lease reaches 50% (T1) of its validity period, the DHCP client unicasts a DHCP Request message to the DHCP server to request lease renewal. If the DHCP client receives a DHCP ACK message, the IP address lease is successfully renewed (counted from 0). If the DHCP client receives a DHCP NAK message, the DHCP client must send a DHCP Discover message to apply for a new IP address.
  2. If no response is received from the DHCP server when the lease reaches 87.5% (T2) of its validity period, the DHCP client broadcasts a DHCP Request message to request lease renewal. If the DHCP client receives a DHCP ACK message, the IP address lease is successfully renewed (counted from 0). If the DHCP client receives a DHCP NAK message, the DHCP client must send a DHCP Discover message to apply for a new IP address.
  3. If no response is received when the lease expires, the DHCP client stops using the IP address and sends a DHCP Discover message to apply for a new IP address.

When a DHCP client no longer needs to use the allocated IP address and the lease has not expired, the DHCP client sends a DHCP Release message to the DHCP server to request IP address release. The DHCP server saves the configuration of this DHCP client and records the IP address in the allocated IP address list. The IP address can then be allocated to this DHCP client or other clients.

To request a configuration update, a DHCP client can send a DHCP Inform message to the DHCP server.

IP Address Lease Renewal with DHCP Relay Agents

Figure 3-8 shows how a DHCP client renews its IP address lease with a DHCP relay agent deployed.

Figure 3-8  Renewing the IP address lease when a DHCP relay agent is deployed

  1. When the lease reaches 50% (T1) of its validity period, the DHCP client unicasts a DHCP Request message to the DHCP server to request lease renewal. If the DHCP client receives a DHCP ACK message, the IP address lease is successfully renewed (counted from 0). If the DHCP client receives a DHCP NAK message, the DHCP client must send a DHCP Discover message to apply for a new IP address.
  2. If no response is received from the DHCP server when the lease reaches 87.5% (T2) of its validity period, the DHCP client broadcasts a DHCP Request message to request lease renewal. The DHCP relay agent then unicasts a DHCP Request message to the DHCP server. For details about how the DHCP relay agent processes received messages, see DHCP Server Allocating Network Parameters to New DHCP Clients. If the DHCP client receives a DHCP ACK message, the IP address lease is successfully renewed (counted from 0). If the DHCP client receives a DHCP NAK message, the DHCP client must send a DHCP Discover message to apply for a new IP address.
  3. If no response is received when the lease expires, the DHCP client stops using the IP address and sends a DHCP Discover message to apply for a new IP address.

Translation
Download
Updated: 2018-12-24

Document ID: EDOC1100038342

Views: 84138

Downloads: 281

Average rating:
This Document Applies to these Products
Related Documents
Related Version
Share
Previous Next