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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.
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Master/Backup DHCP Server Application

Master/Backup DHCP Server Application

As shown in Figure 3-13, an enterprise can deploy a master and backup DHCP server to improve network reliability. If the master DHCP server is faulty, the backup DHCP server dynamically allocates IP addresses to hosts, ensuring uninterrupted services on the hosts.

Figure 3-13  Master and backup DHCP server deployment

VRRP is configured on Switch_1 and Switch_2 that both function as DHCP servers with Switch_1 as the master device and Switch_2 as the backup device. Normally, Switch_1 dynamically allocates IP addresses to clients. If Switch_1 fails, a master/backup VRRP switchover is triggered, and Switch_2 becomes the master device. Switch_2 then dynamically allocates IP addresses to clients.

The master and backup devices in a VRRP group cannot back up data in real time. To prevent IP address conflicts, different address pool ranges must be configured on the master and backup devices. After a master/backup switchover, Switch_2 allocates network parameters including IP addresses to new DHCP clients. If a client that obtained an IP address from Switch_1 sends a DHCP Request message to renew its IP address lease, Switch_2 finds no information about the IP address. Switch_2 then sends a DHCP NAK message to ask the client to apply for a new IP address.

When the original master device (Switch_1) recovers, service traffic can be switched back to the master device or retained on the backup device, depending on the configuration.

Updated: 2018-12-24

Document ID: EDOC1100038342

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