Two dhcp servers load balance or HSB

Created: May 27, 2019 12:35:34Latest reply: May 27, 2019 14:27:39 60 2 0 0
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We have two dhcp servers, and S5720LI act as the access switch.

what we want to know is how to configure the s5720 to send the dhcp request packets to the 2nd dhcp server only if the 1st dhcp server turns down, or send the request packets to the 2nd dhcp server only if the addres pool on the 1st dhcp server used up. can we do that?

appreciate for any suggestions.

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Featured Answers
Admin Created May 27, 2019 12:37:24 Helpful(0) Helpful(0)

@user_3357111 hi!

No, you can configure the switch to send the DHCP request packets in hot standby.

Each time when a DHCP relay agent receives a DHCP Request packet, it adjusts the order of the DHCP servers to which the request packet is sent to achieve load balancing among all DHCP servers.
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All Answers
chenhui Admin Created May 27, 2019 12:37:24 Helpful(0) Helpful(0)

@user_3357111 hi!

No, you can configure the switch to send the DHCP request packets in hot standby.

Each time when a DHCP relay agent receives a DHCP Request packet, it adjusts the order of the DHCP servers to which the request packet is sent to achieve load balancing among all DHCP servers.
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Sergio93 Created May 27, 2019 14:27:39 Helpful(0) Helpful(0)

Hello,

If the DHCP servers are placed in a Layer 2 network, the DHCP Discover as it's a broadcast packet will reach both of them and the client will receive the Offer from one of them(considering that one is Down).
Now, if the servers are placed in a Layer 3 network and you need to configure DHCP Relay, you can have a look at this command: 
https://support.huawei.com/hedex/hdx.do?docid=EDOC1000177841&id=dhcp_relay_server-ip_1&text=dhcp%252520relay%252520server-ip&lang=en 

If multiple DHCP server addresses are configured on an interface, multiple DHCP servers respond with DHCP Offer messages to the DHCP client. However, the DHCP client uses the first received DHCP Offer message. As a result, IP addresses in the IP address pool on the first DHCP server are insufficient, but available IP addresses in the IP address pools on the other DHCP servers are not allocated. To make each DHCP server allocate the same number of IP addresses, a DHCP relay agent changes the forwarding order each time it forwards a DHCP Discover message, so that load balancing is implemented among DHCP servers. A DHCP relay agent forwards a DHCP Discover message as follows:
  • The DHCP relay agent forwards the message to all DHCP servers by default, and changes the forwarding order each time it forwards a DHCP Discover message.
  • You can configure the ip relay address cycle command to reduce the number of packets received by a DHCP server and lessen the load of a DHCP server. After this command is configured, the DHCP relay agent forwards a received DHCP Discover message to one DHCP server at a time, and forwards the DHCP Discover message to a different DHCP server each time it receives the message.
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