When does the DHCP server start to ping a DHCP client

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Starting from V100R006C00, upon receiving the Discover message, an S series switch starts to ping the IP addresses that the DHCP server will assign to a client. For details, see the dhcp server ping command.

Other related questions:
DHCP client cannot obtain a correct IP address
The request packets (DHCP discover) are broadcast by the DHCP clients. If multiple DHCP servers are located on the same subnet (for example, bogus DHCP server), the clients may obtain IP addresses from a bogus DHCP server. To address this problem, configure DHCP snooping. Then clients can receive DHCP packets from only the trusted DHCP server. Perform the following configuration: [Huawei] dhcp enable [Huawei] dhcp snooping enable [Huawei] interface gigabitethernet 1/0/1 //Enter the view of the interface connected to the DHCP client. [Huawei-GigabitEthernet1/0/1] dhcp snooping enable [Huawei-GigabitEthernet1/0/1] quit [Huawei] interface gigabitethernet 1/0/2 [Huawei-GigabitEthernet1/0/2] dhcp snooping trusted //Configure the interface of the DHCP server as the trusted interface. [Huawei-GigabitEthernet1/0/2] quit Note: - When you configure DHCP snooping on a Layer 2 access device, steps 1, 2, and 3 are mandatory and must be performed in the following sequence. - When you configure DHCP snooping on a DHCP relay agent, only steps 1 and 2 are required.

How does an AR used as the DHCP server allocate IP addresses to many DHCP clients
When an AR functions as a DHCP server, you can enlarge the address pool range and shorten the lease of IP addresses to allow DHCP clients to quickly connect to and disconnect from the network.

Method used to configure DHCP relay on the AR
When the DHCP server and DHCP clients are on different network segments, the DHCP relay agent can be configured so that the DHCP server can assign IP addresses to the DHCP clients. Procedure: 1. Configure the router # sysname Router # dhcp enable //Enable the DHCP function. # ip pool ip-pool1 gateway-list 10.10.1.1 //Set the gateway IP address. network 10.10.1.0 mask 255.255.255.128 //Specify the range of IP addresses that can be dynamically allocated in the global address pool. excluded-ip-address 10.10.1.2 //Set the IP address 10.10.1.2 that is not assigned automatically in the address pool. excluded-ip-address 10.10.1.4 //Set the IP address 10.10.1.4 that is not assigned automatically in the address pool. dns-list 10.10.1.2 //Configure the IP address of the DNS server for the DHCP client. nbns-list 10.10.1.4 //Configure the IP address of the NetBIOS server for the DHCP client. lease day 10 hour 12 minute 0 //Set the IP address lease to 10 days and 12 hours. domain-name huawei.com //Set the domain name to huawei.com. static-bind ip-address 10.10.1.5 mac-address fc12-2567-ce34 //Assign a fixed IP address to the PC_AD. # ip pool ip-pool2 gateway-list 10.10.1.129 //Set the gateway IP address. network 10.10.1.128 mask 255.255.255.128 //Specify the range of IP addresses that can be dynamically allocated in the global address pool. dns-list 10.10.1.2 //Configure the IP address of the DNS server for the DHCP client. lease day 5 hour 0 minute 0 //Set the IP address lease to 5 days. domain-name huawei.com //Set the domain name to huawei.com. # interface GigabitEthernet0/0/0 ip address 10.10.1.1 255.255.255.128 dhcp select global //Configure the global address pool mode. # interface GigabitEthernet0/0/1 ip address 10.10.1.129 255.255.255.128 dhcp select global //Configure the global address pool mode. 2. Verify the configuration. Run the display ip pool command on the router to check the IP address pool configuration.

Configure DHCP relay on S series switch
For S series switches (except S1700 switches), when the DHCP server and clients are on different network segments, you can configure a DHCP relay agent to help the DHCP server allocate network parameters to DHCP clients. For S series switches, the DHCP relay agent configuration is the same on all switch models in all versions. For details, see "Example for Configuring the Device as a DHCP Relay (on the Same Network)" and "Example for Configuring the Device as a DHCP Relay (Across a GRE Tunnel)" in Typical Configuration Examples.

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