DHCP option43 configuration on S series switch

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DHCP Option 43 is defined to indicate vendor-specific information. If an AC and APs are on different network segments, the APs cannot discover the AC through broadcast packets. To address this problem, you can configure Option 43 on the DHCP server to advertise the AC IP address to APs.
The S2720, S2750, S5700LI, S5700S-LI, and S5710LI switches in earlier versions of V200R007 do not support the DHCP Option configuration.
All switches in V200R007 and later versions support the DHCP Option configuration.
When an S series switch except an S1700 switch functions as the DHCP server, configure Option 43 as follows (here, the AC IP address is 192.168.22.1):
- For a global address pool:
[HUAWEI] dhcp enable
[HUAWEI] ip pool huawei
[HUAWEI-ip-pool-huawei] network 192.168.100.0 255.255.255.0
[HUAWEI-ip-pool-huawei] gateway-list 192.168.100.1
[HUAWEI-ip-pool-huawei] option 43 sub-option 3 hex 31302E31302E31302E31 //Alternatively, you can run the option 43 sub-option 3 ascii 192.168.22.1 command.
- For an interface address pool:
[HUAWEI] dhcp enable
[HUAWEI] interface interface vlanif 100 //Enter the view of the interface connected to APs.
[HUAWEI-Vlanif100] ip address 10.10.10.10 24
[HUAWEI-Vlanif100] dhcp select interface
[HUAWEI-Vlanif100] dhcp server 43 sub-option 3 hex 31302E31302E31302E31 //Alternatively, you can run the dhcp server option 43 sub-option 3 ascii 192.168.22.1 command.
Note: If multiple ACs are deployed, separate multiple IP addresses with commas (,) in the Option 43 configuration command. A comma (,) maps 2C in ASCII code. For example, if IP addresses of two ACs are 192.168.22.1 and 192.168.22.2, configure 3139322E3136382E3130302E322C3139322E3136382E3130302E33 or 192.168.22.1,192.168.22.2 in the command.

Other related questions:
DHCP configuration on S series switch does not take effect
DHCP configuration may not take effect on an S series switch due to the following reasons: 1. DHCP server is disabled on the switch. 2. The DHCP address pool is configured incorrectly. 3. No IP network segment is specified on the interface connected to DHCP clients, or the specified IP network segment is on a different network segment from the address pool. 4. If ACL resources are exhausted, the DHCP commands run globally or on an interface will not take effect.

Method to configure DHCP on S series switches
For S series switches excluding the S1700, the switch can both function as the DHCP server to assign IP addresses to clients and function as a DHCP client to dynamically obtain an IP address from the DHCP server. When the DHCP client and DHCP server are located on different network segments, the switch can also function as the DHCP relay agent to assist DHCP server in allocating IP addresses to clients. In addition, the switch can be configured with DHCP snooping to defend against DHCP attacks.

Method to lock a DHCP address on an S series switch
For S series switches excluding the S1700, when the DHCP server is deployed again, you need to migrate the address pool on the DHCP server to another DHCP server on the live network. To retain the addresses that have been assigned to clients from a global address pool, run the lock command to lock the global address pool. After the lock command is run, the specified IP address pool is locked and IP addresses in this address pool cannot be assigned to clients. When new users get online after the address pool is migrated, they apply for IP addresses from a new address pool. The configuration is as follows: [HUAWEI] ip pool global1 [HUAWEI-ip-pool-global1] lock

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