# DHCP DECLINE：地址192.168.1.100已在网络上使用

- **ID:** `networking/dhcp-address-already-used`
- **领域:** networking
- **类别:** network_error
- **验证级别:** ai_generated
- **修复率:** 88%

## 根因

DHCP客户端通过ARP探测发现提供的IP地址已被其他主机使用，因此向服务器发送了DHCPDECLINE。

## 版本兼容性

| 版本 | 状态 | 引入 | 弃用 |
|------|------|------|------|
| ISC DHCP 4.4.3 | active | — | — |
| dnsmasq 2.89 | active | — | — |
| systemd-networkd 250 | active | — | — |

## 解决方案

1. ```
   Identify and remove the conflicting static IP host, then release the address: arp -d 192.168.1.100; dhclient -r eth0; dhclient eth0
   ```
2. ```
   Exclude the conflicting address from the DHCP pool in the server config (e.g., in dhcpd.conf: deny 192.168.1.100;)
   ```

## 无效尝试

- **** — The conflict is due to a static IP assignment on another host; restarting the server does not resolve the conflicting address. (90% 失败率)
- **** — Lease time does not affect address conflicts; the client's ARP probe detects the conflict regardless of lease duration. (95% 失败率)