# NDP：对fe80::1在eth0上的邻居请求失败，无回复

- **ID:** `networking/ipv6-ndp-failure`
- **领域:** networking
- **类别:** network_error
- **验证级别:** ai_generated
- **修复率:** 80%

## 根因

IPv6邻居发现协议（NDP）发送了邻居请求以解析fe80::1的链路层地址，但未收到邻居公告，表明邻居不可达或未响应。

## 版本兼容性

| 版本 | 状态 | 引入 | 弃用 |
|------|------|------|------|
| Linux kernel 6.1 | active | — | — |
| Cisco IOS XE 17.9 | active | — | — |
| Windows Server 2022 | active | — | — |

## 解决方案

1. ```
   Verify IPv6 connectivity with ping: ping6 -c 3 fe80::1%eth0
   ```
2. ```
   Flush the neighbor cache and retry: ip -6 neigh flush all && ip -6 neigh show
   ```

## 无效尝试

- **** — Disabling IPv6 on the interface (sysctl net.ipv6.conf.eth0.disable_ipv6=1) avoids the issue but loses IPv6 connectivity entirely. (90% 失败率)
- **** — Manually adding a static neighbor entry (ip -6 neigh add fe80::1 lladdr 00:11:22:33:44:55 dev eth0) may fail if the link-layer address is incorrect or the neighbor is genuinely unreachable. (70% 失败率)