networking network_error ai_generated true

OSPF：邻居10.0.0.2卡在EXSTART状态

OSPF: Neighbor 10.0.0.2 stuck in EXSTART state

ID: networking/ospf-neighbor-stuck-in-exstart

其他格式: JSON · Markdown 中文 · English
80%修复率
87%置信度
1证据数
2024-01-10首次发现

版本兼容性

版本状态引入弃用备注
Cisco IOS 15.7 active — — —
FRRouting 8.4 active — — —
Quagga 1.2.4 active — — —

根因分析

OSPF邻居无法交换数据库描述（DBD）数据包，原因包括MTU不匹配、接口双工模式不匹配或OSPF网络类型配置错误，导致邻接关系无法从EXSTART阶段继续。

English

OSPF neighbors are unable to exchange Database Description (DBD) packets due to MTU mismatch, interface duplex mismatch, or OSPF network type misconfiguration, preventing the adjacency from progressing beyond the EXSTART phase.

generic

官方文档

https://www.cisco.com/c/en/us/support/docs/ip/open-shortest-path-first-ospf/13684-12.html

解决方案

  1. Verify and set the same MTU on both interfaces: `ip mtu 1500` on both ends, or enable IP fragmentation for OSPF with `ip ospf mtu-ignore`.
  2. Ensure both interfaces have the same OSPF network type: `ip ospf network point-to-point` on both sides (common fix for frame relay or Ethernet).
  3. Check for duplex mismatch: use `show interfaces` to confirm both are full duplex; set with `duplex full` if needed.

无效尝试

常见但无效的做法:

  1. 90% 失败

    This restarts the adjacency but the same issue will reoccur because the root cause (e.g., MTU mismatch) is not addressed.

  2. 70% 失败

    The EXSTART state is not timer-dependent; it is a protocol handshake issue. Changing timers only delays the failure.

  3. 85% 失败

    Router ID does not affect the DBD exchange process; the adjacency will still get stuck in EXSTART.