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DHCP报文问题

2023-10-20提问

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珍珠奶茶

珍珠奶茶四段

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问题描述：

以下是个人排查问题时遇到的情况，小萌新一枚，也许问题比较简单，但是现场没反应过来，请各位前辈根据，所描述现象看看个人的分析是否合理

局部组网环境：

PoE直连无线AP设备（PoE未开启边缘端口）

问题描述：

1、AP未获取IP地址

2、AP上进行debugging dhcp client packet,发现AP发出多个discover报文，但只收到一个Offer报文和ACK报文，且Offer和ACK报文中的Client hardware address字段不一致（debugging已在下面给出------组网及组网描述）

疑惑点：

交换机根据源MAC 进行端口和MAC地址的绑定，但是PoE交换机和单台AP直连（中间未连接其他设备），AP未上线，所以不可能有客户端接入，Offer报文是单播报文，PoE根据MAC地址表项转发单播报文，为什么AP收到了 Offer报文甚至还有ACK报文呢？

个人分析：

1、该PoE上交换机下还连接着其他AP，均未上线,PoE连接AP端口未设置成边缘端口

2、未上线AP到达重启时间重启，PoE端口UP，触发STP拓扑变更，导致发出TC报文

3、TC报文触发PoE刷新MAC地址表项，导致单播的DHCP Offer和ACK被泛洪至AP以至于被AP debugging到

组网及组网描述：

Sep 20 00:08:30:779 2022 H3C DHCPC/7/PACKET: To 255.255.255.255 port 67, interface Vlan-interface1 Message type: REQUEST (1) Hardware type: 1, Hardware address length: 6 Hops: 0, Transaction ID: 1692080497 Seconds: 0, Broadcast flag: 1 Client IP address: 0.0.0.0 Your IP address: 0.0.0.0 Server IP address: 0.0.0.0 Relay agent IP address: 0.0.0.0 Client hardware address: 8c94-6abd-cf20 Server host name: not configured Boot file name: not configured DHCP message type: DHCPDISCOVER (1)

*Sep 20 00:08:44:779 2022 H3C DHCPC/7/PACKET: To 255.255.255.255 port 67, interface Vlan-interface1 Message type: REQUEST (1) Hardware type: 1, Hardware address length: 6 Hops: 0, Transaction ID: 1692080497 Seconds: 0, Broadcast flag: 1 Client IP address: 0.0.0.0 Your IP address: 0.0.0.0 Server IP address: 0.0.0.0 Relay agent IP address: 0.0.0.0 Client hardware address: 8c94-6abd-cf20 Server host name: not configured Boot file name: not configured DHCP message type: DHCPDISCOVER (1)

*Sep 20 00:09:41:213 2022 H3C DHCPC/7/PACKET: From 10.17.64.1 port 67, interface Vlan-interface1 Message type: REPLY (2) Hardware type: 1, Hardware address length: 6 Hops: 0, Transaction ID: 406600114 Seconds: 0, Broadcast flag: 1 Client IP address: 0.0.0.0 Your IP address: 10.17.67.246 Server IP address: 0.0.0.0 Relay agent IP address: 0.0.0.0 Client hardware address: 30c6-d755-3880 Server host name: not configured Boot file name: not configured DHCP message type: DHCPOFFER (2)

*Sep 20 00:09:41:235 2022 H3C DHCPC/7/PACKET: From 10.17.64.1 port 67, interface Vlan-interface1 Message type: REPLY (2) Hardware type: 1, Hardware address length: 6 Hops: 0, Transaction ID: 406600114 Seconds: 0, Broadcast flag: 1 Client IP address: 0.0.0.0 Your IP address: 10.17.67.246 Server IP address: 0.0.0.0 Relay agent IP address: 0.0.0.0 Client hardware address: 30c6-d755-3880 Server host name: not configured Boot file name: not configured DHCP message type: DHCPACK (5)