某局点S7503X keepalive 反复up/down

设备keepalive状态震荡

1、现网环境，终端取不到地址，spine起了dhcp relay，leaf起了dncp snooping，排查发现spine存在DHCP超限丢包记录，同时leaf存在keepalive 反复up/down记录，通过删除dhcp snooping trust后重下恢复。

2、dhcp报文的源终端只在接入下通过vlan 4094接入，debug一直有nak报文。

Message type: REQUEST (1)

    Hardware type: 1, Hardware address length: 6

    Hops: 0, Transaction ID: 2273587435

    Seconds: 0, Broadcast flag: 0

    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: c465-1690-2cb3

    Server host name: not configured

    Boot file name: not configured

    DHCP message type: DHCPREQUEST (3)

*Jul 10 22:28:12:146 2023 BJ-CD-5-leaf-BGW-2 DHCPS/7/EVENT: -MDC=1; Receive a DHCPREQUEST message for 172.16.212.8 from Vsi-interface4094; The server identifier is (none).

*Jul 10 22:28:12:146 2023 BJ-CD-5-leaf-BGW-2 DHCPS/7/PACKET: -MDC=1; To 255.255.255.255 port 68, interface Vsi-interface4094

    Message type: REPLY (2)

    Hardware type: 1, Hardware address length: 6

    Hops: 0, Transaction ID: 2273587435

    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: c465-1690-2cb3

    Server host name: not configured

    Boot file name: not configured

    DHCP message type: DHCPNAK (6)

3、定位：dhcp报文不管从spine,leaf，access上的vxlan 4094接入，都会造成环路问题，  leaf上因为vxlan 4094配置了dhcp snooping trust，所以会向4094的teunnel口广播 广播到其他leaf，其他leaf同样处理又广播回来，导致dhcp报文成环 

 Vxlan4094是管理vxlan，不要接入客户端 

如果问题发生，临时规避方法可以在leaf上把vxlan 4094配置的dhcp snooping trust undo掉，恢复后再配置回去