从 bond0 中删除 eth0 修复了 Link 检测到否/是的问题，但为什么呢？

Question

在具有 4 个物理 NIC 的 SLES12 上，将它们置于 bond0 中。

eth0 显示“检测到链接：否”。

但是如果我从 bond0 中删除 eth0 并执行“ifup eth0”，它将显示“检测到链接：是”并且 eth0 上的一切看起来都很好：

前：

SERVER:/etc/sysconfig/network # ethtool eth0
Settings for eth0:
        Supported ports: [ FIBRE ]
        Supported link modes:   10000baseT/Full
        Supported pause frame use: No
        Supports auto-negotiation: No
        Advertised link modes:  10000baseT/Full
        Advertised pause frame use: No
        Advertised auto-negotiation: No
        Speed: Unknown!
        Duplex: Unknown! (255)
        Port: Direct Attach Copper
        PHYAD: 0
        Transceiver: external
        Auto-negotiation: off
        Supports Wake-on: umbg
        Wake-on: g
        Current message level: 0x00000007 (7)
                               drv probe link
        Link detected: no
SERVER:/etc/sysconfig/network # 

从 bond0 中删除 eth0：

SERVER:/var/log # ifenslave -d bond0 eth0
SERVER:/var/log # ifup eth0 # this re-adds the eth0 to the bond0

后：

SERVER:/etc/sysconfig/network # ethtool eth0
Settings for eth0:
        Supported ports: [ FIBRE ]
        Supported link modes:   10000baseT/Full
        Supported pause frame use: No
        Supports auto-negotiation: No
        Advertised link modes:  10000baseT/Full
        Advertised pause frame use: No
        Advertised auto-negotiation: No
        Speed: 10000Mb/s
        Duplex: Full
        Port: Direct Attach Copper
        PHYAD: 0
        Transceiver: external
        Auto-negotiation: off
        Supports Wake-on: umbg
        Wake-on: g
        Current message level: 0x00000007 (7)
                               drv probe link
        Link detected: yes
SERVER:/etc/sysconfig/network #

大问题: 什么会导致这种行为？

看起来这不是物理问题，而是一些配置或错误？

更新：在交换机端检查，配置看起来没问题！