Ubuntu 22.04系统中arp命令输出疑问及USB以太网适配器相关问题咨询

我之前查过资料，了解到arp命令是用来显示IP地址和MAC地址之间的映射关系的，但在Ubuntu 22.04系统上看到的输出让我有点困惑。

我的arp命令输出如下：

_gateway (192.168.107.172) at 3a:65:d4:6d:20:cf [ether] on wlp0s20f3

我原本以为这个输出表示：有一个MAC地址为3a:65:d4:6d:20:cf的以太网适配器，对应的IP地址是192.168.107.172。但当我运行ifconfig查看本地网络配置时，却找不到这个IP地址：

enp84s0: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
        ether 7c:57:58:80:1c:61  txqueuelen 1000  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
        device memory 0x54000000-540fffff

enx00e04c680202: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.200.100  netmask 255.255.255.0  broadcast 192.168.200.255
        ether 00:e0:4c:68:02:02  txqueuelen 1000  (Ethernet)
        RX packets 124  bytes 11140 (11.1 KB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 28  bytes 2981 (2.9 KB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

enxa0cec8c97ebc: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
        ether a0:ce:c8:c9:7e:bc  txqueuelen 1000  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 13849  bytes 1664000 (1.6 MB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 13849  bytes 1664000 (1.6 MB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

wlp0s20f3: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.107.238  netmask 255.255.255.0  broadcast 192.168.107.255
        inet6 fe80::6a85:ef4a:7e3c:be96  prefixlen 64  scopeid 0x20<link>
        inet6 2a01:cb16:2068:7c6c:8e00:94e:c979:548e  prefixlen 64  scopeid 0x0<global>
        inet6 2a01:cb16:2068:7c6c:d2f4:5a68:7bd8:e5d7  prefixlen 64  scopeid 0x0<global>
        ether 3c:e9:f7:a7:1c:0f  txqueuelen 1000  (Ethernet)
        RX packets 209228  bytes 203369040 (203.3 MB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 113025  bytes 26069725 (26.0 MB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

我注意到arp输出里提到的网卡wlp0s20f3，它的IP地址是192.168.107.238，而不是192.168.107.172，这和我之前的理解完全不符，实在想不通是怎么回事。

另外，我还使用了一个USB以太网适配器（enx00e04c680202），但它并没有出现在arp的输出列表里。我想问的是：USB以太网适配器难道没有MAC地址吗？

我已经查了不少相关资料，但始终没找到能解答这些疑问的答案，希望有人能帮我理清这些问题。

备注：内容来源于stack exchange，提问作者Alex