可以在容器中通过 iproute2 查看到， eth0 的接口类型为 veth：
❯ docker run -it --rm debian:buster bash root@5facbe4ddc1e:/# ip --details addr ls 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000 link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 promiscuity 0 minmtu 0 maxmtu 0 numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535 inet 127.0.0.1/8 scope host lo valid_lft forever preferred_lft forever 20: eth0@if21: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default link/ether 02:42:ac:11:00:02 brd ff:ff:ff:ff:ff:ff link-netnsid 0 promiscuity 0 minmtu 68 maxmtu 65535 veth numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535 inet 172.17.0.2/16 brd 172.17.255.255 scope global eth0 valid_lft forever preferred_lft forever同时在宿主机中能看到对应的 veth 设备是绑定到了 docker0 网桥的：
❯ sudo brctl show bridge name bridge id STP enabled interfaces docker0 8000.0242fce99ef5 no vethea4171a 四、其他虚拟网络接口的类型除了上面介绍的这些，Linux 还支持 VLAN、VXLAN 等类型的虚拟网络接口，可通过 ip link help 查看，因为我接触的少，这里就不介绍了。
五、虚拟网络接口的速率Loopback 和本章讲到的其他虚拟网络接口一样，都是一种软件模拟的网络设备。
他们的速率是不是也像物理链路一样，存在链路层（比如以太网）的带宽限制呢？
比如目前很多老旧的网络设备，都是只支持到百兆以太网，这就决定了它的带宽上限。
即使是较新的设备，目前基本也都只支持到千兆，也就是 1GbE 以太网标准，那本文提到的虚拟网络接口单纯在本机内部通信，是否也存在这样的制约呢？是否也只能跑到 1GbE?
使用 ethtool 检查：
# docker 容器的 veth 接口速率 > ethtool vethe899841 | grep Speed Speed: 10000Mb/s # 网桥看起来没有固定的速率 > ethtool docker0 | grep Speed Speed: Unknown! # tun0 设备的默认速率貌似是 10Mb/s ? > ethtool tun0 | grep Speed Speed: 10Mb/s # 此外 ethtool 无法检查 lo 以及 wifi 的速率 网络性能实测接下来实际测试一下，先给出机器参数：
❯ cat /etc/os-release # VERSION="20210810" ... ❯ uname -a Linux legion-book 5.13.8-1-default #1 SMP Thu Aug 5 08:56:22 UTC 2021 (967c6a8) x86_64 x86_64 x86_64 GNU/Linux ❯ lscpu Architecture: x86_64 CPU(s): 16 Model name: AMD Ryzen 7 5800H with Radeon Graphics ... # 内存，单位 MB ❯ free -m total used free shared buff/cache available Mem: 27929 4482 17324 249 6122 22797 Swap: 2048 0 2048使用 iperf3 测试：
# 启动服务端 iperf3 -s ------------- # 新窗口启动客户端，通过 loopback 接口访问 iperf3-server，大概 49Gb/s ❯ iperf3 -c 127.0.0.1 Connecting to host 127.0.0.1, port 5201 [ 5] local 127.0.0.1 port 48656 connected to 127.0.0.1 port 5201 [ ID] Interval Transfer Bitrate Retr Cwnd [ 5] 0.00-1.00 sec 4.46 GBytes 38.3 Gbits/sec 0 1.62 MBytes [ 5] 1.00-2.00 sec 4.61 GBytes 39.6 Gbits/sec 0 1.62 MBytes [ 5] 2.00-3.00 sec 5.69 GBytes 48.9 Gbits/sec 0 1.62 MBytes [ 5] 3.00-4.00 sec 6.11 GBytes 52.5 Gbits/sec 0 1.62 MBytes [ 5] 4.00-5.00 sec 6.04 GBytes 51.9 Gbits/sec 0 1.62 MBytes [ 5] 5.00-6.00 sec 6.05 GBytes 52.0 Gbits/sec 0 1.62 MBytes [ 5] 6.00-7.00 sec 6.01 GBytes 51.6 Gbits/sec 0 1.62 MBytes [ 5] 7.00-8.00 sec 6.05 GBytes 52.0 Gbits/sec 0 1.62 MBytes [ 5] 8.00-9.00 sec 6.34 GBytes 54.5 Gbits/sec 0 1.62 MBytes [ 5] 9.00-10.00 sec 5.91 GBytes 50.8 Gbits/sec 0 1.62 MBytes - - - - - - - - - - - - - - - - - - - - - - - - - [ ID] Interval Transfer Bitrate Retr [ 5] 0.00-10.00 sec 57.3 GBytes 49.2 Gbits/sec 0 sender [ 5] 0.00-10.00 sec 57.3 GBytes 49.2 Gbits/sec receiver # 客户端通过 wlp4s0 wifi 网卡(192.168.31.228)访问 iperf3-server，实际还是走的本机，但是速度要比 loopback 快一点，可能是默认设置的问题 ❯ iperf3 -c 192.168.31.228 Connecting to host 192.168.31.228, port 5201 [ 5] local 192.168.31.228 port 43430 connected to 192.168.31.228 port 5201 [ ID] Interval Transfer Bitrate Retr Cwnd [ 5] 0.00-1.00 sec 5.12 GBytes 43.9 Gbits/sec 0 1.25 MBytes [ 5] 1.00-2.00 sec 5.29 GBytes 45.5 Gbits/sec 0 1.25 MBytes [ 5] 2.00-3.00 sec 5.92 GBytes 50.9 Gbits/sec 0 1.25 MBytes [ 5] 3.00-4.00 sec 6.00 GBytes 51.5 Gbits/sec 0 1.25 MBytes [ 5] 4.00-5.00 sec 5.98 GBytes 51.4 Gbits/sec 0 1.25 MBytes [ 5] 5.00-6.00 sec 6.05 GBytes 52.0 Gbits/sec 0 1.25 MBytes [ 5] 6.00-7.00 sec 6.16 GBytes 52.9 Gbits/sec 0 1.25 MBytes [ 5] 7.00-8.00 sec 6.08 GBytes 52.2 Gbits/sec 0 1.25 MBytes [ 5] 8.00-9.00 sec 6.00 GBytes 51.6 Gbits/sec 0 1.25 MBytes [ 5] 9.00-10.00 sec 6.01 GBytes 51.6 Gbits/sec 0 1.25 MBytes - - - - - - - - - - - - - - - - - - - - - - - - - [ ID] Interval Transfer Bitrate Retr [ 5] 0.00-10.00 sec 58.6 GBytes 50.3 Gbits/sec 0 sender [ 5] 0.00-10.00 sec 58.6 GBytes 50.3 Gbits/sec receiver # 从容器中访问宿主机的 iperf3-server，速度几乎没区别 ❯ docker run -it --rm --name=iperf3-server networkstatic/iperf3 -c 192.168.31.228 Connecting to host 192.168.31.228, port 5201 [ 5] local 172.17.0.2 port 43436 connected to 192.168.31.228 port 5201 [ ID] Interval Transfer Bitrate Retr Cwnd [ 5] 0.00-1.00 sec 4.49 GBytes 38.5 Gbits/sec 0 403 KBytes [ 5] 1.00-2.00 sec 5.31 GBytes 45.6 Gbits/sec 0 544 KBytes [ 5] 2.00-3.00 sec 6.14 GBytes 52.8 Gbits/sec 0 544 KBytes [ 5] 3.00-4.00 sec 5.85 GBytes 50.3 Gbits/sec 0 544 KBytes [ 5] 4.00-5.00 sec 6.14 GBytes 52.7 Gbits/sec 0 544 KBytes [ 5] 5.00-6.00 sec 5.99 GBytes 51.5 Gbits/sec 0 544 KBytes [ 5] 6.00-7.00 sec 5.86 GBytes 50.4 Gbits/sec 0 544 KBytes [ 5] 7.00-8.00 sec 6.05 GBytes 52.0 Gbits/sec 0 544 KBytes [ 5] 8.00-9.00 sec 5.99 GBytes 51.5 Gbits/sec 0 544 KBytes [ 5] 9.00-10.00 sec 6.12 GBytes 52.5 Gbits/sec 0 544 KBytes - - - - - - - - - - - - - - - - - - - - - - - - - [ ID] Interval Transfer Bitrate Retr [ 5] 0.00-10.00 sec 58.0 GBytes 49.8 Gbits/sec 0 sender [ 5] 0.00-10.00 sec 58.0 GBytes 49.8 Gbits/sec receiver