The Internet forums would have you believe that USB-based ethernet adaptors aren’t good enough if you’re performance conscious. I’m planning to deploy an Intel NUC mini-PC as a home router/firewall. NUCs only have one ethernet adaptor built in, but have USB3 ports.
I naturally wanted to find out what performance I might be sacrificing if I used a USB3 port as the second LAN port on the NUC, so I got an Anker-branded USB3 to Ethernet adaptor, plugged it into a laptop, and configure iperf3 as a server on my desktop.
Connecting to host 192.168.1.125, port 5201 [ 4] local 192.168.1.98 port 54918 connected to 192.168.1.125 port 5201 [ ID] Interval Transfer Bandwidth [ 4] 0.00-1.00 sec 106 MBytes 886 Mbits/sec [ 4] 1.00-2.00 sec 104 MBytes 871 Mbits/sec [ 4] 2.00-3.00 sec 93.5 MBytes 784 Mbits/sec [ 4] 3.00-4.00 sec 106 MBytes 886 Mbits/sec [ 4] 4.00-5.00 sec 103 MBytes 866 Mbits/sec [ 4] 5.00-6.00 sec 102 MBytes 858 Mbits/sec [ 4] 6.00-7.00 sec 106 MBytes 886 Mbits/sec [ 4] 7.00-8.00 sec 104 MBytes 873 Mbits/sec [ 4] 8.00-9.00 sec 108 MBytes 908 Mbits/sec [ 4] 9.00-10.00 sec 111 MBytes 931 Mbits/sec
The performance speaks for itself. It works just as good as the built-in ethernet card.
Don’t be swayed by vague claims about the suitability of USB ethernet adaptors for use in homebrew routers. They seem fine for the task.