The reMarkable shows as an Ethernet device when plugged into a computer via USB. It runs a DHCP server and will listen on 10.11.99.1 by default, assigning IP addresses in the 10.11.99.2 to 10.11.99.6 range (see also 修改usb模式下的ip地址). The DHCP server configuration is in /etc/udhcpd.usb0.conf and the network configuration is in /usr/lib/systemd/network/rndis.network.