ChorusOS systems may support multiple Ethernet devices that all have their own Ethernet interface. See the appropriate guide in the ChorusOS 4.0 Target Family Documentation Collection for the list of supported Ethernet devices for your particular target system hardware.
If you are unsure which Ethernet device your system uses, yet you are able to boot the system, you can use the dtree(1M) utility to display devices listed in the target system device tree:
$ rsh target dtree
A ChorusOS system often uses the Ethernet interface in conjunction with the Dynamic Host Configuration Protocol (DHCP) client or Reverse Address Resolution Protocol (RARP) to obtain an IP address at boot time. As the system runs, it uses the Address Resolution Protocol (ARP) to find the Ethernet addresses of other systems, based on their IP addresses.