Trying to configure a Mikrotik Routerboard, I found that when booting SwOS, DHCP does not work. That is, the Routerboard, in my case a Cloud Router Switch CRS 317-1G-16S+, would send out DHCP requests but not get an IP address.

Turns out this is because the DHCP client of SwOS 2.7 is picky, and the dnsmasq DHCP server sent an offer that was not accepted by SwOS.

Using udhcpd as a dhcp server instead, the switch accepted the IP address just fine. I could then update the firmware; from 2.8 on, the SwOS DHCP client is more tolerant of DHCP offers. One of the changes in the SwOS 2.8 release notes says ‘make DHCP client work with RFC non compliant DHCP servers’. At any rate, 2.9 was happy with dnsmasq DHCP offers.