Upgrading from 17.01 to 22.03.0 by doing a clean install. Everything had been working fine in 17.01, just needed to upgrade because (insert stern warnings here).
Now cannot get my Linksys WRT1900ACS router to get an DHCP IP address from my SMC D3CM1604 Modem (ISP is Comcast). However, If I directly connect PC to the modem all works good, albeit takes a bit longer.
Is there a way to extend the timeout that OpenWrt takes in asking for a DHCP IP address from the WAN/Modem?
With cable modems, you usually need to restart the modem (sometimes several times) to clear the MAC address binding. The modem will only issue an IP to the previously learned MAC address until it it is rebooted.
Ideally, your router would always have the same MAC, but a few things are possible here:
the upgrade from 17.01 > 22.03 may have caused the MAC address for the WAN and LAN to be reversed. (it's not the upgrade itself, but rather that the way OpenWrt reads/assigns the MAC addresses might have changed in one of the intermediate versions (possibly correcting a bug).
You connected your computer, so the modem learned that MAC and bound to it.
Either way, restart your modem and then plug it the router and you should be good to go.