I have a bunch of WR21s that are all showing the same behavior.
I put the units into port isolate mode,
I assign 192.168.51.9/29 to Eth 0,
I set Eth1 to DHCP and it refuses to pick up a DHCP address.
I’ve duplicated this behavior on 3 different WR21s (all so far) and from the DHCP service from an ADSL router and a Windows server on an office LAN. Same behavior, Eth1 refuses to pick up a DHCP address.
Is this normal behavior when in port isolate mode?
That should work in Port Isolated mode. Have you rebooted the unit after put them in Port Isolated so that the change is applied?
If you put back to HUB, does it works?
Is there a switch between the ETH1 port and the DHCP server?
Without seeing the complete config and status as well as the firmware version running, Is not easy to understand what is happening. So, I would suggest you to open a case sending an email to tech.support@digi.com so we can properly troubleshoot. Please include a backup file from the unit (Administration > Backup/Restore) being sure to include the debug.txt file in it. Also, please provide the IMEI of the router for warranty check.