I try to connect my CISCO Cable Modem to my Redmi AC2100 with OpenWRT 21.02.0 RC4.
The problem, I cant get anything back from my modem (for sure, I have restarted it also, before switch it to a other device, that MAC Address learned is cleared). But there is no DHCP answer from the modem.
I also tested to remove lan3 from br-lan and switched wan interface to lan3 device. Same problem.
I know, that cable modems have such problems with vlan - I also was at some customers and I tried to connect the cable modem over a VLAN, but was never able to get a IP Address from it.
I captured the process with tcpdump and analyzed it with wireshark, but could not find any problem.
I have a second OpenWRT Router (TP-Link Archer C2600) with OpenWRT 19.07.7 and there I am be able to connect to the Internet.
Has someone any hint what I can try to fix my problem?
I think it has something to do with the new DSA switch config interface.