This is an old revision of the document!
Debian deprecated isc-dhcp-client and replaced it dhcpcd. It took me a bit to figure out how to regulate dhcpcd so it stopped messing with my gateways and dns. Open up sudo nano /etc/dhcpcd.conf and comment out and/or enter the following:
# comment out requesting dns stuffs from router
#option domain_name_servers, domain_name, domain_search
# stop it from messing with resolv.conf
nohook resolv.conf
# stop IoT bridges on vlans/subnets from creating gateways or routes
interface br2
nogateway
# stop IoT bridges on vlans/subnets from creating gateways or routes
interface br3
nogateway
Once this is done, you make sure Network Manager is managing ifupdown by sudo nano /etc/NetworkManager/NetworkManager.conf:
[main] plugins=ifupdown,keyfile [ifupdown] managed=true
Then, lastly, you also need to stop Network Manager from messing with DNS. So, first, disable ipv4 and ipv6 on the ethernet interfaces in nm-connection-editor. This stops the interfaces themselves from getting an IP from Network Manager. We don't want this because ifupdown already gives the same subnet an address on the bridge, so no need for the interface to also have an address. Additionally, it can cause gateway issues.
Then, lastly, you want to turn on “address only” mode for all the managed bridges in Network Manager.
