Is there a protocol for that switches, or devices with multiple network ports, could use to signal link changes, or some mean to try to detect link changes? The scenario I'm trying to solve is scenarios where devices can try to start using link local addressing when there is no DHCP server present, and to try to detect when DHCP server becomes available.
I realize this sounds a bit vague, so I'll try to clarify. When the devices below acquires a network link, they will first try to configure using DHCP, and if that not works they will fall back and use link local addressing (169.254.0.0/16)
switch 1 -- switch 2 -- switch 3 `- dev1 `- dev2 `- dev3
But if I connect a DHCP server to the network, I want the devices to reconfigure their network settings and use the addresses provided by the DHCP server. I also want to be able to detect when a link somewhere in the chain goes down (powerloss or something), and allow the isolated group reconfigure their network settings using link local addressing. I would also like to detect when two groups are connected again, so they can advertise their presence to each other.
So, I'm looking for some kind of protocol that can provide information about the link status for the switches. I'll look into the spanning tree protocol.