I've been watching the Networking Services/Applications videos and I have a query about DHCP.
I get that if you have a simple one subnet network with a single DHCP server and a single DHCP scope it is pretty straightforward to assign addresses to DHCP hosts.
However, I'm curious as to how this works when you have a network with multiple subnets. For example, lets say we have Subnet A, Subnet B and Subnet C and all hosts on all 3 subnets are using a single DHCP server located on Subnet A. Assuming a DHCP relay is configured on the router/s for Subnet B and Subnet C, and the DHCP server has 3 scopes created that correlate with the IP addressing scheme on the 3 subnets, how does the server know to hand out the correct IP addresses from the correct scope to the correct hosts? Is there some sort of config that says only assign Scope A addresses to the local subnet and send Scope B addresses to hosts connected to router interface B, Scope C addresses to hosts connected to router interface C.....etc?
Also, if you have very large network with lots of subnets and you have multiple DHCP servers in different subnets, if a host's local DHCP server goes down, and assuming you have DHCP relays set up, the host should get a DHCP address from an alternative DHCP server that is first to reply to the broadcast for an address, But what if the server that responds doesn't have the correct scope set up for that particular subnet? Will it simply not be able to get an address at all and therefore assign itself an APIPA address, or will it be assigned an incorrect address from the scope configured on the alternate DHCP server?
Hope all of that makes sense!