Zeroconf vs. DHCP?

bloodshotbetty

So, I understand that DHCP assigns IP, default gateway, etc etc. And zeroconf auto configs network addresses, distribution/resolution of host names, and auto locates network services.

It seems like zeroconf would work in conjunction with DHCP, but what is the main difference? If DHCP assigns network addresses, why use zeroconf to do the same thing? Does zeroconf work to configure private addresses?

Thanks in advance for the help.

OctalDump

Zeroconf is a set of services, and yes can work in conjuction with DHCP. The main use of DHCP is to provide the client with 4 things: IP address, subnet mask, Default Gateway, DNS servers. It has another ~200 options for a whole range of other things.

Zeroconf can provide network addresses, but only in the link-local address space (169.254.x.x and fe80::/10), which means they cannot be routed ie cannot connect to other networks including the internet. This isn't a problem if you just want to share a file between two computers or connect to a printer, but for 90% of what people want to do, it's not very useful. So, DHCP is a better option for addressing.... at least as far as IPv4 is concerned. Things are much better with IPv6

The real strengths of Zeroconf, and the way it complements greatly DHCP, is in using multicast name resolution protocols and service discovery. This means that a computer on a network can discover a whole range of services, far more than DHCP since it is extensible. In a sense this can be thought of as an analog of DNS and service records. Again, it is primarily of local significance - for finding hosts, services, and resources on the local network. You would still use DNS for the internet as a whole, and for anything where security (an authoritative, trusted source) is important since the distributed nature of zeroconf makes it very vulnerable to spoofing attacks.


So, DHCP + DNS gives you a centralised and trusted way of providing addresses, names, host resolution and service discovery. Zeroconf gives you a distributed, less secure, less controlled way of providing (local only) addresses, names, host resolution and service discovery.