FAQ

Why does the log say it is using a synthetic interface?

When no host adapter holds the address a datagram arrived on, the listener hands the handler a placeholder interface (unknown[<address>], a /32 with no MAC) and logs one WARNING for each address. A server cannot derive an address pool from a /32, so it answers nothing from it. The usual cause is a listener bound to an address that the host's adapters do not list; name an address or an adapter that the host has (pydhcp interfaces lists them).

Why are some clients sent broadcast replies?

A client with no address yet cannot answer ARP for the one it was offered, so a reply unicast to it on a plain UDP socket is lost without an error. The server therefore answers such a client by broadcast, whether or not its BROADCAST flag is set, and a DHCPNAK with no relay is always broadcast. The exceptions are an exchange over loopback, where there is no ARP and POSIX refuses the broadcast, and a server with UNICAST_TO_UNCONFIGURED_CLIENT set. A send that fails is never retried as a broadcast: it raises OSError.

How do I run a DORA handshake from Python?

Use DHCPClient.dora() — it broadcasts a DHCPDISCOVER, waits for a DHCPOFFER, sends a matching DHCPREQUEST, and waits for the DHCPACK, raising DHCPTimeoutError if no usable reply arrives after the configured retries (or the call's deadline) and DHCPRefusedError if the server answers with a DHCPNAK. The client's listener loop must be started first (client.start()) so replies reach its internal queue. See Examples for a full snippet, or DHCPClient.discover_offer() if you only need the offer.

Which config formats does the CLI accept?

pydhcp --config FILE server (or PYDHCP_CONFIG) accepts JSON, TOML, YAML or INI, selected by the file's ending (.json, .toml, .yaml, .yml, .ini, .cfg). TOML needs Python 3.11+ (stdlib tomllib) or duho[config] on older versions, YAML duho[yaml]. See Examples.