📋

DHCP Relay & Snooping

Medium

Free preview · 2 of 6 steps

DHCP relay: crossing subnet boundaries

DHCP uses broadcast to find a server. But routers don't forward broadcasts — a client in VLAN 10 can't reach a DHCP server in a different subnet.

DHCP relay agents (configured on routers with ip helper-address) intercept DHCP broadcasts and forward them as unicast to the central DHCP server. The server knows which subnet to assign from by reading the giaddr field.

Packets in motion — click to inspect:

1 / 2

Space to play/pause · ← → to step