What Is Broadcast?
Broadcast — a transmission sent to every device on a network segment at once — addressed to all, processed by all.
How it works
Layer 2 broadcasts use destination MAC FF:FF:FF:FF:FF:FF; IPv4 uses the subnet's broadcast address (e.g. 192.168.1.255 for /24). ARP requests and DHCP Discovers are everyday broadcasts. Switches flood them out all ports; routers stop them — which is why a router boundary defines a broadcast domain.
Why it matters
Too many devices in one broadcast domain drowns everyone in chatter — the core reason VLANs exist. Note IPv6 dropped broadcast entirely in favour of targeted multicast.
Frequently asked questions
What is a broadcast address?
A special address meaning 'every host here': FF:FF:FF:FF:FF:FF at Layer 2, or the subnet's highest address (like 192.168.1.255/24) in IPv4.
Do routers forward broadcasts?
No — routers bound broadcast domains, which is exactly why segmenting networks reduces broadcast noise.
Does IPv6 have broadcast?
No — IPv6 replaces broadcast with multicast groups (like all-nodes FF02::1) so only interested devices process traffic.
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