Static and dynamic assignment
- Static: set manually; use for servers, routers, printers.
- Dynamic: leased by a DHCP server; use for clients.
Choosing static or DHCP
| Device | Usual choice | Why |
|---|---|---|
| Servers, routers, printers, switches' management IPs | Static | Other devices and DNS records must find them at a fixed address |
| Laptops, phones, lab PCs | DHCP | Easy to manage; addresses are leased and returned automatically |
Static addresses must still be outside the DHCP pool (or reserved in DHCP) so two devices never get the same IP. Duplicate IPs cause intermittent "destination unreachable" faults that are hard to spot.
Unicast, broadcast, multicast
Unicast is one-to-one; broadcast is one-to-all on the subnet (sent to the subnet's broadcast address, which is the last address in the subnet); multicast is one-to-many group.
Delivery types in more detail
- Unicast: one sender, one receiver. Normal web browsing, SSH and file transfers are unicast.
- Broadcast: one sender, every host on the local subnet. DHCP discover and ARP requests use broadcast. Routers do not forward broadcasts to other networks (that is one reason we subnet: to limit broadcast traffic).
- Multicast: one sender, only hosts that joined a group (for example IPTV or some routing protocols). Multicast addresses are in
224.0.0.0–239.255.255.255.
The subnet broadcast address is the last address in the subnet (all host bits set to 1). For 192.168.10.0/24 it is 192.168.10.255. Hosts must not use the network address (all host bits 0) or the broadcast address as their own IP.
Remember
- Static for infrastructure; DHCP for clients; never overlap pools.
- Broadcast stays on one subnet; that is why subnet size affects noise and performance.
- Unicast = one, broadcast = all on subnet, multicast = a group.