Addresses and Subnet Masks
INFO
This is all for IPv4. IPv6 is not discussed in this guide.
IP Addresses
IP addresses are 32-bit numbers, commonly represented as 4 octets, written in decimal notation.
EXAMPLE
192.168.1.35 - decimal notation
11000000.10101000.00000001.00100011 - binary representation of the same address
We generally work in private networks called LANs, which are commonly limited to 192.168.X.X or 10.X.X.X, among other options. (To learn more, look into "RFC 1918 addresses" - address allocation for private networks).
192.168.X.X is the factory-default address range on most products.
WARNING
Constantly typing 192.168.X.X is a waking nightmare which can easily be avoided by using 10.0.X.X instead.
Friends don't let friends use 192.168.X.X.
Under the hood, IP addresses have two parts - a network address and a host address. These two portions are separated according to the subnet mask.
Subnet Masks
Subnet masks indicate how many bits within an IP address are allocated to the network address vs the host address.
Reserved addresses
Within a subnet, two (or three) addresses are reserved for special use and should be avoided.
| Address | Example | Use | Notes |
|---|---|---|---|
| All bits off | 10.0.1.0/24 | Network Address | Used to describe the network, and may not be used for a host. |
| First usable address | 10.0.1.1/24 | Default Gateway | This is not a hard rule, but is common practice, and I recommend not using this address for anything other than a gateway/router. |
| All bits on | 10.0.1.255/24 | Broadcast Address | Packets sent to this address will be sent to all hosts within the subnet. |
Subnet masks are typically represented in decimal notation (255.255.255.0) or CIDR notation ([IP Adddress]/24).
| Binary | Decimal | Suffix | Host Addresses |
|---|---|---|---|
11111111.00000000.00000000.0000000 | 255.0.0.0 | /8 | 16,777,214 |
11111111.11111111.00000000.0000000 | 255.255.0.0 | /16 | 65,534 |
11111111.11111111.11111110.0000000 | 255.255.254.0 | /23 | 510 |
11111111.11111111.11111111.0000000 | 255.255.255.0 | /24 | 253 |
In live sound systems, we almost always use "three octets masked", denoted as 255.255.255.0 or /24, because our networks do not typically have enough hosts to necessitate more available address space. (Obviously there are exceptions out there.)
This means that the first three octets of the IP address are the "subnet", and should match, while the last octet is the "address", and should be unique.
TIP
On older versions of macOS, you could type /24 at the end of the IP address field in System Preferences, and it would auto-fill the subnet mask and default gateway for you. Sadly, this was discontinued in the horrible System Preferences overhaul of macOS 12.