Network Address Calculator
Find the network address for any IP and subnet mask
Input CIDR Addresses
The network address is calculated by applying the subnet mask to the IP address, zeroing out the host bits.
Network Addresses
Network addresses will appear here
The Network Address Calculator finds the network address (also called the network ID) for any IP address and subnet mask combination. Enter an IP like 192.168.1.45/24 to instantly compute the base network address, which identifies the subnet that the host belongs to.
Understanding Network Addresses
The network address is the foundation of how IP routing works. Every subnet has one, and it is always the first address in the range -- the address where all the host bits are set to zero. When you write 192.168.1.0/24, the .0 at the end is the network address, and it tells routers, firewalls, and every other device on the network that this is the identity of that particular subnet, not a host you can send traffic to.
Why does this matter for your daily work? Because nearly everything you configure references network addresses. Static routes point to network addresses (ip route 10.0.0.0 255.255.0.0 192.168.1.1). Firewall rules match on network addresses to allow or deny entire subnets. DHCP servers use the network address to define the boundaries of their scopes. Even simple tasks like documenting your infrastructure require knowing the network address for each VLAN and segment. If you give a host the network address by mistake, that host will be invisible on the network because its address is reserved for identifying the subnet itself.
The calculation is simple in concept -- perform a bitwise AND between the IP address and the subnet mask -- but it gets tricky when the prefix does not land on an octet boundary. For a /20 or /26, the masking splits within an octet, and mental arithmetic in binary is error-prone. This calculator handles all prefix lengths and shows the binary breakdown so you can see exactly how the masking works.
How to Find the Network Address for Any IP
- Enter an IP address with CIDR notation (e.g.,
192.168.1.45/24) or an IP with a dotted decimal mask - The calculator performs a bitwise AND between the IP address and the subnet mask
- The host portion of the address is zeroed out, leaving only the network portion
- The resulting network address is displayed in both standard and CIDR notation
Network Address Calculation Examples
| Input IP | Prefix | Network Address | How It Works |
|---|---|---|---|
192.168.1.45 | /24 | 192.168.1.0 | Host bits (last 8) zeroed: .45 becomes .0 |
10.25.130.200 | /8 | 10.0.0.0 | Host bits (last 24) zeroed |
172.16.5.130 | /20 | 172.16.0.0 | Third octet 5 (binary 00000101) masked by 11110000 = 0 |
192.168.10.67 | /28 | 192.168.10.64 | Last 4 bits zeroed: 67 (binary 01000011) becomes 01000000 = 64 |
10.1.1.3 | /30 | 10.1.1.0 | Last 2 bits zeroed: 3 (binary 11) becomes 00 = 0 |
172.16.130.50 | /16 | 172.16.0.0 | Host bits (last 16) zeroed |
When to Use This Tool
- Configuring static routes -- routes specify network addresses and masks, not individual host IPs
- Writing firewall rules -- many rules reference network addresses to permit or deny entire subnets
- Setting up DHCP scopes -- DHCP servers need the network address to define the scope boundary
- Troubleshooting routing -- verify which network a host IP belongs to and whether it matches the expected route
- Documenting networks -- record each subnet using its canonical network address and prefix
- Validating subnet membership -- confirm that a given IP belongs to a specific network before configuring it
How Network Address Calculation Works
The Bitwise AND Operation
The network address is calculated by ANDing each bit of the IP address with the corresponding bit of the subnet mask. Only bits where both the IP and mask are 1 remain 1 in the result.
IP Address: 192.168.1.45 → 11000000.10101000.00000001.00101101
Subnet Mask: 255.255.255.0 → 11111111.11111111.11111111.00000000
AND ─────────────────────────────────────────────────
Network Addr: 192.168.1.0 → 11000000.10101000.00000001.00000000
Non-Octet Boundary Example (/20)
When the prefix does not fall on an octet boundary, the masking splits within an octet:
IP Address: 172.16.5.130 → 10101100.00010000.00000101.10000010
Subnet Mask: 255.255.240.0 → 11111111.11111111.11110000.00000000
AND ─────────────────────────────────────────────────
Network Addr: 172.16.0.0 → 10101100.00010000.00000000.00000000
The third octet 5 (binary 00000101) ANDed with 240 (binary 11110000) yields 0 (binary 00000000).
Why Routers Calculate Network Addresses
When a router receives a packet, it examines the destination IP and performs the same bitwise AND against each entry in its routing table. The result determines which route matches and which interface forwards the packet. This is the core of the longest prefix match algorithm that drives IP routing.
Network Address vs. Host Address
| Term | Meaning | Example (/24) |
|---|---|---|
| Network address | First address in subnet, all host bits 0 | 192.168.1.0 |
| Host address | Any assignable address in the range | 192.168.1.1 -- 192.168.1.254 |
| Broadcast address | Last address in subnet, all host bits 1 | 192.168.1.255 |
The network address cannot be assigned to a host. It identifies the subnet as a whole and appears in routing tables, ACLs, and network diagrams.
Network Addressing in Practice
One of the most common mistakes in network configuration is accidentally assigning the network address to a device. If you configure a server with 192.168.1.0/24 thinking that .0 is just another usable address, the server will have routing problems and may be unreachable. Some operating systems will accept this configuration without warning, but traffic destined for the subnet itself will conflict with the host. Always start assigning host addresses from the network address plus one.
Another area where network address knowledge pays off is in troubleshooting. When a user reports that they cannot reach a server, one of the first things to check is whether the client and server are on the same subnet. Calculate the network address for both devices -- if they differ, the traffic has to cross a router, and the problem might be a missing route, a firewall rule, or a gateway misconfiguration. If the network addresses match but connectivity still fails, the issue is likely at layer 2 (VLAN tagging, switch port assignment, or ARP).
When documenting your network, always record subnets using the network address rather than an arbitrary host address. Writing "the accounting VLAN is 192.168.5.0/24" is unambiguous, while writing "the accounting VLAN is 192.168.5.100/24" is confusing -- other engineers have to calculate the network address themselves to understand the subnet boundaries. Using canonical network addresses in your documentation, IPAM tools, and configuration management makes everything clearer and reduces errors during changes.
Frequently Asked Questions
What is the network address of 10.0.50.100/16?
For 10.0.50.100/16, the subnet mask is 255.255.0.0. The bitwise AND zeroes out the last two octets: 10.0.50.100 AND 255.255.0.0 = 10.0.0.0. So the network address is 10.0.0.0.
Can a host use the network address?
No. The network address (all host bits set to 0) is reserved to identify the subnet itself. Assigning it to a device would cause routing ambiguity. Similarly, the broadcast address (all host bits set to 1) is reserved for sending traffic to all hosts on the subnet. The only exception is /31 (RFC 3021) and /32 networks.
How is the network address different from the default gateway?
The network address identifies the subnet (e.g., 192.168.1.0/24), while the default gateway is a specific host address on the subnet (commonly 192.168.1.1) that routes traffic to other networks. The gateway must be a usable host address within the subnet, not the network address itself.
What happens if I configure a device with the network address?
The device may appear to work initially, but it will likely experience intermittent connectivity issues. Routing tables use the network address to identify the subnet as a whole, so a host using that address creates ambiguity. Some devices will refuse the configuration, while others will accept it silently and then behave unpredictably. Always use a host address within the usable range instead.
How do I find the network address for a /28 subnet?
For any IP in a /28, the last 4 bits are host bits. To find the network address, zero out those 4 bits. For example, 10.0.0.67/28: 67 in binary is 01000011, zeroing the last 4 bits gives 01000000 = 64, so the network address is 10.0.0.64. The subnet covers addresses 10.0.0.64 through 10.0.0.79.
Related Tools
- IPv4 Subnet Calculator - Calculate network, broadcast, and host range from CIDR notation
- Broadcast Address Calculator - Find the broadcast address for any subnet
- First/Last Usable Host Calculator - Find the first and last usable host addresses in a subnet
- Netmask ↔ CIDR Converter - Convert between subnet mask notation and CIDR prefix length
- IP in Subnet? Checker - Check if an IP address belongs to a specific subnet
- Wildcard Mask Calculator - Calculate wildcard masks for ACLs and routing protocols