A /30 has four addresses: network, two hosts and broadcast. Mask 255.255.255.252. For decades it was the standard size for a link between two routers, since such a link needs exactly two addresses. Many networks now use /31s instead to save the two wasted addresses. In a /30 like 10.0.0.0/30, the hosts are 10.0.0.1 and 10.0.0.2.
Facts
- Prefix
- /30
- Subnet mask
- 255.255.255.252
- Wildcard mask
- 0.0.0.3
- Binary mask
- 11111111.11111111.11111111.11111100
- Total addresses
- 4
- Usable hosts
- 2
- Example range
- 192.168.1.0/30: 192.168.1.0 – 192.168.1.3
- Typical use
- Point-to-point links between two routers.
Try it
Try: , ,
- CIDR block
- 192.168.1.0/30
- IP range
- 192.168.1.0 – 192.168.1.3
- Addresses
- 4
- Usable hosts
- 2
- Subnet mask
- 255.255.255.252
- Wildcard mask
- 0.0.0.3
Frequently asked questions
How many hosts are in a /30?
A /30 has 4 addresses. Subtracting the network and broadcast addresses leaves 2 usable hosts.
What is the subnet mask for /30?
/30 is 255.255.255.252 (wildcard mask 0.0.0.3). In binary that’s 30 ones followed by 2 zeros.