IPv4 Private IP address ranges
The private IPv4 address ranges are:
- Class A: 10.0.0.0 – 10.255.255.255
- Class B: 172.16.0.0 – 172.31.255.255
- Class C: 192.168.0.0 – 192.168.255.255
These addresses are defined in RFC 1918 as private IPv4 addresses and can be freely used for internal networks. It is always best practice to use these ranges for internal networks, because they are not routable on the Internet.
By using these addresses you avoid IP address duplication within your network with addresses that may exist on the Internet. If an address assigned to a host on the internal network also exists on the Internet, you would never be routed to the Internet, but you would be routed internally to the device with that IP address.
For this reason, it is always good to use these private IP address ranges for internal networks, so that you can make sure that there is no conflict. You know that these will never exist on the Internet, and even if you try to send a packet with such an address on the Internet, the routers are designed to drop all such packets.
Links
Links to this page:
- ASA NAT translate_hits and untranslate_hits counters
- BGP - IGP-BGP redistribution best practices
- BGP - using private ASNs with private IPs
- Carrier-Grade NAT
- Hardware - Application Specific Integrated Circuit (ASIC)
- IPv6 - Site Local addresses
- IPv6 - Unique Local addresses
- NAT - Translation Table
- NAT - Virtual Interface (NVI)
- NAT - What is Policy NAT
- NAT - translate address not directly connected to edge device
- NAT Extendable on Cisco IOS
- Network Address Translation (NAT)
- Security - bogons