Reserved & Special-Use IP Addresses
Special-purpose IP ranges you'll encounter in network design.
Beyond the private ranges of RFC 1918, several IPv4 blocks are reserved for specific purposes by the IANA: loopback (127.0.0.0/8), link-local or APIPA addressing (169.254.0.0/16), carrier-grade NAT (100.64.0.0/10), the TEST-NET documentation ranges, multicast, and the limited broadcast address.
Knowing these ranges prevents real mistakes - assigning a documentation address into production, or treating an APIPA address as a valid client assignment.
| CIDR / Address | Name | RFC | Use |
|---|---|---|---|
| 0.0.0.0/8 | "This" network | RFC 1122 | Local host identification |
| 127.0.0.0/8 | Loopback | RFC 1122 | Local loopback (127.0.0.1) |
| 169.254.0.0/16 | Link-local / APIPA | RFC 3927 | Automatic addressing when DHCP fails |
| 100.64.0.0/10 | CGNAT / Shared Address Space | RFC 6598 | Carrier-grade NAT |
| 192.0.2.0/24 | TEST-NET-1 | RFC 5737 | Documentation and examples |
| 198.51.100.0/24 | TEST-NET-2 | RFC 5737 | Documentation and examples |
| 203.0.113.0/24 | TEST-NET-3 | RFC 5737 | Documentation and examples |
| 224.0.0.0/4 | Multicast | RFC 5771 | IPv4 multicast |
| 240.0.0.0/4 | Reserved (Class E) | RFC 1112 | Future use / experimental |
| 255.255.255.255 | Limited Broadcast | RFC 919 | Broadcast to local network |
More Reference
Explore the other reference in the toolkit.
RFC 1918 Private IP Ranges
RFC 1918 defines the private IPv4 ranges 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16. See each range, host count, and common use.
Common TCP & UDP Ports
Reference list of common TCP and UDP ports: SSH, DNS, HTTP, HTTPS, SMTP, NTP, DHCP, SNMP, RDP, and more, with protocols and descriptions.
Fiber Connector Types
Reference guide to fiber optic connector types: LC, SC, ST, FC, MPO/MTP, and E2000 with polish, return loss, and typical use.
Ethernet Standards (IEEE 802.3)
Reference table of IEEE 802.3 Ethernet standards: 1000BASE-T, 10GBASE-T, 10GBASE-SR/LR, 25G, 40G, 100G, and 400G with media and distances.
RFC References for Network Engineers
Quick reference list of the essential networking RFCs every infrastructure engineer should know, from RFC 1918 to BGP, DHCP, DNS, and NTP.
Cable Color Codes (TIA-606)
TIA-606 cable color codes for structured cabling: blue for horizontal cabling, orange for demarcation, purple for common equipment, and more.
Transceiver Form Factors
Reference table of optical transceiver form factors: SFP, SFP+, SFP28, QSFP+, QSFP28, QSFP-DD, CFP2, XFP, and CXP with speeds and distances.
WiFi Standards (IEEE 802.11)
Reference table of WiFi standards: 802.11b through 802.11be (Wi-Fi 1 to Wi-Fi 7) with maximum speeds, frequencies, and release years.
Power Connectors & Receptacles
Reference table of data center power connectors: NEMA 5-15P, L6-30P, IEC C13/C14, C19/C20, IEC 60309, Schuko, and BS 1363 with amp and voltage ratings.
Device Naming Conventions
Standard network device naming convention: use a <site>-<role>-<number> pattern. See examples for switches, firewalls, servers, and stack members.
Interface & Port Naming
How to standardize network interface names across vendors: Cisco IOS, Juniper Junos, and NX-OS/AOS-CX conventions with examples.
VLAN & Subnet Naming
Best practices for VLAN naming: descriptive names like SRV-PROD and GUEST-WIFI paired with documented VLAN IDs and subnets.