~/netref / Print Cheatsheet
##
Print / Export Cheatsheet
A compact, ink-friendly one-pager with the essential tables. Hit print and choose “Save as PDF”.
// CIDR — mask · wildcard · hosts
| CIDR | Mask | Hosts |
|---|---|---|
| /0 | 0.0.0.0 | 4,294,967,294 |
| /1 | 128.0.0.0 | 2,147,483,646 |
| /2 | 192.0.0.0 | 1,073,741,822 |
| /3 | 224.0.0.0 | 536,870,910 |
| /4 | 240.0.0.0 | 268,435,454 |
| /5 | 248.0.0.0 | 134,217,726 |
| /6 | 252.0.0.0 | 67,108,862 |
| /7 | 254.0.0.0 | 33,554,430 |
| /8 | 255.0.0.0 | 16,777,214 |
| /9 | 255.128.0.0 | 8,388,606 |
| /10 | 255.192.0.0 | 4,194,302 |
| /11 | 255.224.0.0 | 2,097,150 |
| /12 | 255.240.0.0 | 1,048,574 |
| /13 | 255.248.0.0 | 524,286 |
| /14 | 255.252.0.0 | 262,142 |
| /15 | 255.254.0.0 | 131,070 |
| /16 | 255.255.0.0 | 65,534 |
| /17 | 255.255.128.0 | 32,766 |
| /18 | 255.255.192.0 | 16,382 |
| /19 | 255.255.224.0 | 8,190 |
| /20 | 255.255.240.0 | 4,094 |
| /21 | 255.255.248.0 | 2,046 |
| /22 | 255.255.252.0 | 1,022 |
| /23 | 255.255.254.0 | 510 |
| /24 | 255.255.255.0 | 254 |
| /25 | 255.255.255.128 | 126 |
| /26 | 255.255.255.192 | 62 |
| /27 | 255.255.255.224 | 30 |
| /28 | 255.255.255.240 | 14 |
| /29 | 255.255.255.248 | 6 |
| /30 | 255.255.255.252 | 2 |
| /31 | 255.255.255.254 | 2 † |
| /32 | 255.255.255.255 | 1 † |
// mask octet quick map
| Bits | Octet | Wild | Block |
|---|---|---|---|
| /0 | 0 | 255 | 256 |
| /1 | 128 | 127 | 128 |
| /2 | 192 | 63 | 64 |
| /3 | 224 | 31 | 32 |
| /4 | 240 | 15 | 16 |
| /5 | 248 | 7 | 8 |
| /6 | 252 | 3 | 4 |
| /7 | 254 | 1 | 2 |
| /8 | 255 | 0 | 1 |
// OSI model
| # | Layer | PDU |
|---|---|---|
| 7 | Application | Data |
| 6 | Presentation | Data |
| 5 | Session | Data |
| 4 | Transport | Segment |
| 3 | Network | Packet |
| 2 | Data Link | Frame |
| 1 | Physical | Bit |
// administrative distance
| Connected interface | 0 |
| Static route | 1 |
| EIGRP summary | 5 |
| External BGP | 20 |
| Internal EIGRP | 90 |
| OSPF | 110 |
| IS-IS | 115 |
| RIP | 120 |
| Internal BGP | 200 |
| Unreachable | 255 |
// private & reserved
| 10.0.0.0/8 | Private (RFC 1918) — Class A |
| 172.16.0.0/12 | Private (RFC 1918) — 172.16–172.31 |
| 192.168.0.0/16 | Private (RFC 1918) — Class C |
| 127.0.0.0/8 | Loopback |
| 169.254.0.0/16 | Link-local / APIPA |
| 100.64.0.0/10 | Carrier-grade NAT (RFC 6598) |
| 0.0.0.0/8 | "This" network / unspecified |
| 192.0.2.0/24 | Documentation TEST-NET-1 |
| 198.51.100.0/24 | Documentation TEST-NET-2 |
| 203.0.113.0/24 | Documentation TEST-NET-3 |
| 224.0.0.0/4 | Multicast (Class D) |
| 240.0.0.0/4 | Reserved (Class E) |
| 255.255.255.255/32 | Limited broadcast |
// well-known ports
| 20/21 | FTP (data / control) | TCP |
| 22 | SSH / SCP / SFTP | TCP |
| 23 | Telnet | TCP |
| 25 | SMTP | TCP |
| 49 | TACACS+ | TCP/UDP |
| 53 | DNS | UDP/TCP |
| 67/68 | DHCP (server / client) | UDP |
| 69 | TFTP | UDP |
| 80 | HTTP | TCP |
| 88 | Kerberos | TCP/UDP |
| 110 | POP3 | TCP |
| 119 | NNTP | TCP |
| 123 | NTP | UDP |
| 137/139 | NetBIOS | TCP/UDP |
| 143 | IMAP | TCP |
| 161/162 | SNMP (agent / trap) | UDP |
| 179 | BGP | TCP |
| 389 | LDAP | TCP/UDP |
| 443 | HTTPS / TLS | TCP |
| 445 | SMB / CIFS | TCP |
| 465/587 | SMTP over TLS | TCP |
| 500 | IKE / IPsec | UDP |
| 514 | Syslog | UDP |
| 520 | RIP | UDP |
| 546/547 | DHCPv6 | UDP |
| 636 | LDAPS | TCP |
| 646 | MPLS LDP | TCP/UDP |
| 853 | DNS over TLS | TCP |
| 990 | FTPS | TCP |
| 993 | IMAPS | TCP |
| 995 | POP3S | TCP |
| 1194 | OpenVPN | UDP |
| 1433 | MS SQL Server | TCP |
| 1701 | L2TP | UDP |
| 1723 | PPTP | TCP |
| 1812/1813 | RADIUS (auth / acct) | UDP |
| 2049 | NFS | TCP/UDP |
| 3260 | iSCSI | TCP |
| 3306 | MySQL / MariaDB | TCP |
| 3389 | RDP | TCP |
| 4500 | IPsec NAT-T | UDP |
| 5060/5061 | SIP | UDP/TCP |
| 5432 | PostgreSQL | TCP |
| 5900 | VNC | TCP |
| 5985/5986 | WinRM | TCP |
| 6379 | Redis | TCP |
| 8080 | HTTP alt / proxy | TCP |
| 8443 | HTTPS alt | TCP |
| 27017 | MongoDB | TCP |