Reference · 3 min read
The ports every network engineer should know cold
Mid-incident is the wrong time to look up a port number. A handful come up constantly in firewall rules, ACLs and packet captures - knowing them on sight tells you the protocol and whether it belongs there.
The must-knows
- →22 SSH, 23 Telnet (avoid), 53 DNS
- →80 HTTP, 443 HTTPS
- →179 BGP, 500 / 4500 IKE and IPsec NAT-T
- →161 / 162 SNMP, 514 Syslog, 123 NTP
- →1812 / 1813 RADIUS, 636 LDAPS
Why memorize them
When a rule or a capture flies past during an outage, recognizing the port instantly is the difference between reading the flow and stopping to search. It also catches mistakes fast - BGP on anything but 179, or Telnet where SSH should be, jumps out.
Common port reference
Search well-known TCP/UDP ports by number or service.
Practise this on today’s Daily Ops Drill — a free network task every day.
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