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Transport Layer (Layer 4) - Reserved TCP and UDP Port Numbers
| Port | Keyword | Description |
| 0 | - | Reserved |
| 1-4 | - | Unassigned |
| 5 | rje | Remote job entry |
| 7 | echo | Echo |
| 9 | discard | Discard |
| 11 | users | Active users |
| 13 | daytime | Day |
| 15 | netstat | Who is up or netstat |
| 17 | quote | Quote of the day |
| 19 | chargen | Character generator |
| 20 | ftp-data | File Transfer Protocol (data) |
| 21 | ftp | File Transfer Protocol |
| 23 | telnet | Terminal connection |
| 25 | smtp | Simple Mail Transfer Protocol |
| 37 | time | Time of day |
| 39 | rlp | Resource Location Protocol |
| 42 | nameserver | Hostname server |
| 43 | nickname | WhoIs |
| 53 | domain | Domain Name Server |
| 67 | bootps | Bootstrap protocol server |
| 68 | bootpc | Bootstrap protocol client |
| 69 | tftp | Trivial File Transfer Protocol |
| 75 | - | Any private dial-out service |
| 77 | - | Any private RJE service |
| 79 | finger | Finger |
| 80 | http | Hypertext Transfer Protocol |
| 123 | ntp | Network time protocol |
| 133-159 | - | Unassigned |
| 160-223 | - | Reserved |
| 224-241 | - | Unassigned |
| 242-255 | - | Unassigned |
You must be familiar with these Transport Layer (4) Port assignments. For a complete list -- check out this superb site HERE. Also -- it would be a smart thing to memorize this list:
-
0 to 254 - used for public applications.
-
255 to 1023 - assigned to companies* for marketable applications.
-
1024 and above - unregulated.
* Real Audio's rtsp (real-time streaming protocol) via port 554 is a good example.
Don't forget -- no matter what you may discover out
there in cyberspace regarding transport layer ports -- focus on how they are
assigned within Cisco's world of internetworking.