With 67 and 68 you also often want 69 there, the Trivial FTP content to boot strap (and don't forget 4011 if you're going full on PXE boot!). See also pairs of

With 67 and 68 you also often want 69 there, the Trivial FTP content to boot strap (and don't forget 4011 if you're going full on PXE boot!). See also pairs of channels as in 20 FTP data, 21 FTP control, or SNMP 161 and 162, or versions of channels such as 109 POP2 and 110 POP3. Or greedy designs, like NetBIOS with 137, 138, and 139, which folks later realized could be done on a single port like 445. :-)