NMAP syn scan - half-open scan - just send a syn packet

nmap -T4 -v -PN -n -sS --top-ports 100 --maxparallelism 10 -oA nmapSYN IP

T - speed
v - verbose
PN - not to ping or identity
-n - no dns resolution

sS - syn packet scan

--top-ports 100

--max-parallelism 10

-oA - output

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nmap -T4 -v -PN -n -sA --top-ports 100 --maxparallelism 10 -oA nmapSYN IP

-sA - it never determins open ports

it is uses to map firewall ports -

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aggressive option

nmap -T5 -PN -v -A -oA nmapcomplete IP