How to retrieve both TCP and UDP ports with Nmap? [closed]

Answer 1

As you've seen, UDP scanning is slow as open/filtered ports typically don't respond so nmap has to time out and then retransmit whilst closed ports will send a ICMP port unreachable error, which systems typically rate limit.

You can add the -T switch to increase the speed of the scan, though this may reduce accuracy and make it easier to detect.

-T<0-5>: Set timing template (higher is faster)

-PN will turn off the ping scan element

You could also scan more hosts in parallel,

or reduce the number of ports you're scanning with the -p switch or --top-ports , which will scan the highest-ratio ports found in the nmap-services file.

If you were scanning multiple hosts, you could use --host-timeout to skip slow hosts.

Regarding TCP, -sS should be quicker than -sT.

HTH!

Answer 2

You didn't say how slow your scans get, but I think you would benefit from playing with the --min-parallelism option, which adjusts the minimum number of outstanding probes.

I'm seeing 70% reductions in scan time (compared with bare -sT -sU scans) like this. Note that it is possible to set --min-parallelism too high, such that the host (or network) cannot buffer this many queries simultaneously.

[mpenning@Hotcoffee]$ sudo nmap --min-parallelism 100 -sT -sU localhost

Starting Nmap 5.00 ( http://nmap.org ) at 2012-05-10 01:07 CDT
Interesting ports on localhost (127.0.0.1):
Not shown: 1978 closed ports
PORT     STATE         SERVICE
22/tcp   open          ssh
25/tcp   open          smtp
49/tcp   open          tacacs
53/tcp   open          domain
80/tcp   open          http
111/tcp  open          rpcbind
631/tcp  open          ipp
2003/tcp open          finger
2004/tcp open          mailbox
3389/tcp open          ms-term-serv
5901/tcp open          vnc-1
5910/tcp open          unknown
6001/tcp open          X11:1
7002/tcp open          afs3-prserver
53/udp   open|filtered domain
69/udp   open|filtered tftp
111/udp  open|filtered rpcbind
123/udp  open|filtered ntp
161/udp  open|filtered snmp
631/udp  open|filtered ipp
1812/udp open|filtered radius
1813/udp open|filtered radacct

Nmap done: 1 IP address (1 host up) scanned in 1.54 seconds
[mpenning@Hotcoffee]$