Arch Linux

graysky

Wiki Maintainer

From: :wq

Registered: 2008-12-01

Posts: 10,691

Website

Recently, nmap fails to return hosts on my network

Recently, I am unable to use nmap to scan my LAN.

# nmap -sP 192.168.1.0/24 

Starting Nmap 7.40 ( https://nmap.org ) at 2017-06-11 10:20 EDT
Nmap done: 256 IP addresses (0 hosts up) scanned in 206.27 seconds

In the past, this would have listed out all the nodes on the network.  I have DHCP configured for the onboard NIC via systemd-networkd.  When I boot from the liveCD I get the expected results so I believe I have something misconfigured...

EDIT: should have included:

% cat /etc/systemd/network/wired.network 
[Match]
Name=enp2s0

[Network]
DHCP=both

Last edited by graysky (2017-06-11 14:40:10)

---

CPU-optimized Linux-ck packages @ Repo-ck  • AUR packages • Zsh and other configs

fsckd

Forum Fellow

Registered: 2009-06-15

Posts: 4,173

Re: Recently, nmap fails to return hosts on my network

Can you ping or otherwise communicate with other hosts?

---

aur S & M :: forum rules :: Community Ethos
Resources for Women, POC, LGBT*, and allies

graysky

Wiki Maintainer

From: :wq

Registered: 2008-12-01

Posts: 10,691

Website

Re: Recently, nmap fails to return hosts on my network

Yes, it is just the nmap command that fails.

---

CPU-optimized Linux-ck packages @ Repo-ck  • AUR packages • Zsh and other configs

x33a

Forum Fellow

Registered: 2009-08-15

Posts: 4,587

Re: Recently, nmap fails to return hosts on my network

Try -sn instead of -sP.

ewaller

Administrator

From: Pasadena, CA

Registered: 2009-07-13

Posts: 20,348

Re: Recently, nmap fails to return hosts on my network

Sorry Graysky

ewaller@turing ~ 1002 %nmap -sP 192.168.1.0/24

Starting Nmap 7.50 ( https://nmap.org ) at 2017-06-25 08:12 PDT
Nmap scan report for router.home (192.168.1.1)
Host is up (0.0029s latency).
Nmap scan report for turing (192.168.1.2)
Host is up (0.00013s latency).
Nmap scan report for 192.168.1.5
Host is up (0.047s latency).
Nmap scan report for HP256D03 (192.168.1.17)
Host is up (0.046s latency).
Nmap scan report for alarmpi (192.168.1.48)
Host is up (0.0052s latency).
Nmap scan report for android-aec8d7a11c73e2fb (192.168.1.126)
Host is up (0.0028s latency).
Nmap scan report for 192.168.1.133
Host is up (0.055s latency).
Nmap scan report for android-5e2e62661a3ccbc2 (192.168.1.136)
Host is up (0.061s latency).
Nmap done: 256 IP addresses (8 hosts up) scanned in 8.38 seconds
ewaller@turing ~ 1003 %

---

Nothing is too wonderful to be true, if it be consistent with the laws of nature -- Michael Faraday
Sometimes it is the people no one can imagine anything of who do the things no one can imagine. -- Alan Turing
---
How to Ask Questions the Smart Way

graysky

Wiki Maintainer

From: :wq

Registered: 2008-12-01

Posts: 10,691

Website

Re: Recently, nmap fails to return hosts on my network

Try -sn instead of -sP.

I get the same result using -sn as I did with -Sp:

% sudo nmap -sn 10.8.10.0/24

Starting Nmap 7.50 ( https://nmap.org ) at 2017-06-25 11:09 EDT
Nmap done: 256 IP addresses (0 hosts up) scanned in 206.27 seconds

---

CPU-optimized Linux-ck packages @ Repo-ck  • AUR packages • Zsh and other configs

ewaller

Administrator

From: Pasadena, CA

Registered: 2009-07-13

Posts: 20,348

Re: Recently, nmap fails to return hosts on my network

As a sanity check ,what are the output of ip addr
?

Edit:  Are you trying to fight namp at the same time you are fighting your VPN configuration issues on your other thread?  Mayhaps you are trying to scan through a VPN rather than locally.

Last edited by ewaller (2017-06-25 15:19:24)

---

Nothing is too wonderful to be true, if it be consistent with the laws of nature -- Michael Faraday
Sometimes it is the people no one can imagine anything of who do the things no one can imagine. -- Alan Turing
---
How to Ask Questions the Smart Way

graysky

Wiki Maintainer

From: :wq

Registered: 2008-12-01

Posts: 10,691

Website

Re: Recently, nmap fails to return hosts on my network

@wealler - No, this issue is 100% unrelated to my other thread.

The answer to your question:

: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel master br0 state UP group default qlen 1000
    link/ether 43:1a:5b:9e:e7:a1 brd ff:ff:ff:ff:ff:ff
3: br0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether e2:10:11:be:6d:b2 brd ff:ff:ff:ff:ff:ff
    inet 10.8.10.101/24 brd 10.8.10.255 scope global dynamic br0
       valid_lft 69308sec preferred_lft 69308sec
    inet6 fe80::e010:11ff:febe:7db6/64 scope link 
       valid_lft forever preferred_lft forever

Last edited by graysky (2017-06-25 15:40:23)

---

CPU-optimized Linux-ck packages @ Repo-ck  • AUR packages • Zsh and other configs

ewaller

Administrator

From: Pasadena, CA

Registered: 2009-07-13

Posts: 20,348

Re: Recently, nmap fails to return hosts on my network

I am afraid you are as sane as I am

Edit:   .... but I note that your 10.0.10.x/24 network is on br0.  Where does that bridge go?

Last edited by ewaller (2017-06-25 16:08:51)

---

Nothing is too wonderful to be true, if it be consistent with the laws of nature -- Michael Faraday
Sometimes it is the people no one can imagine anything of who do the things no one can imagine. -- Alan Turing
---
How to Ask Questions the Smart Way

seth

Member

Registered: 2012-09-03

Posts: 61,251

Re: Recently, nmap fails to return hosts on my network

nmap -sP -e br0 10.8.10.0/24

Hey, it's totally unfair to edit your post while i'm reading the rest of the thread ;-P

Last edited by seth (2017-06-25 16:17:45)

---

How to upload text · How to boot w/o GUI · Disable Windows Fast-Start! · Fix your xinitrc