I'm trying to run tcpdump on linux machine, which needs to write pcap on the remote server with file rotation every 10 seconds.
tcpdump -s0 -i eth0 -G 10 -w - | ssh {remote_ip} "cat > capture_%d-%m_%Y__%H_%M.pcap"
The file gets return on the remote server for first cycle (10 seconds) and then I'm getting the following error.
tcpdump: listening on ens224, link-type EN10MB (Ethernet), capture size 262144 bytes
tcpdump: Can't write to standard output: Bad file descriptor
I'm using -G for time based rotation, if I remove -G, then i'm able to write to remote server continuously.
My remote server is configured with password-less login form this host.
You can pipe tcpdump to another tcpdump so in your case :
tcpdump -i eth0 -w - not port 22 | \
ssh my.remote.host tcpdump -r - -w /tmp/capture_%d-%m_%Y__%H_%M_%S.pcap -G 2 -C 100
Related
I am trying to capture the DHCP frames for analysis using the following command in my mac book.
sudo tshark -i en0 -f "port 67 or port 68" -a duration:300 -w /tmp/dump.pcap
I use the following command to get all the fields of all protocols in the packet but it is not printing any value. Is the capture filter option for the DHCP frame is correct? Any help is appreciated?
sudo tshark -T text -r /tmp/dump.pcap -V
Answer
Yes, your commands are OK. Maybe no DHCP packets arrived and therefore not captured. Try to force a DHCP activity by commands in second teminal window of the same device:
sudo dhclient -r
sudo dhclient
Warning: Do not apply these commands if you are connected remotely. First command releases the IP address and your connection will be interrupted without a possibility to put second command and get address back remotely.
Some details concerning data capture
The thsark filters have the same syntax as Wireshark.
Threre exist 2 (or 3) filter types:
capture filter, -f tshark option: It selects which packets will be captured and which not. This is useful e.g. for getting lower capture file size.
display filter, -Y tshark option: It selects which packets will be displayed from all captured ones.
You can combine both types.
Examples:
tshark -i eth0 -n -Y "ip.addr==8.8.8.8"
tshark -i eth0 -n -Y "ip.addr==8.8.8.8" -f "udp port 53"
tshark -i eth0 -n -Y "ip.addr==8.8.8.8 and udp.port==53"
All packets are captured, but only the 8.8.8.8 IP address packets are displayed.
Only the DNS packets are captured, and only the 8.8.8.8 IP address packets from captured are displayed.
All packets are captured, but only the 8.8.8.8 IP address packets having UDP port 53 (i.e. DNS) are displayed. Compare different syntax of the port filtering between the display and the capture filters in line above.
All other options like -a, -b, -w, -s can be applied too.
The tcpdump application is usefull too. It is available in most Linux systems even very small or special. It does not have a display filter option. Only capture filters can be applied. Other options are missing: -a, -b ...
sudo tcpdump -i eth0 -w /tmp/dhcp.pcap "udp port 67 or udp port 68"
Hello guys i need to resolve this problem (all server have installed centos 7): i'm trying to create a gre tunnel through vps (in Italy - OpenVZ) and a dedicated server (in Germany), but they do not communicate internally (ping and ssh command tests). Next i create a gre tunnel trought vps (in Italy - OpenVZ) and vps (in France - KVM OpenStack) and their communicate, i next i had create a tunnel trought vps (in France - KVM OpenStack) and a dedicated server (in Germany) their communicate. I can not understand why the vps (in Italy - OpenVZ) and the dedicated server (in Germany) do not communicate, ideas on how I can fix (
I also tried with iptables disabled, firewalld is not enable)? Thanks
In other words:
In other attempts (by this i mean that i managed to successfully create the GRE Tunnel between these machines):
The VPS (in France) and VPS (in Italy) communicate internally (ping and ssh command tests)
The VPS (in France) and Dedicated Server (in Germany) communicate internally (ping and ssh command tests)
Problem (by this i mean that i could not successfully create the GRE Tunnel between these machines):
The VPS (in Italy) and Dedicated Server (in Germany) do not communicate internally (ping and ssh command tests). I also asked hosting services if they had any restrinzione but nothing.
My configuration:
VPS command for tunnel:
echo 'net.ipv4.ip_forward=1' >> /etc/sysctl.conf
iptunnel add gre1 mode gre local VPS_IP remote DEDICATED_SERVER_IP ttl 255
ip addr add 192.168.168.1/30 dev gre1 ip link set gre1 up
Dedicated server command for tunnel:
iptunnel add gre1 mode gre local DEDICATED_SERVER_IP remote VPS_IP ttl 255
ip addr add 192.168.168.2/30 dev gre1
ip link set gre1 up
[root#VPS ~]# ping 192.168.168.2
PING 192.168.168.2 (192.168.168.2) 56(84) bytes of data.
^C
--- 192.168.168.2 ping statistics ---
89 packets transmitted, 0 received, 100% packet loss, time 87999ms
[root#DE ~]# ping 192.168.168.1
PING 192.168.168.1 (192.168.168.1) 56(84) bytes of data.
^C
--- 192.168.168.1 ping statistics ---
92 packets transmitted, 0 received, 100% packet loss, time 91001ms
[root#VPS ~]# tcpdump -i venet0 "proto gre" tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on venet0, link-type LINUX_SLL (Linux cooked), capture size 262144 bytes ^C 0 packets captured 1 packet received by filter 0 packets dropped by kernel
[root#DE ~]# tcpdump -i enp2s0 "proto gre" tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on enp2s0, link-type EN10MB (Ethernet), capture size 262144 bytes ^C 0 packets captured 0 packets received by filter 0 packets dropped by kernel
[root#VPS ~]# lsmod | grep gre
ip_gre 4242 -2
ip_tunnel 4242 -2 sit,ip_gre
gre 4242 -2 ip_gre
[root#DE ~]# lsmod | grep gre
ip_gre 22707 0
ip_tunnel 25163 1 ip_gre
gre 13144 1 ip_gre
Console image with full command output
If ip_forwarding is required for the tunnel to work, you need to do /sbin/sysctl -p
And what does the output of ip tunnel show and ip route show on both the ends
I am capturing network traffic by using tcpdump. The problem is: I can't see all capture data when the package is too long. For example, when the tcp frame length is more than 500, I just see 100-200 or less. How to display all frame data(500+)?
I have tried add -vv and -vvv parameter. This is my current command:
tcpdump -i eth1 tcp and host 10.27.13.14 and port 6973 -vv -X -c 1000
Add -s0 parameter:
tcpdump -i eth1 tcp and host 10.27.13.14 and port 6973 -s0 -vv -X -c 1000
I am running the following command in my server(GNU/LINUX 2.6.27.5):
tcpdump -i eth0 -w test.pcap
After stopping the packet capture manually it shows the number of packets captured & received by filter but the file test.pcap does not contain anything, means its size is 0.
tcpdump version used is tcpdump-3.9.8
I have been using wire-shark to analyse the packets of socket programs, Now i want to see the traffic of other hosts traffic, as i found that i need to use monitor mode that is only supported in Linux platform, so i tried but i couldn't capture any packets that is transferred in my network, listing as 0 packets captured.
Scenario:
I'm having a network consisting of 50+ hosts (all are powered by windows Except mine), my IP address is 192.168.1.10, when i initiate a communication between any 192.168.1.xx it showing the captured traffic.
But my requirement is to monitor the traffic of 192.168.1.21 b/w 192.168.1.22 from my host i,e. from 192.168.1.10.
1: is it possible to capture the traffic as i mentioned?
2: If it is possible then is wire-shark is right tool for it (or should i have to use differnt one)?
3: if it is not possible, then why?
Just adapt this a bit with your own filters and ips : (on local host)
ssh -l root <REMOTE HOST> tshark -w - not tcp port 22 | wireshark -k -i -
or using bash :
wireshark -k -i <(ssh -l root <REMOTE HOST> tshark -w - not tcp port 22)
You can use tcpdump instead of tshark if needed :
ssh -l root <REMOTE HOST> tcpdump -U -s0 -w - -i eth0 'port 22' |
wireshark -k -i -
You are connected to a switch which is "switching" traffic. It bases the traffic you see on your mac address. It will NOT send you traffic that is not destined to your mac address. If you want to monitor all the traffic you need to configure your switch to use a "port mirror" and plug your sniffer into that port. There is no software that you can install on your machine that will circumvent the way network switching works.
http://en.wikipedia.org/wiki/Port_mirroring