6
votes
3answers
74 views

How does one capture traffic on virtual interfaces?

I would like to capture traffic on Linux virtual interfaces, for debugging purposes. I have been experimenting with veth, tun and dummy interface types; on all three, I am having trouble getting ...
2
votes
1answer
31 views

tcpdump command works only on local ip

I am trying to capture some IP packets in my personal LAN with tcpdump, through the command tcpdump -A -i eth0 'tcp and (((ip[2:2] - ((ip[0]&0xf)<<2)) - ((tcp[12]&0xf0)>>2)) != 0) ...
1
vote
1answer
35 views

Network issue - only one machine can't access webpage on another machine

I'm trying to figure out why my MacBook is unable to reach the web page served by my Raspberry Pi while other computers on my local network (or on external networks) have no problems seeing the web ...
0
votes
2answers
615 views

tcp dump outgoing connection packets

What is the command syntax to log all tcp connection packets? I am trying to see what address and ports my computer is trying to connect to outgoing so that I may config my firewall.
1
vote
0answers
313 views

Packets not received by TUN device

I created a TUN device(nat64) and created a route so that all the required packets are forwarded to the TUN device from an eth device. But, I see that many packets are not received by the TUN device. ...
1
vote
1answer
526 views

tcpdump and https

Why following command doesnt grab the packets to faceebook site sudo tcpdump host facebook.com and dst port 443 but next grabs sudo tcpdump host java.com
2
votes
1answer
1k views

iptrace for linux: how can I trace full packet contents?

I normally use iptrace on our AIX servers to get packet traces but have recently found out that this doesn't work for other 'nix systems - namely Centos. Does anyone know what the analog would be? ...
8
votes
1answer
861 views

what level of the network stack does tcpdump get its info from?

As I was trying in vain to fix a faulty ethernet controller here, one thing I tried was running tcpdump on the machine. I found it interesting that tcpdump was able to detect that some of the ICMP ...
7
votes
1answer
4k views

Buffer size for capturing packets in kernel space?

Going through the man page of tcpdump, it seems kernel can drop the packets if the buffer is full. I was wondering if: that size is configurable and/or where can I see the size for my distro? From ...
2
votes
1answer
821 views

Is it possible to capture all network traffic using tcpdump?

I have 3 computers on the same sub-net. Computer A and B are communicating with each other (ping, telnet, etc.). I'd like to see the packets between A and B on computer C. Is it possible to do this ...
0
votes
2answers
696 views

Understanding tcpdump output on a linux router

My router has an atm0 interface and a VLAN (atm0.1) interface, atm0.1 has the WAN IP address. When using tcpdump -i atm0, the packets captured are only outgoing packet (LAN to WAN). 05:34:19.504895 ...