Packet capture is the act of capturing data packets crossing a computer network. Packet capture can be: Deep packet capture (headers & payload), or partial packet capture (headers only).

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Using I/O graph how to interept bytes/tick against packet details information?

I'm working on a trace-file which has reported ISP throttling occurrences in it. My task is to use IO graph to understand at what point in time the throttling process effected client upload ...
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15 views

iptables — capture pptp connection attempt packets and place into holding pattern

Problem I have a problem of too many simultaneous connection attempts to a vpn server causing all connections to drop. Staggering connection attempts fixes problem. How can I use iptables to do the ...
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1answer
26 views

tcpdump freezes and not capturing properly without internet connection

When I don't have any internet conncetion and I want to capture network between local computers, tcpdump acts like this: 1.I start tcpdump using following command: tcpdump -ixenbr0 2.After I run ...
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1answer
53 views

How to ping a host with different MTU size to simulate icmpv6 packet too big scenario?

As the Title states,I want to check whether my host will actually send a ICMPv6 packet too big if i send a packet with beyond the defined MTU size.I don't have a cisco router(extended ping) to try out ...
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1answer
86 views

server is not responding on SYN packets

On the attached tcp dump, the first two SYN packets (#21800 and 21801) came to the server, however SYN ACK was sent for the second SYN. Is that correct behaviour? My understanding is that the client ...
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1answer
96 views

Suspicious IP packets on port 53

I have discovered a strange issue, and I hope someone can help me to fix it. If I'm capturing the ip packets on em1 network interface on port 53 with the "tcpdump -i em1 -vvv -s 0 -l -n port 53" ...
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1answer
266 views

user agent in http or https request

Is there any way that I can differentiate, the HTTP or HTTPS packets are coming from browser or not ? specially for https request.There is User-Agent field in packet in Http,but I could not found ...
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72 views

Redirect Default Gateway Traffic in Linux to File

I am trying to troubleshoot one of my linux servers (ubuntu server). Therefore I want to intercept all traffic that is sent to the default gateway and then write it to a file: preferably some kind of ...
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1answer
92 views

Is it Possible to Capture All HTTP Packets to a Target IP on a subnet?

I've been trying to use tcpdump to capture packets to a target IP on my subnet, but am unable to do so successfully. I've tried: tcpdump -i eth0 net network-ip-address/27 -A and tcp port 80 But it ...
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60 views

Early tear down of communication

I have an application which performs an LDAP search which works in one domain but not in the other, when analyzing the packets sent between the application server and the domain controller being ...
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1answer
99 views

Analyzing twitter packets [closed]

Thanks for your time. I'd like to find a way if a client has made a 'GET' or a 'POST' request for twitter. We are currently doing an educational project and we wanted to understand how we can achieve ...
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1answer
207 views

Why is my chunked request removing the trailing CRLF?

I've just spent the past 10 hours trying to figure out why my http request was failing when I did a request.Content.ReadAsMultipartAsync().Result.Contents It kept returning the error: Unexpected ...
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1answer
65 views

How many data packets does it take to log in to facebook? [closed]

I want to find out how many packets are sent when visiting a site on the web. What's a good program that would help me get this kind of data?
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1answer
362 views

Tcpdump on ec2 not seeing all packets

I'm running tcpdump on an Amazon EC2 instance to monitor HTTP traffic going to Nginx (this is just a test box, the only resource is the example test page). Running tcpdump with the command # ...
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1answer
236 views

Compressing the output of tshark when in multiple files mode

I'm running tshark to dump wireless traffic. I am currently running in multiple files mode, splitting output into 50MB chunks. Is there any way to also have these 50MB chunks compressed with something ...
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1answer
1k views

Linux NFLOG - documentation, configuration from C

Several different places (e.g. http://wiki.wireshark.org/CaptureSetup/NFLOG) recommend using Linux's "NFLOG" firewall module to capture packets generated by a particular UID, like this: # iptables -A ...
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1answer
282 views

iperf udp sequence number wireshark

I'm using iperf for generating udp traffic and my objective is to measure paquet loss. I wanted to know if the first 4 Bytes of Iperf Data are currently the sequence number.
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2answers
630 views

block all packets in windows 7 (so nothing appears in wireshark)? Can anything locally installed do it?

is it possible to block all packets in windows 7, so that nothing appears in wireshark? I have tried choosing Block all for incoming. for outgoing, I see it has no block all option, just a block ...
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1answer
1k views

TCP Sequence & Acknowledgment numbers

I have looked through other questions on here involving the relevant topics, but I am still not clear on this. I have just been reading this explanation of TCP sequence & acknowledgment numbers. ...
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1answer
194 views

Wireshark seems to ignore my filters

I'm trying to make use of Wireshark 1.10.6 for Windows and I want to only capture the traffic to port 443 (to diagnose some weird HTTPS problems I'm having). So I open Capture -> Capture Filters... ...
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2answers
341 views

Can I capture ISP SNMP information with Wireshark?

I am trying to do some heavy digging into SNMP, BPI+, ISP networks. Since wireshark can be used to capture network data, would I be able to use it to remotely capture my ISP SNMP agent information and ...
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2answers
848 views

How can I create a packet capture file on a headless server for a single process?

I'm writing a python script on a headless server, and I'd like to see the packet capture output for the script. I can't run ettercap or Wireshark on the server as there is too much other noise ...
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1answer
430 views

Strange Ethernet II packets in wireshark

Looking at a wireshark capture, I'm seeing something really strange. Ethernet II packets with random data are being sent on the network. The larger packets in the capture seem to contain bits and ...
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132 views

Suggestions on how to capture network connections/traffic for determining browser/SSL versions?

Note that I posted this Q to the StackExchange InfoSec site, but its not as populated as ServerFault and this is more on the technical side of network collection for web services. I've started ...
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2answers
163 views

Linux Full Packet Capture

I’m looking to stand up a full packet capture solution on an Ubuntu server. Our maximum bandwidth is < 60Mb/s and the server has 10K hard drives. Ideally, I’d like to be able to log everything ...
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1answer
2k views

Why is the “don't fragment” flag set in https and ssh protocols?

I've found a lot of information specifying that this is the case, however, I am really looking for the reason behind this. Why is it necessary? Is it necessary?
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137 views

Network card capable of capturing a tonne of packets and not dropping them?

Edit: Our server is trying to capture packets at between 500-600Mb/s, but is dropping packets 'due to kernel'. Data is being written to SSDs, and isn't bottleneck there. What things should I look ...
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1answer
297 views

“tshark: There are no interfaces on which a capture can be done” in Amazon Linux AMI

My goal is to capture packets with tshark in Amazon Linux AMI. While typing tshark in the command line there's an error: "tshark: There are no interfaces on which a capture can be done" How to ...
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1answer
285 views

tcpdump on a capture card

I have a server with a NT20E Capture Card (2x10Gb Packet Capture Card over PCI Express). I want to be able to dump the output to a pcap format but because this isn't listed as an ethX-interface ...
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3answers
2k views

How to sniff all HTTP packets on a wifi network? [closed]

I need to sniff all HTTP packets that pass through my wifi network (in particular HTTP requests by my smartphone). I've tried with wireshark, but I can sniff only packets to and from my pc. What am I ...
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3answers
4k views

Can Wireshark capture an entire Ethernet frame including preamble, CRC and Interframe spacing?

I am examining an Ethernet frame in Wireshark. According to the "Ethernet frame" Wikipedia article and accompanying diagrams, "A frame starts with a 7-octet preamble and 1-octet start frame delimiter ...
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1answer
473 views

Incoming Outgoing Packets Wireshark

Is there a way to have a column or a filter that marks each packet as incoming (download) or outgoing (upload) in Wireshark? I guess this should be relative to the selected capture interface device.
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387 views

Source and Destination Packets on Wireshark Relative or Absolute?

New in Packet Analysis. Sniffing on the Ethernet device of my computer. Does the Source and Destination columns on Wireshark tell the source and destination from where the packet was originated and ...
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496 views

What does a packet capture in pfsense do?

I have some issues with a third party to establish a VPN connection. To debug it, I made a packet capture on the device that represents our synchronous DSL line. The solution I'm using is an old ...
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1answer
109 views

Meraki VPN Traffic Capture

We have multiple offices interconnected via VPN using Meraki switches. I've been looking around and can't seem to find a way, but was thinking it's possible. Is it possible for me to put my desktop on ...
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2answers
368 views

monitor network packet rate per IP

my problem is that I've got a report that my IP was used in a DOS attack. Problem is that I do not know which computer is infected and the attack is not active anymore. Is there simple Linux tool for ...
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1answer
516 views

syn flood attack — packet hits on shared ip

How can I dump the TCP packets to get a better idea to know which website is being attacked? Here is what I have in my logs: May 4 23:10:26 host kernel: [2130002.635000] Firewall: *SYNFLOOD ...
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6answers
601 views

Wireshark Capture Between Two Routers

How would one go about capturing OSPF traffic in Wireshark between two routers? I'm looking to do something like this: [RTR A] - - - [LAPTOP] - - - [RTR B]
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1answer
104 views

Wireshark not displaying GET or POST data [closed]

I'm a student and I'm taking my first networking class. I'm working on an assignment designed to get me used to using Wireshark and understanding packet transfers. Part of the assignment is to collect ...
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2answers
340 views

What are cables/boxes called for listening in on a RJ45 cable?

I would like to capture the traffic from a router, so I assume there must exist a cable or hardware box with 3 RJ45 socks, where two of them are IN and OUT, and the third is for capturing device (a ...
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2answers
1k views

Method to drop 50% packets of the total

On my machine I want that only 50% packets will receive. I am working on centOS 5.5. For that I searched on net. I got IPtables. I used random patch of IPtables. Command sudo iptables -A INPUT -p ...
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1answer
145 views

Possible causes of high download activity on network [closed]

We had an issue where we noticed approximately 170GB of data downloaded as http traffic over a one week period on our network. After locking down many services and running a hub as an in between ...
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1answer
195 views

Capturing packets via l7filter

As a part of my Ph. D study, I compile linux-2.6.28 kernel to support in-kernel l7filtering capabilities. I'm adding a single rule to iptables with the following: iptables -t mangle -A PREROUTING -m ...
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1answer
54 views

Filter ip traffic based on certain packet bits

I want to capture ip traffic at a linux machine based on the following bpf filter: ether[45]=0x11 and ether[68]=0x34 Incoming traffic is around 20Gbps and the filter discards 95% of the traffic. As ...
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192 views

Is there a tool to do packet mirroring in CentOS 5.9?

I know iptables + xtables can do it in more recent versions using the TEE target supplied by the xtables-addon package for iptables. However, the kernel in CentOS 5.9 is 2.6.18 and this version is not ...
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212 views

Filtering inbound traffic without knowing the destination subnet

I have a linux machine configured as a router with two interfaces facing LAN A and LAN B. I want to filter traffic passing from LAN A to LAN B (inbound traffic) using tcpdump, but I don't have the ...
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2answers
3k views

using wireshark/tshark in command line to ignore ssh connections

I'm trying to debug some by looking at the packets and I would like to avoid getting all the SSH traffic to the server. Is there a way to ignore? I tried to do something like tshark -f "port !22" but ...
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145 views

Is Snort able to efficiently demux and log large HTTP POST requests?

I'm trying to debug some failed HTTP POST requests containing large file uploads (~500 MB). The end-user is receiving strange HTTP responses that are not being logged in either varnish's varnishncsa ...
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1answer
300 views

Log http data in unique files using tcpick

I'm trying to use tcpick to log http data in unique files (client and server mixed together). This is one of the examples from tcpick's man page: $ tcpick -i eth0 "port 80" -wRub I expected this to ...
2
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1answer
999 views

Why do some machines respond with many RST packets instead of RST-ACK to refuse a connection?

I have recently been trying to track down a problem with one of our systems and have noticed that it is simply not allowed to connect to a remote machine. However, the remote machine (not controlled ...