Questions tagged [packet-capture]

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).

Packet capture is the act of capturing data packets crossing a computer network. Deep packet capture (DPC) is the act of capturing, at full network speed, complete network packets (header and payload) crossing a network with a high traffic rate. Once captured and stored, either in short-term memory or long-term storage, software tools can perform Deep packet inspection (DPI) to review network packet data, perform forensics analysis to uncover the root cause of network problems, identify security threats, and ensure data communications and network usage complies with outlined policy. Some DPCs can be coupled with DPI and can as a result manage, inspect, and analyze all network traffic in real-time at wire speeds while keeping a historical archive of all network traffic for further analysis.

Partial packet capture can record headers without recording the total content of datagrams. This can reduce storage requirements, and avoid legal problems, but yet have enough data to reveal the essential information required for problem diagnosis.

Source: Wikipedia.

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How to turn an ethernet port into a passive listener?

I want to capture ethernet packets with my raspberry pi's ethernet port. I know I could create an ethernet bridge between two ethernet ports on the raspberry and analyze the packets internally with tcpdump. But I need the entire thing to not rely on…
guerlando
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rpcapd behind a firewall

I have a remote server with rpcapd installed that follows strict security policy rules. Any client can access to the server only via firewall that follows same security policy (please, don't blame me, it wasn't my idea). The only port opened on the…
enzo
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Port forwarding for 100K+ IP's

I need to do port forwarding on my Linux (Debian 8) to intercept packets going through the machine. It needs to be based on source IP, so different ports for different IPs. I've though of using iptables ex. iptables -t nat -A PREROUTING -s…
Alfred Balle
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Who can issue a RST?

I have a client connecting to a server via a VPN tunnel. The connectivity is in place, I can ping the server and requests some other services (a curl request on an API for instance) through that tunnel. One service on the client cannot bind to the…
WoJ
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Cisco 877 doesn't respond to IP determined through ARP

I have just obtained an old Cisco 877. I made sure to first push the reset button in the back. I then plugged into one of the LAN ports. The device gave me an IPv4 address (169.254.14.65/16) and an IPv6 address (fe80::9504:ecb9:b0b:e41%38) I tried…
Stringers
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How can I identify the cause of packet loss in DNS?

We have upgraded some of our routers to Ubuntu 16.04 and are now getting some performance problems with DNS. It seems that packets are sometimes truncated, but I have no clue what else I can do: This are the messages from logfile: Jun 8 10:33:01…
Thomas
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How do I generate a source of netflow data for nfcapd?

I am trying to use nfcapd to save netflow files for use by a network analysis tool. How do I capture network traffic on my host and send it into nfcapd? Can I use wireshark/tshark or something similar?
aaa90210
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How to filter wireshark capture to have only packets with local ip as source or destination

How to filter wireshark capture to have only packets with local ip as source or destination? The expression should be valid for both ipv4 and ipv6. I am obviously asking for an other solution than that of finding the ipv4 and ipv6 manually and…
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how can i export sflow data to be saved in pcap on other server in realtime?

I have a pfsense server, all of attacks will come to its WAN interface. i have setup another packet analysis tool on private network behind pfsense. i want to send realtime WAN traffic from pfsense WAN to backend private server, which is listening…
Farhan
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In the output of Chaosreader, where are the source and destination port numbers and IP addresses for each packet?

I used this tutorial to use Chaosreader on an output file of WinDump. My purpose was to get the HTTP payload, which I got. But I'd also like to extract other information, like source IP and destination IP, source port and destination port, for each…
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packet colorization in Wireshark

is there anyone who could sum up the packet colorization system in wireshark? My capture list is looking quite colourful, but I don't quite understand how the colorization scheme work. Thank you
m.rossi
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How to perform Wiresharks File->Extract Objects->HTTP through Tshark commandline interface?

Using TShark, I want to be able to extract the payload in HTTP response from packets data captured through tshark in a .pcap file. In the Wireshark GUI, I was able to do that by File > Extract Objects > HTTP, and then choosing a file from the HTTP…
Jesss
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Why do some VLAN Wireshark captures include data after the IPv4 payload?

Data Some Cloudshark captures show a "Trailer" for the vLAN and some do not. Captures With extra 4 bytes. Without extra 4 bytes. Question Why do some and not all VLAN Wireshark captures include data after the IPv4 payload?
Klik
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Is it possible to specify tcpdump that I want it to interpret packet differently before printing it to STDOUT?

I am using iperf to pinpoint packet reordering issue. Unfortunately, tcpdump does not know how to parse iperf's UDP payload that I could use to pinpoint the issue. I know that iperf stores packet sequence ID in the first 32-bits of the UDP…
john1234
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Why are ICMP packets not captured on the target interface?

I have a network setup as in the picture: The central box is a gateway (Ubuntu 15.10) which relays the packets betwen the various networks (only one is shown on the picture - lan0) and Internet. gateway: I can ping all interfaces and hosts on…
WoJ
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