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Questions tagged [tcpdump]

tcpdump is a CLI tool for capturing and displaying packets sent and received by network devices.

466 questions
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How can I add iptables rule on particular event (HTTP/1.1 302 Found)

My Tomato based router has two interfaces Eth0 - direct connection Tun1 - vpn Sometimes some websites return "HTTP/1.1 302 Found" and when that happens, I want to add iptables rule to use Tun1 instead of Eth0 for that particular IP. I can not figure…
Maglev
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Weird behavior of VPS host

Hi I noticed strange behavior on my VPS host I launch nmap on my laptop and scan VPS host nmap screenshot Listed netstat on VPS server netstat screenshot Tried to connect to some port connection screenshot Checked tcpdump on VPS server tcpdump…
kpazik
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What does "-tnn" mean in "tcpdump -i eth0 -tnn dst port 80 -c 1000"

What does -tnn mean in tcpdump -i eth0 -tnn dst port 80 -c 1000. I didn't find -tnn on the man page, and I didn't find it on the Internet. Can anyone explain it to me?
Searene
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Why is wireshark capturing packets not destined to my host?

My IP was configured as 192.168.101.91, I don't understand why my host is receiving packets which have a destination address of 192.168.87.203(and many other IPs which I didn't capture) given that I have already shutdown my KVM and disabled ip…
xczzhh
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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 only gives me the packets I send from my IP to the…
Hikari
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can’t get any data from tcpdump from https server where i actually get the response

When i access https://xxx.xxx.xxx.xxx:5432/, i can get reseponse from the server. (https with 5432, for test purpose). But when i do tcpdump on server ‘xxx.xxx.xxx.xxx’, it doesn’t show me anything but empty. belows are what i typed and the…
jinhwan
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ping: unknown host google.com

Relevant output: /etc/hosts 127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4 ::1 localhost localhost.localdomain localhost6 localhost6.localdomain6 servers_ip_address …
Tar
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Measuring delays between various components on a localhost

I need to profile a web application from a system performance standpoint and find out for typical user actions (accessing the home page, logging in...) where the delay comes from. The website uses the following components: -apache (serving a PHP…
Max
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tcpdump related

Can anyone inform about the commands/codes through which we can perform network monitoring or debugging activity with the help of tcpdump?
nwprogrammer
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How can I see the response of the DNS requests that tcpdump is showing me?

I'm using tcpdump (for the first time) to try to debug a DNS issue: tcpdump -n udp port 53 It gives me this output: 10:38:30.431467 IP a.b.c.d.56973 > 8.8.8.8.domain: 49179+ A? ocsp.sectigo.com. (34) 10:38:30.431476 IP a.b.c.d.56973 >…
Codemonkey
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SSH connection not established, but standard TCP/IP connection works

I'm working on a custom yocto Linux for a Raspberry PI 3 and try to get the WIFI connection working with SSH. However when trying to connect from my PC (Ubuntu 19.10, SSH OpenSSH_8.0p1 Ubuntu-6build1, OpenSSL 1.1.1c 28 May 2019) to the PI on which…
deets
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Using tcpdump to find strings

I need to block certain TCP packets by trying to find a string match in and on them. Is there a way to do that with TCPDump? Or do I need wireshare install on my linux server? One I have the string IPtables can be used to block a string If I…
Jake Thomas
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TCP dump used for and how can it be used

What are the advantages and benifits of TCP dump and how can this be used and in which environments it can be used
developer
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Filter tcpdump capture to gather info on DNS/URL/URI

I'm looking to extract the DNS/URL/URI information from packets and produce a CSV output which I can then feed into flowtag.
Stefan Amyotte
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how to sniff from a remote machine?

I have a PC and a tablet that connected to a TP-Link ADSL modem. PROBLEM: I want to see the packets that send and receive from my modem not my PC( to see both wire and wireless packets) I search very places for do this but I can't sniff from…
goodman
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