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Questions tagged [tcpip]

TCP and IP are two important protocols used in networking today. Due to their importance, the Internet Protocol Suite is also commonly known as "TCP/IP"

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tcp previous segment not captured

I'm attempting to remotely control a device with c code. I could not send commands. I'm also not able to see the commands entering Wireshark either. Whenever I execute the code, it displays the error ...
Beyza Sezer's user avatar
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1 answer
101 views

Can two LAN networks both at one level behind a router higher up the routing chain use the same subnet mask and network ID? [duplicate]

Can two LAN networks both at one level behind a router higher up the routing chain use the same subnet mask and network ID? See the diagram below. This question was already answered here, but I am ...
riverofwind's user avatar
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Is there a way to detect which requests have been made using same connection in Apache log?

I use mod_log_config and mod_log_forensic to log all requests made to an Apache server. Some of those requests use Keep-Alive and I would like to find out which requests have been made using the same ...
tigrou's user avatar
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1 answer
80 views

Change DHCP range and tcpip connections

I want to change the dynamic range of my DHCP server for a network e.g. it is at the moment from 192.168.0.2 to 192.168.0.100 I want to move it from 192.168.0.101 to 192.168.0.200 but I don't want to ...
AAB's user avatar
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1 answer
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Iptables rule to capture DHCP I/O fails

I have stumbled upon a peculiar issue with Iptables. I am not seeking a solution to a problem, but an explanation of some strange behaviour of iptables. My platform is Ubuntu 22.04.2 LTS with 5.19.0-...
storestyggeulv's user avatar
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1 answer
516 views

Continuous [ACK]Packets Without any Response From Receiver

Our application sends some data to one of our devices via TCP/IP, However communication in between not working as it should be.Because TCP/IP is bidirectional, so if one side sends data to other, ...
Batuhan Zorlu's user avatar
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1 answer
246 views

How to find out if TCP connection to server is being tampered with by third-parties?

I'm under an unreliable ISP/AS, something like the GFW. They actively try to sabotage a TCP+TLS session by attacks such as sending SYN RST to established connections, making the connection timeout, ...
Ragahito's user avatar
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2k views

How can I connect two routers to the same switch

First of all, I'm not talking about those all-in-one routers that do wifi/switching/routing. It drives me nuts when people call a Wifi box a "router". Anway, I would like to do the ...
7wp's user avatar
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72 views

TCP Session drops because of FIN signal

I have two servers communicating with each other through ISO 8385 messages over TCP sessions. Basically host-to-host interface between two payment switches. The problem is that the session keeps ...
Mohammed Tellesy's user avatar
1 vote
2 answers
93 views

Are there any additional security considerations to be taken into account when activating IPv6 as opposed to IPv4?

As a sysadmin, I'm fairly experienced with IPv4. As such, I feel comfortable configuring firewalls to expose servers/services to the Internet with public IPv4 addresses. I have a basic understanding ...
Heinzi's user avatar
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-2 votes
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Can two servers talk to each other via TCP by this configuration? [duplicate]

This is an interview question: There are two servers on Rank A, setup the network on the two hosts by following configuration: Server A: ifconfig eth0 10.10.15.129 netmask 255.255.255.0 up route add ...
J JIA's user avatar
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2 votes
0 answers
162 views

Long latency to reply a TCP ACK

k8s environment(4 nodes, rke 1.21.5) We noticed there is randomly significant latency in socket data transferring between different k8s pods. Latency could be as long as 15 seconds in some cases. By ...
skyfire's user avatar
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7 votes
2 answers
13k views

Docker container unable to connect to one specific external IP, yet host can

This is a puzzler, and I'm hoping that by writing a StackOverflow question, I gain some fresh insights. In a nutshell, I'm trying to figure out why I can access https://sts.nih.gov from a host machine,...
Paul Dixon's user avatar
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TCP packets being lost

I have some TCP packets being lost. I have monitored the interface with tcpdump pcap file - https://www.dropbox.com/s/7m3hr1b7065tenx/tcp.pcap?dl=0 I noticed that when I lose packets I only get 5 ...
Ruby dev's user avatar
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Is there a registry value to force a connection to close?

I have an ethernet connection that I want to close if it's not sending or receiving any data. Is there a registry value I can set or any configurations I can change? For windows 10, thanks Edit: ...
user1416658's user avatar
-1 votes
1 answer
765 views

Getting the MAC address of a remote host? Linux, macOS, Linux [closed]

I am writing a custom application in Go. My app needs to work on Linux, macOS, and Windows 10+. I need to verify that a remote host is what I think it is. I've tried arping and as expected, it does ...
PrecisionPete's user avatar
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1 answer
1k views

Having Trouble Identifying TCP Congestion Control Provider option: Default

I am running a Windows 10 (Version 1909) OS and when I am entering the following command in CMD ... netsh interface tcp show global ...I am able to see add-on congestion control provider set to "...
DeathS7roke's user avatar
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2 answers
5k views

http timeout with docker bridge network, but port 80 is opened in firewall

I'm trying to install mailcow-dockerized in my server, but I'm having trouble with Docker network. I tried several ways, but I get lots of connection timeouts in containers. In order to breakdown the ...
marcofons's user avatar
0 votes
1 answer
1k views

APIPA ARP requests are send all over the network

We have ~200 hosts running windows 10 and ~40 ip cameras all working with ip addresses from 10.100.0.0/16 almost all of them sending arp requests to 169.254.0.0/16. We have also virtual machines ...
v.doro2's user avatar
-1 votes
1 answer
121 views

Transport layer port and firewall

When a communication is initiate the OS chooses randomly a port number greater than 1023. As long as it does not conflict with other ports in use on the system at that moment. I wonder how the ...
ragnar's user avatar
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0 votes
1 answer
1k views

Routing Issue: Cannot reach target server from local network

1. my setup: I've got an optical fibre ZTE router from my ISP for internet and telephone. My old analog phone is connected directly to the router using the dedicated phone port on my router. (For ...
hans2020dieter's user avatar
1 vote
0 answers
282 views

TCP handshake not completing intermittently to specific Cloudflare node

I have setup a webpage with Cloudflare that works nearly all of the time, except occasionally the TCP handshake fails with the SYN+ACK not making it to Cloudflare. On a packet capture from another ...
Erik Johnson's user avatar
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1 answer
191 views

HA Proxy TCP Content Rejection

I am looking for an option or a work around where I can accept or reject the TCP Content based on the the size of a file which is getting uploaded This settings is required on TCP IP layer only also ...
Suketu Shah's user avatar
1 vote
0 answers
666 views

How to load balance Socket Connections?

We have a large pool of devices that establishes socket connections with a server. Connections are TCP socket connections hitting a server IP: port pair from a destination IP port pair. In stand alone ...
ramdaz's user avatar
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1 vote
1 answer
503 views

Is it redundant to add an extra checksum or CRC in TCP packets to make it possible for the receiver verify whether the data is same with the sent one?

As TCP contains a checksum and the TCP/IP stack will detect broken packets, is it redundant to add an extra checksum or CRC in TCP packets to make it possible for the receiver verify whether the data ...
John's user avatar
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1 vote
1 answer
447 views

Is it useless to reply the received messages (on TCP) on application layer to tell the sender the messages have been successfully received?

Any data loss is detected and automatically corrected, which is why TCP is also called a reliable protocol. In other words, the transport layer is responsible for error-free, end-to-end delivery of ...
John's user avatar
  • 149
-1 votes
1 answer
974 views

Python sockets: TCP errors in linux, while same program works fine on Windows10

I'm trying to communicate with a commercial power supply device via TCP/IP using python sockets. I tried using both a virtual linux(centos8stream) and virtual windows10, both running at the same ...
Cenkoloji's user avatar
1 vote
0 answers
142 views

Determine if there's Network Traffic over a TCP/IP Connection using PowerShell in Windows?

I had a situation where an application was "hanging" in accessing the database. I was able to see that there was a connection by using Get-NetTcpConnection -RemotePort x This showed that ...
John Saunders's user avatar
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2 answers
354 views

How to forward client ip to App server via Haproxy TCP/IP loadbalancer?

I have configured HAproxy for TCP/IP loadbalancing but in app server I am not getting IP address of source instead of that I'm getting haproxy IP address as client ip address. I searched on google and ...
John The Hacker's user avatar
0 votes
2 answers
80 views

TCP/IP: can i REMOTELY (via VPN) access mis-addressed device on remote LAN?

i sent a pre-configured box to client to drop onto their LAN. while i was sure i left it as DHCP, when i connect to the LAN through the VPN i'm not seeing it pull an address from the router and it ...
WhiteRau's user avatar
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0 answers
597 views

Linux TCP stack does not send a RST after giving up on retransmissions

Several sources (one being my colleague and the other being TCP/IP Illustrated by Stevens) indicate that there should be a RST sent after the TCP retransmission attempts have been exhausted. I have ...
Zvej's user avatar
  • 1
0 votes
2 answers
52 views

Login attempts from 255 IP? (3.0.115.255)

today I see some login attempts from an unusual IP: 3.0.115.255 and I ask myself: how can this happen, that an IP ends with 255? I thought it's for broadcasting - can it be assigned to a single ...
mathse's user avatar
  • 3
1 vote
1 answer
636 views

AutoSSH monitor echo port bind to specific IP

I'm using autossh for create ssh tunnel. Everything good excep paramiter -M of autossh. It cannot bind to specific IP to remote host. By default, it create 0.0.0.0:20000. I wanna bind to loopback IP: ...
Moni Pop's user avatar
1 vote
1 answer
205 views

Proper behavior for a DNS Server when it is queried for a domain it doesn't control in the case of Split-Horizon DNS?

So one of our cloud providers offers a lower-latency, zero-rated "Internal Networking" option between VMs. The interfaces on the internal network are in the 10.x.x.x IP Space. When one of ...
Jonathan S. Fisher's user avatar
0 votes
0 answers
231 views

What would be the possible reason for server not send syn/ack pack for specific IP address?

we have a server that do not respond to a specific internet IP address. We have looked into firewalls but no obvious setting showing block the IP. From wireshark, we found that the server received syn ...
Shore's user avatar
  • 101
-2 votes
3 answers
2k views

DNS and OSI Layer Working

I would like to clarify a doubt that's haunting me after learning DNS. I'll briefly write it as a question. "A user was watching a video in youtube and suddenly the DNS server which was used by ...
itSupport's user avatar
1 vote
0 answers
747 views

Linux connections to unused port timeout instead of being refused

I have a Centos 7 box I inherited where if I try to connect to an unused localhost port, the connection fails with a timeout instead of being immediately refused. Example below: $ nc 127.0.0.1 5800 ...
pcarter's user avatar
  • 107
1 vote
1 answer
1k views

Forwarded Packets are received by namespace's veth0 but not received by application

I use libtins (It uses Pcap) to capture link layer packets and forward to a network namespace where the actual application runs on. Client(Browser) -> Server -> Pcap -> Pcap Send -> br0 (...
sqlbie's user avatar
  • 11
0 votes
3 answers
1k views

Sending files via FTP without IP addresses on PC's [closed]

Can two PC's communicate with each other - FTP, without using IP addresses(entirely skipping Network Layer)? I know, FTP is client-server architecture, but I wonder if LAN network and MAC addresses ...
Rafal's user avatar
  • 3
0 votes
1 answer
423 views

How does a PC determine which network adapter to use when given an IP/DNS to connect to? [closed]

I have so many network adapters on my PC. If I type for example "Ping 192.168.191.128", how does my PC now which network adapter to use? What if it's a DNS name like "mylocal.ddd.com&...
user1034912's user avatar
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0 votes
4 answers
309 views

Stop attacker without affecting others on same IP [closed]

How can I stop a client that's running a multirequest script on my server that reconnects and continues no matter what, without affecting the other people/clients that are connected to my server from ...
Arre's user avatar
  • 3
0 votes
1 answer
1k views

How to enable ECN marking in IP header in Linux

Is the ECN marking in the IP header is performed by default in Ubuntu (4.15.x kernel) or should the kernel be recompiled with a special option? I configured a RED ingress queue at an Ubuntu machine, ...
v1mm3r's user avatar
  • 1
-1 votes
1 answer
944 views

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, ...
deets's user avatar
  • 1
0 votes
1 answer
121 views

What do i need to take to connect an openvpn server to a local network?

I'm setting up an office vpn so people can work from home, by rdp'ing their office machines by connecting to a vpn server which is based on the office lan. It wont be as simple as creating a vpn ...
AlexH's user avatar
  • 1
-1 votes
2 answers
760 views

Is it actually possible to send some data to remote destination over tcp/ip without any socket? [closed]

I am studying socket concept. As far as I learned socket is like electrical socket that is created in both end of communicating devices (or processes). Socket can keep itself alive forever to listen ...
Shamim's user avatar
  • 101
0 votes
1 answer
418 views

Ping a host in other network

I have a Virtual Machine One in inner network 192.168.1.0 with ip address 192.168.1.1 and Machine Two in inner network 192.168.2.0 with ip 192.168.2.2. Both have enp0s3 interface. How could I ping 192....
FuryMaxim's user avatar
0 votes
1 answer
222 views

TPC lost segment

I'm investigating an issue where the application (Java based) didn't receive the whole message which was split on two TCP segments. I have a trace that proves that both segments was sent to the server....
Pavlos Maragkos's user avatar
0 votes
1 answer
7k views

How to add more than 2 DNS servers in a domain

I have 3 DNS servers in my environment that I'd like to show up on my end users machines for backup. 2 onsite and 1 in Azure. I have a site 2 site VPN connection between HQ and Azure. When I go to ...
gchapmangt's user avatar
0 votes
1 answer
3k views

Windows Server 2012 R2 SYN Flood Attack?

I have a Windows Server 2012 R2 IIS web server, running on VMWare esxi 5.5, hosting multiple websites with different IP addresses. This server recently has been refusing connections randomly across ...
awilinsk's user avatar
  • 332
0 votes
1 answer
2k views

How do I bind to UDP port 53 in GCE (Container-Optimized OS)?

Is there any way to free up UDP port 53 on my GCE instance so that I can bind to it? I'm running a container on GCE that needs to listen on UDP port 53, as it's listening for DNS connections. However,...
Aaron H's user avatar
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