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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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32 views

Windows Server 2011 - System opening ominous TCP connections

Where I work we have a Windows Server 2011 Small Business edition, and recently our Symantec software started reporting "blocked intrusion attempts" from port 80. Our routers do not forward any port ...
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1answer
59 views

Sysinternals Sysmon: How to log an unsuccessful TCP/IP connection attempt

I would like to use Sysmon to log an unsuccessful TCP/IP connection attempt. For example, with the following configuration: <NetworkConnect onmatch="include"> <DestinationPort condition="...
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1answer
62 views

why are there are so many svchost established connections to Isilon?

Our client has a Isilon (used only for smb) with few nodes attached to it. When I run TCPView I don't understand why svchost service established the connection and why there're so many of them: And ...
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1answer
21 views

Which parameters and setting affect network throughput when connecting two machines together without a switch?

I have a situation where I need best possible throughput (TCP/IP sockets & SMB3) between two Windows Server 2016 connect with a 1m patch cable. I have to use existing hardware. When you connect ...
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1answer
27 views

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 ...
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0answers
39 views

hping3 does not send sequence and ack numbers as specified?

To be precise, I am sending a TCP Ack Packet setting my own manual seq and ack values but the result is different than entered in wirshark. Command: hping3 -s 8000 -p 8000 192.168.1.95 -M 1 -L 1 -A ...
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3answers
88 views

diffrence between csma/cd and tcp/ip

I finished my middle school IT & Networking education about 2 years ago. Now I recently got a job and started to refresh my knowledge. I've been searching the internet first of course but I still ...
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4answers
488 views

Windows 7 Client flooding network with DHCP requests. Not setting IP

I have a small network, with 15 workstations, SAMBA AD, and a bunch of Virtualized linux servers. All the workstations, and servers are on the same subnet. All workstations are running Windows 7 Pro ...
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1answer
206 views

TCP Initial Handshake Incomplete (ACK Missing)

I am irritated about the following scenario: I am running a MVC application on an IIS 10 Webserver. While calling the URI, it takes about 10 seconds until the application starts to get called (IDLE ...
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1answer
237 views

Why does TCP request packet contain ACK flag? [closed]

I am very new at low level of TCP and I am tryingtcpdump with simple socket server and client program. The server and client follow the two steps. Server and client make a connection. Client sends ...
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2answers
1k views

Linux: tracking the source of netstat -s “failed connection attempts”

I have several servers, where the failed connection attempts metric returned by netstat -s (from /proc/net/snmp) grows by roughly one per second, and I'd like to diagnose the source of these. By ...
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1answer
42 views

can only ssh unidirectional

I have two centos 7.2 server. One machine ip is 10.104.196.18, another machine is 10.240.197.21. I can successfully ssh from 10.104.196.18 to 10.240.197.21. But failed to ssh into 10.240.196.18 from ...
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1answer
76 views

ARP responses from host with several interfaces

I have a (experimental) setup where a host myhost.mydomain has three network interfaces all connected to the same VLAN as its default gateway mygateway.mydonain. The setup looks as follows: interface ...
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1answer
190 views

How do I get Kubernetes to work without the “connection over port 8080” error?

I installed Kubernetes in RHEL 7.x. I expect kubectl commands to work without errors. Port 8080 is not being blocked from my client workstation to the RedHat server with Kubernetes. I tried several ...
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0answers
65 views

OpenVPN network as part of server subnet

I have a server connected to network 192.168.200.0/24 it is our local network office's and 172.20.0.0/16 it is VPN network shared in office. And I have install OpenVPN server on the same server in ...
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1answer
246 views

MaxUserPort setting seems to be ignored

One of my .NET applications is getting the following exception when firing ~300 HTTP requests in a span of about 1 minute: System.Net.WebException: Unable to connect to the remote server ---> ...
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0answers
132 views

Is direct hosting SMB 3.x over TCP standard or optional these days, if optional how do I make my computer use it?

I just came across this page ("Direct hosting of SMB over TCP/IP"). It's quite old, so I can't be sure if it's the standard these days. It refers to disabling NetBIOS over TCP and disabling WINS, ...
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1answer
512 views

Windows Server 2012 R2 can't establish outgoing TCP connections

I've got a very weird error in a server. It is a Windows Server 2012 R2 Standard Domain Controller (primary) running in VMware ESXi 6.0 U2. It has DNS, DHCP and some file shares. The error is that it ...
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1answer
135 views

Slow UNC paths on virtual Windows Server 2008R2

We have a virtualized Windows Server 2008R2 running on a host Windows Server 2012R2. The 08R2 server is also running SQL Server 2008R2 SP3 (Version 10.5) and IIS 7.5. Lately we've had intermittent ...
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2answers
553 views

How do I allow communication between two Azure virtual networks with their own VPN gateways

I need some help (or maybe a better angle of attack) connecting a few external users to our Azure tenancy. NOTE: All resources mentioned below are in the same Azure Subscription, the same Azure ...
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2answers
96 views

What happens to a tcp packet when two access points for the Same SSID are on the same channel

Working on a C# Tcp server that is communicting with an embedded IOT device and I was having serious communication problems. Packets getting lost and or delayed. Not receiving ACK...ect It turns out ...
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2answers
332 views

Checking open rdp ports from script

I need to find out what server ports are listening on port 3389. I have to check 2500 servers, some in different vlans, to make sure remote desktop is enabled. Can netstat be used to check this and ...
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2answers
494 views

OVH : SSH Connections Timout after multiple connections

So i have making a control panel of sorts with php on my webserver that is able to send commands to my dedicated server (remote server) via ssh2. This works fine, however i have noticed that after a ...
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2answers
73 views

How to understand the “A subnet Example”?

In A Subnet Example of TCP/IP Illustrated, Vol. 1: The Protocols , there is a Figure and a table: and under the thick Line in dash rectangle, there is Ethernet, subnet 140.252.13.32, and in table, ...
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1answer
83 views

route loop while ping one server with 3 NIC in 3 separate networks

I have this server used for testing some network parameters. It has 3 separate network cards, each with the below IP configuration: 192.168.10.150/30 gw 10.149 192.168.152.146/30 gw 152.145 192.168....
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1answer
569 views

How can I force a linked SQL Server to use TCP/IP instead of Named Pipes?

I have a SQL Server instance, Instance1, that has a linked SQL Server, Instance2. The linked server technically works, however I am positive that Instance1 is connecting to Instance2 via Named Pipes. ...
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0answers
823 views

what does TCPV4 connections established perfmon counter mean?

We have around 60 windows based SMTP servers behind a load balancer. Out of these one server is taking significantly less traffic (1/10th) when compared to remaining servers. From perfmon, I see high '...
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1answer
258 views

Terminal Command to find maximum allowed TCP/IP connection on a port in Apache server(CentOS)

Is there any terminal commands to check the maximum allowed number of concurrent TCP/IP connections can be done in Apache server with CentOS??
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1answer
1k views

TCP Handshake error: SYN and SYN/ACK packets are not recognised

I have very interesting problem: I have Proxmox hypervisor and two linux vms on it: First vm have several nics in main bridge, each nic added to vm with certain vlan tag on hypervisor. Second vm ...
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1answer
677 views

Can't connect to specific IP address and/or TCP port - can the ISP be blocking it?

I have a RDP user who has successfully been using RDP from his laptop to his workstation in our office when he is at home. It is configured to use our public IP and port 10378 and has been working ...
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0answers
48 views

Windows 2003 dynamic ports rellocation

After digging the internet for a way to relocate the dynamic ports start number and range... I found the following registry settings... HKLM\Software\Microsoft\Rpc\Internet (Key) \...
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1answer
192 views

Debug ISP connection issue (Pfsense bogon network list out-of-date)

I have access to the office from outside (VPN, e-mail, etc.). I have at home Internet from ISP(A) and at office from ISP(B). Everything were working fine till I received an e-mail from my ISP(A) that ...
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1answer
300 views

What could be stopping DHCP from a computer connected to a specific switch?

I've recently replaced a number of 10/100 switches in our office with Gigabit managed switches and I've found that computers connected to one of the switches aren't getting DHCP leases from the server....
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1answer
46 views

Client and Server on the same Computer

I have an OPC UA Server and an OPC Client running on the same computer communicating via TCP/IP. What's the pro and cons using 127.0.0.1 vs IP address of the network card?
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1answer
78 views

how to force OS using which alias ip address

i have a server running debian with 2 ip address : eth3 44.44.44.1 eth3:0 44.44.44.2 the problem is my outband request goes with second ip address "44.44.44.2" how can i force OS to use primary ...
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4answers
304 views

Connect two TTYs via TCP/IP

I have two computers running Debian and connected via Ethernet. They see each other. I need to connect two virtual terminals on this computer this way: anything I input in first terminal will be ...
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1answer
183 views

WIndows is not following TcpAckFrequency settings

This is a wierd one. I have set the tcpackfrequency to 2 and windows does not seem to honor it no matter what I do. I would need your help with this. My current template is Internet and congestion ...
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1answer
144 views

Irresponsive nginx while doing “nginx reload”

While reloading nginx, I started getting errors in messages log "possible SYN flooding on port 443", and it seems like nginx becomes completely irresponsive at that time (quite for a while), cause ...
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1answer
371 views

SYN flooding on port 443 while nginx reload

While reloading nginx, I started getting errors in messages log "possible SYN flooding on port 443", and it seems like nginx becomes completely irresponsive at that time (quite for a while), cause ...
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0answers
155 views

Windows 7 suppression of tcpip event 4199

I've noticed that Windows 7 doesn't raise event 4199 (Duplicate IP on network) consistently when assigning static IP addresses to machines. If we configure 2 machines correctly with non-conflicting ...
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0answers
52 views

No Network Traffic Between Host and VM

I have a virtual machine running that I wish to connect to a physical piece of hardware via an Ethernet connection from the host machine. This piece of hardware requires a specific IP address to be ...
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1answer
3k views

TcpTimedWaitDelay is missing in Windows Server 2012

Suddenly my server log shows: An operation on a socket could not be performed because the system lacked sufficient buffer space or because a queue was full And I googled and found these links as ...
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1answer
165 views

Windows server 2008 R2(standard) client connection is very slow after connecting above 24 client machines? Is there any client connection limit?

Windows server 2008 r2 standard is connecting 24 cilent machines after while adding extra machines to server it gets slow. In Windows server 2008 r2 maintaining the mysql database and all other client ...
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1answer
660 views

Connection SSH port 22 via domain name but not public ip address

I have a Draytek router configured to port forward SSH connections to an internal server from specific ip addresses only. Clients and myself can connect externally successfully except one who cannot ...
8
votes
2answers
2k views

How to configure iptables so an unwanted port is not reported as filtered

I'd like to stop others from seeing my ports as filtered in the nmap standard scan (unprivileged). Let's say that I have the following ports open: 22, 3306, 995 and a firewall configured like this: -...
1
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1answer
220 views

what are the implications of running a FQDN as internal AD domain and point A-record for website to different host?

The MSP for a law firm office that has just joined our company is using a FQDN as an internal AD Domain and has been doing so for sometime apparently. They have this issue in that they have a website ...
2
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1answer
569 views

Ephemeral port reuse for TCP connections to different IP addresses

I know that a web server running a website on TCP port 80 can receive TCP connections from many different IP addresses sourced from many different ephemeral ports. Can a client initiate multiple ...
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1answer
397 views

Why does one of my LAN servers frequently require 21 seconds to connect?

Using a mix of Windows 7 and Windows 10 clients, one of my LAN servers tends to take 21 seconds to establish a connection. This LAN server is running Windows Server 2012-R2 and hosting TFS 2015 on ...
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1answer
48 views

Two subnets on one LAN

I have a simple 192.168.1.x/24 LAN GW & DNS = 192.168.1.254 My workstation is 192.168.1.101 I wish to setup a parallel mirror LAN for testing using a 192.168.10.x/24 subnet on the same switch. ...
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0answers
27 views

How to I diagnose downloads slowing over time?

I am trying to track down a strange networking problem. Basically, a http download from a tomcat server is slowing down over time. For example, the download speed starts at 700kb, then slows to 650, ...