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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A local IP address (RFC 1918) on my network that is not … local

I've noticed an IP address today on my network (192.168.15.1) which when visited actually goes to a page that has a router webconfig page (Not my router) The puzzling thing is that i tried traceroute ...
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26 views

Event id 4227 tcp/ip warnings on Windows 7

We're deploying a new image out to the field, and we're seeing tcp/ip event id 4227 warnings periodically throughout the day (1-3 a day). The event message reads as follows: TCP/IP failed to ...
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2answers
37 views

ASN number basics [closed]

I have the basic idea of ASN numbers. My question is how do routers know about them? It doesn't seem like it is signified by any bits in the datagram, so I assume it's done in the protocol. Once you ...
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10 views

Cannot ping to default gateway from computer inside private network [migrated]

I have one desktop PC, laptop and android mobile. I have created a WiFi hotspot on my desktop PC so that I can use my internet on mobile as well on a laptop and it's working great, but now I want to ...
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1answer
34 views

high availabilty port forwarding in mswindows

I need port forwarding for a mswindows host, but I need something which can handle more than one target with fail over. There are no end of tools to do this on Linux/Unix (haproxy, balance, ...
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40 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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53 views

Why I cannot access EC2 instance public IP from inside of instance itself?

Here is an example, I have an Linux instance , say, private IP is 10.10.10.10, public IP is 54.54.54.54. Inside the instance, I could successfully ping it's private IP(10.10.10.10) and localhost. ...
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13 views

Can a firewall handle packets being sent to it by a network TAP?

We have the intention of examining incoming mails for security purposes. In order to do so we figured out the solution will include: Network TAP - To copy all SMTP traffic to the firewall Firewall - ...
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139 views

Can a port be in the listen state and be closed?

Servers running Debian7.7, Mongodb 1.2.0.6-1.1, Nmap6.0 - Thanks for your time. I've user who can't connect to mongodb from his Win7 desktop. He has mongodb installed on it and he's trying to connect ...
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81 views

TCP: out of memory - Nginx

I'm running a high traffic site on a nginx server. Last fews days I'm having problems with my VPS locking up (unable to SSH, and nginx seems to be down). When I look in the logs I can see the ...
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1answer
117 views

How does Windows 2008 specifically select ephemeral ports (does it test to avoid conflicts)?

I have a server application which uses permanently connected incoming ports within the range that W2k8 now uses in the IANA recommended range of ~49000-65000. (For legacy reasons it's extremely ...
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46 views

Outbound TTL of TCP/UDP connections on Server 2003 changes to 1

We have 4 2003 servers in an environment. Earlier this week, we had a problem where two of servers suddenly were unable to access the internet. Here's an overview of what I determined through ...
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49 views

sshd with port forwarding left connections to localhost without counterparty process

After temporary tunnel setup from X.X.X.X , from where I ran ssh -R 1089:localhost:1089 for several days, I have noticed this. I wonder what processes is 2494/sshd connected to, as no counterparty ...
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2answers
1k views

TCP Dump, cannot understand these 4 lines?

I need support understanding these 4 lines. looks like tcp dump but im actully not understanding what exactly is happening here. 13:13:22.407445 IP 192.168.246.128.54955 > 192.168.246.13.80: S ...
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34 views

An already acknowledged data sequence number is coming back as null byte repeatedly

There is a transaction processing server (TP-Server) to which my application (Client) connects to. We are seeing a strange packet sequence where in the TP-Server is sending a PUSH packet with a null ...
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3answers
2k views

How does the HTTP GET method work in relation to DNS protocol?

I am trying to understand application layer protocols in TCP/IP stack. I know that both HTTP and DNS protocol stay at the top layer (Application Layer). So, when a browser wants to access a resource, ...
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44 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
179 views

External DNS takes a long time to resolve for AD computers

On our AD domain, end users desktops take a long time to resolve DNS from outside our company. Internally everything works fine. The desktops are pointing pointing to 192.168.2.4 and .6. Those are ...
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203 views

Connection Timeout Issues - Solaris 11 SPARC

We're currently running some performance tests using Solaris 11 (SPARC) on some large hardware. The tests, which consist of sending SOAP requests (50kb per request), are running well up until we get ...
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2answers
4k views

What is [PSH, ACK] doing during my connection to a global catalog server?

A linux server of mine is trying to establish a LDAPS connection to a global catalog server and the connection is getting dropped (presumably by the GC side). For the purpose of discussion, let's ...
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1answer
692 views

Port forward remote desktop without a gateway over 3G modem router [closed]

I'm trying to connect from a laptop, through a VPN, and a 3G modem/router, to a remote PC / computer. PC (192.168.1.33) | 3G Modem (192.168.1.22) | [3G internet, connecting to VPN] | ...
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91 views

Incoming tcp SYNs possibilities

This might be a general TCP question. Can I receive TCP SYN packet on an established connection OR a connection in TIME_WAIT state? Is is possible?
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631 views

When a server IP changes, do exising TCP (e.g. http/mysql) connections remain running

We have some PHP-FPM servers and when they need a database connection, they connect to an HAProxy server which selects them a database server to use and the connection opens. When we then want to ...
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1answer
68 views

How to compare 2 TCP/IP stacks or implementations? [closed]

I have to recycle an old machine into a networking node for managing TCP/IP connections and PPP protocols ( basically a DSL connection ); I'm not asking for something more than this, all the tasks ...
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288 views

Windows Server 2008 Enterprise - Print Server Role - TCP/IP Print Server Service Won't Start

I have a few Windows Server 2008 Enterprise edition Servers running Printer Server Roles. On these servers there are two system services: Print Spooler and TCP/IP Print Server (LPDSVC). The TCP/IP ...
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1answer
263 views

Host doesn't send ACK-SYN packets for transparent proxy

I am setting up a transparent proxy using haproxy, the setup works without the 'source 0.0.0.0 usesrc client' line. When I add that line in, the endpoint is called from the original client's ip ...
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1answer
59 views

What is the incentive to operate a TCP/IP node? [closed]

I mean, why does anybody relay messages to other nodes? Why are these eleven good people below helping me send my bytes to their destination? traceroute to stackoverflow.com (198.252.206.140), ...
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2answers
1k views

Can you use WMI to determine if a connection gets its DNS servers from DHCP?

The DNS server search order for a network interface can be read from Win32_NetworkAdapterConfiguration like this in Powershell, or programmatically using .Net ManagementObjects: > $NICs = ...
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58 views

Printer lpd daemon refuses print job if a command's new-line sent separately — bug?

I'm encountering some printer LPD daemons which work fine if the new-line is sent in the same packet as the command, but break if the new-line is sent in a separate packet. Is that a bug in these ...
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1answer
106 views

TCP client and server work for X times but hang after that

I'm a software engineer, but I think my problem needs a network engineer... For the software side of things, have a look at my Stack Overflow question: ...
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2answers
876 views

List of TCP & UDP ports known to be used by malware, etc [closed]

Where can I find a regularly updated, downloadable list of TCP & UDP ports that are known to be commonly used by malware, trojans, etc.? This is for import into an IT asset management system to ...
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Firewall Connections fail to open under load

Problem : During High load , our applications are encountering errors : java.net.connection Time out. After some investigation , we found out that it was Firewall the root cause, but still don't know ...
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126 views

Could the IPG parameter in Robocopy cause TCP/IP packet problems if it is too high?

I need to throttle a robocopy transfer to limit bandwidth usage. It is already set to 1500 (/IPG:1500). I would like to increase this IPG to around 2000 (or more) in order to lower even more the ...
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2answers
311 views

once in a while windows / .net application ignores the tcp fin flag

i've run into a network problem which i cannot solve. on a few computers running windows 8.1 and communicating with linux http server tcp connections dangle on the windows side instead of being ...
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1answer
8k views

What else does “netsh int ip reset” do?

According to this KB article when you run the "netsh int ip reset" command, all it does is to reset the content of two registry keys: SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\ ...
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1answer
1k views

ping -a sometimes returns host name and sometimes returns FQDN. Why? Does this mean DNS is corrupt somehow?

I have a Windows machine called abcd for example and it uses DHCP to receive an IP address (172.28.45.5 for example) When I perform ping -a 172.28.45.5 sometimes I receive abcd as the hostname. ...
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1answer
4k views

Diagnosing packet loss / high latency in Ubuntu

We have a Linux box (Ubuntu 12.04) running Nginx (1.5.2), which acts as a reverse proxy/load balancer to some Tornado and Apache hosts. The upstream servers are physically and logically close (same ...
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340 views

Server with two default gateways won't listen on the second gateway

I am testing a redundant internet connection setup that works like this - I have a network segment, 192.168.80.X It has two gateways - 192.168.80.1 - a FW connected to a frame relay line ...
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2answers
8k views

ESXi network setup for isolated internal virtual machines

Using ESXi v5.1 and vSphere, my networking is setup like so: One standard Switch: vSwitch0 vSwitch0 has one uplink physical adapter (Internet connected) vSwitch0 VM Network has 3 virtual machines ...
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1answer
2k views

Where to find WINS IP address in registry?

I have been writting a powershell script to remotely dump the TCPIP information from the registry of machines in my Windows Domain. I was able to dump the default gateway, subnet mask, DHCP server ...
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1answer
102 views

Need help routing Cisco network- IP routing [closed]

In the above network, can you help me configure routes so the computers on the left can see the computers on the right, and vice versa? I know the syntax of the command is ip route {network ...
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308 views

SSH attempt keeps failing, syn+ack does not reach machine

1 0.000000 10.0.0.1 10.1.1.0 TCP 66 49285 > ssh [SYN] Seq=0 Win=8192 Len=0 MSS=1260 WS=256 SACK_PERM=1 2 0.001160 10.1.1.0 10.0.0.1 TCP 66 ssh > 49285 [SYN, ACK] Seq=0 ...
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1answer
262 views

Do keepalives to socket connections exist?

Pre briefing: Although my question is broad on purpose, I am dealing with nginx connecting to php-fpm (fcgi), which is served via a local socket (/tmp/somesocket.socket). Nginx has a setting to ...
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1answer
371 views

is it possible to use ms loop back adapter to setup local vlan

Is it possible to use Microsoft Loop back adapter to set up Lan connection between two computer which is logically isolated from the main network? 1st computer: has a regular ip stack 192.168.1.x ...
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2answers
2k views

How to globally limit total number of TCP connections with iptables?

I'm having quite a difficult time figuring out how to REJECT both inbound and outbound connections from a machine with iptables once the total number of TCP connections hits a global maximum without ...
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1answer
123 views

Is their an official tool to tweak Windows 2008 server TCP configurations?

We are running scripts that initiates numerous TCP connections and disconnects right away. It's just to test if the remote report is opened and responsive. But we are having random strange issues ...
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1answer
66 views

Random three minute delay for database server connect

we use InterBase on a Windows 2003 server, and in random intervals the client connection to the server takes 180 seconds (three minute) longer than usual. The application does not "hang" with the ...
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61 views

Linux + OpenVPN + SNAT + Failure on client grab the reply to it's own generated traffic

Ok, I'm really desesperate I need to release an openvpn deploy to get rid of a dying server. On the subject: I installed OpenVPN with a routed interface (tun0) into a server with a public IP + 3 ...
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1answer
510 views

Frequent interruptions of SSH connection to VPS

My SSH sessions die at what seem like random times - response will stop, and then a few seconds later PuTTY will pop up a message with, "Server unexpectedly closed network connection." It seems to ...
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2answers
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what is meant by application layer protocols being encapsulated into transport layer protocols? [closed]

I am reading this wikipedia article: http://en.wikipedia.org/wiki/TCP/IP_model#Application_layer It talks about how TCP and UDP are transport layer protocols which are designed to connect one host ...