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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What ports are least likely to be probed on the internet? [on hold]

Suppose you've got a server that runs insecure software and you have to make it publicly accessible, what ports are "safest" for providing that service on the internet. By "safest" I mean least likely ...
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0answers
8 views

Many TCP retransmissions with NAT interface in VMware Workstation

I have a problem with TCP retransmissions between outside servers and a virtual machine in VMware Workstation 12 that is configured with a NAT interface (vmnet8). To simulate a slow link, I have set ...
6
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5answers
3k views

Tunnel over UDP or TCP

Is there a way to create something similar to an IPIP or GRE tunnel only over UDP or TCP? I have a GRE tunnel between two servers and I noticed that sometimes it starts to drop packets. At the same ...
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1answer
30 views

Can't communicate out of VM instance for Modbus TCP/IP over port 8080 - routes poosibly required

I have used Google Cloud Developers Console to set up a Windows 2012 Server. I am trying to use this a web server for monitoring hardware utilising Modbus TCP/IP. I have installed a SCADA software ...
2
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2answers
700 views

How to cap network traffic using TCP/IP settings in Windows 7?

Is it possible to cap network traffic on a Windows 7 system so that it will not exceed a given throughput value? The BitTorrent client uTorrent is able to do this, but I am guessing that it's doing ...
2
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2answers
79 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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1answer
48 views

How many data channel ports do I need for an FTPS server running behind NAT?

As the title states, I currently have an FTP server accessible via FTP or FTPS (explicit) running NATed behind a router. The server is running Windows Server 2012 R2 with IIS 8.0 (I believe that is ...
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1answer
1k views

Multiple Homed Windows 2008 Server / Windows 7 Client

I have a small Windows 2008 network, with some Windows 7 clients. The clients are both laptops with docking stations and I would like them to communicate with the Windows 2008 server (for filesharing) ...
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1answer
82 views

Millions of TCP FIN-ACK retransmissions blocking traffic on my desktop machine

In a few minutes I have received about 7 millions(!) FIN-ACK packets from IP address that belongs to Google 74.125.133.188 what totally blocked network traffic on my desktop(!) machine. Other ...
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2answers
107 views

IP on different subnet mask [closed]

I'm still learning the ropes of Windows Server (specifically 2012R2). My assigned task is to setup a static local IP address, I managed to get it set to 192.168.1.96 (with subnet mask 255.255.255.0) ...
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5answers
2k views

how to make standard ssh port a stealth port?

I'm running a personal ssh server on a nonstandard port. If someone tries to log into my ssh server thru the standard port 22, it seems that the server sends "Connection refused" message. $ ssh ...
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1answer
67 views

Static ip addressed hardware unreachable

I need help, I have multiple things (NAS box's and the like) on a static 10.10.10.x network. My new situation forced me to use an Air Card on one laptop and using Internet connection sharing to allow ...
2
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2answers
126 views

TCP sequence number randomization

In a recent interview, my friend was asked about firewalls’ TCP sequence number randomization feature. The interviewer mentioned that we know that a firewall randomizes the TCP sequence number, but an ...
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0answers
16 views

Corrupted files when downloading with HTTP

With my UMTS connection most archives > 50 MB are corrupted when downloading them via HTTP. The problem should not reside in my network, because I have an additional ADSL connection. When I switch to ...
1
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1answer
49 views

Tcp connection breaking, too fast for serial?

I've been having real difficulties getting a tcp connection to work with my web server. I think the issue might have something to do with the speed or ordering of the packets as the connection seems ...
1
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1answer
39 views

When connecting to localhost, does a full SYN, SYN-ACK, ACK handshake still occur?

This question is addressed, primarily for Linux. While I could find the answer myself, I'm hoping someone out there just knows the answer implicitly and can save me some time. If I'm connecting to a ...
2
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0answers
520 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 ...
36
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12answers
11k views

Why would you use IPv6 internally?

Of course, I realize the need to go to IPv6 out on the open Internet since we are running out of addresses, but I really don't understand why there is any need to use it on an internal network. I have ...
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0answers
49 views

What should happen when receiving an ICMP Fragmentation Needed message?

In general, and in particular on a Solaris 10 machine ... See, we are having an issue in our network. I handle some reverse proxy instances on a Solaris 10 server that is behind a load balancer, and ...
1
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2answers
91 views

Can I add a static route to a VPN network if the default gateway IP is dynamic? (Windows 7)

Can I add a static route to a VPN network if the default gateway IP is dynamic? (Windows 7) This is easy to solve with a permanent route if the default gateway does not change as you can do this: ...
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1answer
77 views

Why is wireshark capturing packets not destined to my host? [closed]

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 ...
2
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3answers
13k views

Serial port forwarding over TCP/IP (linux server)

I am looking for a way to use a remote serial port on a linux machine over LAN. The machine is running ubuntu 10.04 and I have a arduino board connected to it, that I would like to be able to ...
2
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0answers
159 views

Does a ping to 127.0.0.1 hit the network card? Which RFC / standard states that? [closed]

I recently did an exam where one of the questions stated that you can run ping 127.0.0.1 on a computer to verify if its network card is working. I have already read on multiple sources that this ...
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2answers
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What do all the settings in the Advanced TCP/IP Properties DNS Tab Mean?

Can someone explain TCT/IP > Properties > Advanced > 'DNS' tab please? I know what DNS, primary DNS suffix and DNS suffix are, but this tab has some confusing properties.
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1answer
97 views

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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5answers
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How to extend IP Range from 192.168.1.1 to 192.168.2.254

Here's my question. I currently have a network setup to have Static IP manually assigned between 192.168.1.1 and 192.168.1.99 and the rest (192.168.1.100 through 192.168.1.254) assigned automatically ...
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2answers
54 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 ...
288
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6answers
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How does IPv4 Subnetting Work?

This is a Canonical Question about IPv4 Subnets. Related: How does IPv6 subnetting work and how does it differ from IPv4 subnetting? How does Subnetting Work, and How do you do it ...
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2answers
2k 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 ...
4
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1answer
180 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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1answer
811 views

Big IP orphaned connections

Let me state up-front that I know just enough about networking at this level to be dangerous, so if I say something stupid, please be kind. I am using a Big IP load balancer in front of 3 Apache ...
13
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3answers
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How are IP addresses actually assigned?

I'm having a hard time understanding how a governing body assigns IP addresses, companies use BGP to advertise those IPs, and how the internet works. Then, where the hell does DNS come in? Can ...
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1answer
668 views

How to debug why WAN TCP/IP throughput is lower than expected?

I'm trying to figure out why tcp/ip throughput between two hosts I control is much lower than expected. Host A: internet connectivity provided by Comcast (Residential) in Boston Metro -- can ...
14
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4answers
58k views

Which is the default TCP connect timeout in Windows?

Which is the default TCP connect timeout in Windows? There is a registry key to configure it or it's set dynamically?
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1answer
41 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, ...
5
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2answers
3k views

Unable to increase the dynamic port range on Windows Server 2008

I'm trying to "tune" the TCP/IP stack on some Windows Server 2008 machines by following the instructions here: ...
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1answer
116 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 ...
2
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2answers
1k views

Checkpoint dropping traffic

I have R65 installed on Solaris 9, on Sun4u. It's currently running into an issue where during long connections (I think. It doesn't appear to do this to all connections, and I can't work out what the ...
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2answers
145 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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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 - ...
8
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1answer
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What is the maximum number of TCP connections I can have in Windows Server 2008?

I would like to have as many connections (single connections from many different clients) as humanly possible in a server running on Windows Server 2008, in order to support a Comet-style application. ...
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1answer
441 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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1answer
1k views

Determing MSS value on Windows Server

In this Technet article about the MSS limitations of Windows Server 2008, it mentions: After analyzing the network trace collected on the source Windows 2008 Server, we found out that the remote ...
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1answer
143 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 ...
3
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4answers
4k views

Windows 7 DHCP Default Gateway not Overridden by manual Default Gateway

We have recently installed Windows 7 for student computers. All student computers must be routed through our content filter which is located at 192.168.0.63. This was done in WinXP by adding a Default ...
13
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4answers
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What does a DNS request look like?

I have seen what the text representation of an HTTP request is, but what does a DNS request look like? Where in the data is the location of the URL you are trying to locate? Also, how is the ...
36
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11answers
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What is the difference between UDP and TCP?

My router has two protocols (and a "both" option) that I can select when setting up port forwarding: UDP and TCP. What is the difference between these two protocols and when would you select one over ...
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0answers
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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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5answers
876 views

Is it possible to configure Nginx to send TCP keepalive?

On TCP connections held by NGinx, can it be configured to send TCP Keepalive (Not HTTP KeepAlive!)
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3answers
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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, ...