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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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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votes
6answers
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Is X.Y.Z.0 a valid IP address?
Are IP addresses with a 0 in the last octet valid?
10.6.43.0
In my case, I have the the following netmask
255.255.252.0
What about a 0 for the other octets?
9
votes
5answers
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Huge amount of TIME_WAIT connections says netstat
Okay, this is creeping me out - I see about 1500-2500 of these:
root@wherever:# netstat
Proto Recv-Q Send-Q Local Address Foreign Address State
tcp 0 0 ...
7
votes
6answers
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When IP aliasing how does the OS determine which IP address will be used as source for outbound TCP/IP connections?
I have a server running Ubuntu Server with four IP addresses aliased on a single NIC.
eth0 192.168.1.100
eth0:0 192.168.1.101
eth0:1 192.168.1.102
eth0:2 192.168.1.103
(Using ...
27
votes
8answers
5k views
When/why to start subnetting a network?
Under what conditions does one start to consider subnetting a network?
I'm looking for a few general rules of thumb, or triggers based on measurable metrics that make subnetting something that should ...
26
votes
3answers
13k views
Tuning Linux IP routing parameters — secret_interval and tcp_mem
We had a little failover problem with one of our HAProxy VMs today. When we dug into it, we found this:
Jan 26 07:41:45 haproxy2 kernel: [226818.070059] __ratelimit: 10 callbacks suppressed
Jan 26 ...
30
votes
11answers
16k views
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 ...
17
votes
9answers
7k views
What is the OSI model and how does it apply to todays networks?
As a system administrator what should I know about the OSI model? (Rec X.200)
Briefly, what are the layers and what do they do?
How much do I need to know about in my day-to-day work?
How does this ...
13
votes
9answers
105k views
In Windows, using the command line, how do you check if a port is open?
I want to see if traffic gets through on a specific port on another machine. Is there a simple way to test for this?
12
votes
2answers
3k views
Unix socket vs TCP/IP host:port
Could someone please describe to me the pros and cons of using a Unix socket file vs a tcp/ip localhost:port when setting up services on a server (Ubuntu, FWIW)?
In this particular instance it's for ...
9
votes
2answers
18k 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?
10
votes
2answers
1k views
Multiple IP addresses per NIC
How can I have multiple IP addresses assigned to a single NIC? I remember doing this on Unix way back when. Can it be done on Windows?
6
votes
4answers
3k views
How to automatically assign a route to client in Windows Server PPTP VPN?
Is there a way to configure PPTP VPN on Windows Server which automatically tells the client to add a route for the private network?
I have to do it manually on every PC (once) using following command ...
2
votes
3answers
2k views
Shaping outbound Traffic to Control Download Speeds with Linux
I have a situation where a server makes lots of requests from big webservers all at the same time. Currently, I have not control over the amount of requests or the rate of the requests from the ...
5
votes
2answers
1k views
Answering on the same interface where the request came from
First, I know this is not how IP is intended. But as usual, this is how I need to have it working.
I work for a security company. There are at least 2 network interfaces. Both interfaces should have ...
4
votes
2answers
9k views
UNC Path fails by IP “no network provider accepted the given network path”, but works using hostname
I have an unusual problem with a Windows Server 2003 (Standard x86) box.
It appears the machine will not accept connections to its shares (locally and from other domain member servers) by using its ...
1
vote
3answers
1k views
Too Many ESTABLISHED connection from a single IP address in Apache
netstat -ntp |grep 80 shows too many ESTABLISHED connection from single IP address. Around 300 of them and it is not an attack and user is using a 2G connection to access Apache. This is the case ...
6
votes
1answer
2k views
limits.conf setting doesn't 'stick'
Trying to get the equivalent of ulimit -n 20000 on a high load web server, however the /etc/security/limits.conf on ubuntu hardy doesn't seem to stick.
here is what I set in the config file.
root ...
4
votes
10answers
6k views
Forward port to another Ip/port
I recently found out that my ISP disables port 135. I have a server and personal computer behind my router. A friend and I are working on a programming project and are running into some sql issues ...
29
votes
11answers
5k 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 ...
5
votes
6answers
829 views
Looking for an open source real-time network analysis program
Can somebody recommend an open source real-time network analysis program?
What I'm looking for the program to do is display a graph of bandwidth usage by IP within our internal network that can ...
7
votes
5answers
4k views
How do I view the TCP Send and Receive Queue sizes on Windows?
Linux netstat shows send and receive queue sizes.
How do I get this info under Windows, specifically Server 2003?
4
votes
2answers
6k views
How Can I Harden the TCP/IP Stack in Windows Server 2008?
I would like to make sure that my Windows 2008 servers are hardened against DDOS attacks.
There is a Microsoft Technet article on Hardening the TCP/IP stack, but it was last revised in January 2006. ...
3
votes
2answers
1k views
IIS7 hundreds of connections in CLOSE_WAIT
I have a .Net application on my IIS7 server it was working fine until I had to move it to another server.
I moved the exact same code to the new server and I noticed that after some hours the ...
3
votes
3answers
7k views
Running lsof -i shows a lot of connections in CLOSE_WAIT ? Should I worry
So I am running lsof -i | wc -l periodically and it is telling me that out of 420 lines, between 240 and 255 are in CLOSE_WAIT state. How does TCP connections enter this state ?
Should I be worried ...
2
votes
5answers
9k views
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 ...
3
votes
2answers
2k views
How do I set up IP over FC?
I have 2 systems, with a Broadcom BCM5701 and a LSI7202p, of which are connected with a LC->SC cable. The cards are properly detected in Linux, however I wish to set up IP over FC. I've read online ...
3
votes
3answers
1k views
Are there simpler ways to do traffic shaping in linux besides tc?
I read lartc but I don't feel I need such a complicated solution for simple needs.
One of such simple use cases is to limit a specific process' available bandwidth, upstream or downstream. How can I ...
2
votes
2answers
2k views
How to get a service to listen on port 80 on Windows Server 2003
I've coded a custom windows service that listens on TCP port 80 but when I try to install it on a Windows Server 2003 machine it fails to start because some other service is already listening on that ...
2
votes
4answers
5k views
Ethernet Loopback plug - running a ping
For a project at work, I need to be able to test various Ethernet NICs by connecting them to a "loopback adapter plug", like this one on various embedded Linux boxen that come off a production ...
1
vote
4answers
832 views
Error Connection to SQL Server using [HOSTNAME]\instance or [FQDN]\Instance, [IP]\instance working
This one's kind of weird, at least to me.
I've got MSSQL server 2k5 (STD) installed on Server 2k3 R2 SP2 (on account of some legacy software that doesn't yet support x64 or Server 2008), using ...
1
vote
2answers
2k views
Specifying a preferred route when there are multiple links to same network
I have a server with multiple interfaces and IP addresses on the same network. I would like for non-iSCSI traffic to exclusively use one of the interfaces, and for iSCSI traffic to exclusively use the ...
1
vote
2answers
5k 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 ...
1
vote
2answers
469 views
Static IP for dynamic IP
I have a dynamic IP address. I would like to have a static IP, but Virgin Media don't allow static IPs for residential broadband services, even if you ask them really nicely and offer to pay for it ...
1
vote
1answer
3k views
Windows XP TCP/IP No buffer space available
I have isolated a problem down to this:
On Windows XP Pro, SP2 if one does an experiment where one tries to open TCP/IP sockets in a loop (bascially, listen port 7000, listen port 7001, etc.)
After ...
0
votes
2answers
2k views
Is there a limit to how many sites can be hosted on a single IP address when using HTTP Host Headers on Windows 2008?
For reasons that are lost in the mists of time, our older Windows (2000, 2003) servers have been configured with a "Administrative" IP address and three further "Hosting" IP addresses. There are also ...
