Networking refers to the technologies and techniques that enable the interconnection of devices and applications allowing them to communicate electronically.

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3answers
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second ip address on the same interface but on a different subnet

Is it possible in CentOS 5.7 64bit to have a second IP address on one interface (eg. eth0) - alias interface configuration - in a different subnet? Here is the original config for eth0 more ...
3
votes
2answers
817 views

Reserve a single ip for a wired and wireless NIC of the same machine

I'm using w2k3 dhcp server, and I've reserved an IP adress for my laptop to facilitate port forwarding. I previously had a pure wired network, but I just added a WiFi router to this network for the ...
0
votes
2answers
622 views

is it possible to direct connect a client and server with 10GBASE CX4 copper cables?

Server has two 10GBASE-CX4 ports. client has 10GBASE CX4 HBA. can theybe directly connected with a CX4 cable without the need for a switch? like SAS Infiband connectors?
70
votes
17answers
27k views

Should network hardware be set to “autonegotiate” speeds or fixed speeds?

We recently had a little problem with networking where multiple servers would intermittently lose network connectivity in a fairly painful-to-resolve way (required hard reboot). This has been going on ...
29
votes
3answers
18k views

What's best practice for communication between Amazon EC2 instances?

I've been setting up Amazon EC2 instances for an upcoming project. They are all micro instances, running Ubuntu Server 64bit. Here's what I've setup so far: Web Server -- Apache Database Server ...
39
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5answers
2k views

Is there a linux terminal command that lets you see the amount of data coming in to your tcp connections in real time?

It would be something similar to top, where you see your cpu processes in real time. I'm not looking for a GUI like Wireshark to do it.
20
votes
4answers
10k views

Why do people tell me not to use VLANs for security?

As per title, why do people tell me not to use VLANs for security purposes? I have a network, where a have a couple of VLANS. There is a firewall between the 2 VLANs. I am using HP Procurve switches ...
28
votes
8answers
7k 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 ...
40
votes
4answers
15k views

How exactly & specifically does layer 3 LACP destination address hashing work?

Based on an earlier question over a year ago (Multiplexed 1 Gbps Ethernet?), I went off and setup a new rack with a new ISP with LACP links all over the place. We need this because we have individual ...
13
votes
3answers
15k views

How to use Bonjour?

First, what exactly Bonjour does (pleas read my guesses written bellow)? Here I found out that Bonjour enables automatic discovery of computers, devices, and services on IP networks. But I thought ...
29
votes
8answers
26k views

Windows Server 2008 R2 network adapter stops working, requires hard reboot

TL;DR version: Turns out this was a deep Broadcom networking bug in Windows Server 2008 R2. Replacing with Intel hardware fixed it. We don't use Broadcom hardware any more. Ever. We have been ...
21
votes
5answers
150k 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?
19
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4answers
2k views

Slow Transfers over Distance

From our NY Datacenter, transfers to locations that are farther away are having poor performance. Using speed test to test various locations, we can saturate our 100 mbit uplink to Boston and ...
13
votes
7answers
14k views

traceroute TCP equivalent for Windows [closed]

I'm trying to determine where connectivity to an external host using a specific TCP port is being blocked. Traceroute for Windows only uses ICMP, and telnet will only tell me that the port is blocked ...
5
votes
4answers
1k views

Traffic Management recommendations [closed]

What's your strategy towards traffic prioritization/management. I am not really to just get a list of packet shaping solutions. Instead, I would like to get recommendations about traffic management ...
11
votes
6answers
11k views

How to tell if it's your problem or your ISP's problem

I originally titled this "how to tell if your internet is down or your network is just screwed up" and Jeff's AI said that this questioned would probably be closed. Nevertheless, someone here is ...
8
votes
2answers
16k views

Bridging wlan0 to eth0

On arch Linux, I would like to mainly have eth0 (connected to bridged router) share the connection recieved from wlan0, Ive read tutorials but I'm not command sabby as other users are and don't ...
11
votes
2answers
2k views

VMware Distributed vSwitches (VDS) - Design, theory, *real* use cases and examples?

I'm starting to explore VMware Distributed Switches (dvSwitches or VDS) for use in existing and new installations. Assume VMware version 5.1 and newer with Enterprise Plus licensing. Prior to this, ...
18
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9answers
10k 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 ...
17
votes
2answers
828 views

Are there any advantages to using someone else's publicly-routable IPv4 addresses locally?

My 10000+ users network, which spans the whole State and is very complex, has a "strange" addressing scheme. Though our PCs are not directly connected/exposed to the Internet, our network designers ...
11
votes
3answers
4k views

Networking Units: Not getting expected performance from 100Mb Ethernet

Our company has a brand new NAS, and the idea is that we will be able to use it for fast, shared access to our data on our network. It's a fairly simple 2-disk system, but from what I understand, it ...
5
votes
4answers
42k views

How to route different traffic thru different network interfaces (in Windows)

I've searched for details on how to do this but I've been unsuccessful - I wondered if someone could offer up some advice. So, let's say I have 2 network cards (LAN and 3G in my instance), both ...
4
votes
6answers
1k views

Encrypting absolutely everything, even within the LAN

Has anybody tried that approach already? I'm really considering it: Instead of relying on network based IDS etc., every packet must use encryption which was initiated by a certificate issued by my own ...
11
votes
7answers
463 views

Truly understanding networking?

I understand the basics of networking such as Lan and stuff. I know what many of the protocols are and how to build a client/server socket program in C. But what I really want is a very good ...
9
votes
2answers
833 views

linux command to prevent dos attack by using netstat and iptables

I want to DROP more than 200 requests per ip to prevent ddos attack. this is command that i used to detect requests count per ip : netstat -alpn | grep :80 | awk '{print $5}' |awk -F: '{print ...
21
votes
4answers
1k views

1 Year DHCP Lease

Just a little background I'm a fairly young I.T. Tech working in a school only and only been working in the as a technician for a few years so I would still consider myself a "newbie" Anyway, My boss ...
13
votes
4answers
4k views

Hardware firewall vs VMware firewall appliance

We have a debate in our office going on whether it's necessary to get a hardware firewall or set up a virtual one on our VMWare cluster. Our environment consists of 3 server nodes (16 cores w/ 64 GB ...
13
votes
4answers
22k views

Is there a way to get wireshark to capture packets sent from/to localhost on Windows?

Is there a way to get wireshark to capture packets sent from/to localhost? When I monitor traffic going from my computer to another, or from another computer to my computer, then it works. But ...
8
votes
1answer
7k views

What exactly is the MTU/MRU issue, what it is caused by and how to fix it?

In cases of hanging, freezing, slow, unresponsive internet connections the cause is usually unreasonably identified as "MTU/MRU issue" with several hastily proposed "magic cures" (usually invalid or ...
6
votes
3answers
19k views

How do I force specific permissions for new files/folders on Linux file server?

I'm having an issue with my install of Ubuntu 9.10 (file server) and its samba permissions. Logging in and reading works fine. However, creation of new directories by users restricts access for other ...
5
votes
2answers
7k views

Bridging LXC containers to host eth0 so they can have a public IP

UPDATE: I found the solution there: http://www.linuxfoundation.org/collaborate/workgroups/networking/bridge#No_traffic_gets_trough_.28except_ARP_and_STP.29 # cd /proc/sys/net/bridge # ls ...
5
votes
3answers
7k views

Defining a persistent static route on Mac OS X

How does one define a static route on MacOS X which persists through reboots? The only suggestion I've found on Google advises setting up a launchd service to run at boot, which seems like a horrible ...
3
votes
5answers
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Network port open, but no process attached?

I have a weird situation going on with an open network port. My main question is, why would there not be a program associated with an open TCP port: netstat -ln --program Active Internet connections ...
2
votes
2answers
7k views

how to forward wlan0 to eth0?

I get internet from my wireless wlan0 and I would like to forward it to eth0 which is connected to another laptop. How can I do that? Thanks. Edit: my wireless card is intel: 0b:00.0 Network ...
11
votes
2answers
15k views

How do I clear the interface stats on Linux

So one of my clients configured one of their switches and the resulting configuration resulted in a duplex mismatch between the switch and a Linux host. We have fixed the duplex mismatch, but is ...
11
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
4k 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 ...
5
votes
4answers
1k views

Best way to improve resilience?

One of the major projects I have lined up for 2010 is attempting to mitigate some of the Single Point of Failures (SPOFs) in a network I currently manage. We currently have a single datacentre rack ...
4
votes
6answers
7k views

Regular user using ports below 1024 [duplicate]

Is there a way on Linux (CentOS if that matters) to enable regular users to use ports below 1024? (open listening TCP socket on that port) Currently I understand that only root has privileges to use ...
2
votes
3answers
2k views

multiple physical interfaces with IPs on the same subnet

I have a linux box with 9 NICs on it, and I want eight of them to have unique addresses on the same subnet, e.g.: ifconfig eth1 192.168.123.1 netmask 255.255.0.0 ifconfig eth2 192.168.123.2 netmask ...
2
votes
3answers
10k views

Conditional DNS forwarding with named on Linux

I have a Centos 5.2 server which runs named for DNS resolution - it doesn't hold any information of its own, and just forwards all requests. From the named.conf: options { [...] forwarders ...
2
votes
4answers
237 views

Diagnose Network Faults

Disclaimer: I am a developer, not a system admin, please be gentle. Where I work we are having a lot of intermittent network problems. Sometimes the DNS will fail, but access to servers can be done ...
1
vote
3answers
1k views

I am on Rackspace Cloud. What is Bandwidth Out and Bandwidth In?

Can someone give me very easy to understand examples? And how to calculate? Suppose someone views a page off of my web server. This page is 400kb. How much is the bandwidth in and out for me?
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vote
2answers
2k views

Bonding Nics with Linux to get better performance

I am trying to bond two nics together to get better performance. I have two 1000MBps Intel Nics. When I had one nic I was running some benchmarks getting 106 MB/s. This is pretty close to 1GBps. So I ...
12
votes
2answers
449 views

Two identical fiber optic broadband lines working as one

I am looking for a way I could combine two 100Mbit fiber optic lines into a single connection for our office. I assume it involves some Cisco learning or something similar. Do I need to configure ...
10
votes
6answers
16k views

Why was my ping answered by a different IP address than the one pinged?

While trying to setup a MSSQL clustering solution, I am running into a problem that is outside of my expertise that is related to networking. I was trying to find a free IP to used for my node. I ...
6
votes
7answers
3k views

Local or public NTP servers?

For a relatively large network (thousands of hosts) - what are the arguments for and against running a locally managed (pool of) NTP server(s) (perhaps periodically set via some public NTP server) and ...
6
votes
6answers
2k views

Windows 2008 Server on mixed ethernet speeds — download from share slow, but fast plain TCP

I have a Windows Server 2008 R2 x64 server that is AD controller and file server. I have a problem that Windows XP clients experience terribly slow (less than 10Mbps, really less than ...
5
votes
2answers
2k 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
1k views

Network Redundancy Example

Looking for help filling in how redundancy in the following model might work: I believe my Datacenter will give me redundant gateways with two hand offs (going to have to talk to the more about ...