Questions tagged [networking]
Networking refers to the technologies and techniques that enable the interconnection of devices and applications allowing them to communicate electronically.
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How do you avoid network conflict with VPN internal networks?
While there's a wide variety of private non-routable networks across 192.168/16 or even 10/8, sometimes in being thoughtful of potential conflict, it still occurs. For example, I set up an ...
38
votes
6
answers
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Bridging wlan0 to eth0
On Arch Linux, I would like to have eth0 (connected to bridged router) share the connection received from wlan0, I've read tutorials but I'm not command savvy as other users are and don't completely ...
37
votes
8
answers
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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 ...
37
votes
6
answers
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Hardware Firewall Vs. Software Firewall (IP Tables, RHEL)
My hosting company says IPTables is useless and doesn't provide any protection. Is this a lie?
TL;DR
I have two, co-located servers. Yesterday my DC company contacted me to tell me that because I'm ...
34
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8
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What is the network address (x.x.x.0) used for? [duplicate]
It appears to be common practice to not use the first address in a subnet, that is the IP 192.168.0.0/24, or a more exotic example would be 172.20.20.64/29.
The ipcalc tool I frequently use follows ...
31
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14
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How can I display the IP address of an interface?
If I want to display the IP address that is assigned to eth1, how can I do this in Bash?
31
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2
answers
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Under what circumstances is TCP-over-TCP performing significantly worse than TCP alone (2014)?
Many admins keep perpetuating - on ServerFault and elsewhere - how bad of an idea TCP-over-TCP is, e.g. in VPNs. That even the slightest packet loss will make one suffer from at least severe ...
31
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6
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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 (...
30
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1
answer
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MySQL [Warning] IP address could not be resolved
I'm running MySQL5.6.3 on a CentOS 6.1 virtual machine running on Windows XP in VirtualBox.
The network card is configured in bridge mode, so my physical & virtual machines share the same ...
24
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7
answers
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Why don't more organizations use inside-to-inside NAT or similar solutions to allow NAT hairpins?
Inside-to-inside NAT aka NAT loopback solves hairpin NAT issues when accessing a web server on the external interface of an ASA or similar device from computers on the internal interface. This ...
21
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7
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Troubleshooting a "slow" network
We've all had a complaint that the "network" is "slow" at some point: might be localized to one room (switch) or one computer, might just be Internet (DNS? Browser issue?), might be just one ...
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4
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Unable to Share Data between Amazon EC2 Instances for Windows
I have two Amazon EC2 Instances running Windows Server 2003 and IIS 6.0.
Both the instances are created in the same region and have the same Security Group.
I enables icmp for all ports and connection ...
20
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2
answers
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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 ...
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6
answers
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How does geography affect network latency?
I have the option of hosting our database/web server at a managed hosting company on the East Coast (US) or one on the West Coast (US). Our company is based out of New York City, and both hosting ...
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5
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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 ...
18
votes
5
answers
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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 ...
18
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4
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Disable TCP-Offloading {completely, generically and easily}
I want to disable tcp-offloading (TOE) on my Debian servers. I would use something like:
ethtool -K …
I have some wishes, though: is it possible to integrate it cleanly into Debian?
This reads: no rc....
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4
answers
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Best way to segment traffic, VLAN or subnet?
We have a medium-sized network of around 200 nodes and are currently in the process of replacing old daisy-chained switches with stack-able or chassis style switches.
Right now, our network is broken ...
13
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4
answers
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Link bonding across multiple switches?
I've read up a little bit on bonding nics with ifenslave; what I'm having trouble understanding is whether there is special configuration needed in order to split the bonds across two switches. For ...
12
votes
2
answers
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How to ignore a set of Mac addresses in dhcpd.conf?
Is it possible in dhcpd.conf to ignore requests from a set of MAC addresses?
Something like this:
host vminstances {
hardware ethernet d0:0d:*;
ignore booting;
}
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3
answers
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How do I get anycast for my servers?
I want to have anycast for my web service, but I cannot find any information on how to achieve this or any company that can help.
I've found loads of companies offering anycast DNS, but that's not ...
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9
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Network monitoring [duplicate]
Possible Duplicate:
What tool do you use to monitor your servers?
What software would you recommend to monitor a network? We have a main server which acts as a DNS among other services. And we ...
8
votes
5
answers
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Unable to Telnet into port 25 on CentOS PostFix Server
I'm trying to telnet into port 25 on a CentOS server that runs PostFix to test sending email messages from the server.
When I try to telnet in from another CentOS box on the same network I get the ...
8
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2
answers
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Can't ping multihomed Linux machine on non-default interface
I have a multihomed Ubuntu server with a set of interfaces that includes:
eth2: 10.10.0.131/24
eth3: 10.20.0.2/24
The default interface is eth2, with a gateway of 10.10.0.1. Here's what the routing ...
8
votes
2
answers
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KB 4480970 and or KB 4480960 breaks SMB2 connections to Windows 7 shares
It's become clear that last night's (Tues Jan 8th 2019) patches to Windows 7 broke SMB2 networking in Lanman Server.
One or both of KB 4480970 and KB 4480960 results in any OS that uses SMB2 (such as ...
6
votes
3
answers
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DHCP server for multilple VLANs [duplicate]
Possible Duplicate:
Can I have multiple DHCP servers on one network?
This is a very old question i guess.In this forum itself it has been answered in Multiple VLANs, multiple subnets, single DHCP ...
6
votes
1
answer
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host port forward with qemu through libvirt in user-mode networking
I'm having trouble editing my libvirt's host-xml to make qemu forward TCP connections to the guest. This questions linked to a blog post which recommended adding -redir to the Qemu command line. But ...
6
votes
3
answers
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How to set up two default routes in linux
TL;DR
How to set up two default routes in linux (corresponding to two interfaces), such that incoming traffic from both interfaces is accepted.
Scenario
I have a host having two NICs eth0 and eth1....
5
votes
3
answers
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How to request/acquire all records from a DNS?
I want to see what nodes exist under a certain domain from within the domain. Short of querying every valid IP address within that domain, is there a way to get all records/map the network?
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How do I force all devices on a network to register with IT before connecting, without vulnerability to Static IP-ing or MAC spoofing?
Context:
I'm an admin for a midsize corporate network with several overlapping wireless access points and an ethernet cabling infrastructure. To comply with a security audit, we were recently ordered ...
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vote
5
answers
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vSwitch configuration with 12 uplinks
I have been doing a lot of research on vSwitch configurations, but I think I am more confused now after all of the reading that I have done. So here is my situation 3 ESX Hosts (12 nics each), 1 ...
1
vote
1
answer
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iptables PREROUTING not in effect
We are running a ubuntu 20.04 in AWS. We are trying to set up an iptables rule so any MySQL traffic with a dummy IP address will be forwarded to the MySql database at 172.31.6.173 in the same VPC. Let ...
0
votes
2
answers
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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?
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4
answers
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How to check if a port is blocked on a Windows machine?
On the Windows platform, what native options to I have to check if a port (3306, for example) on my local machine (as in localhost), is being blocked?
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5
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What is this IP address: 169.254.169.254?
I have always noticed an IP something "169.254.x.x" in my routing table even when I am not connected to any network in my Windows operating system.
In Linux, when I list my routing table.
$ ...
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votes
6
answers
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SSHFS mount that survives disconnect
I'm using SSHFS mounts from my laptop to a central server.
Obviously, the SSHFS mount is broken after a longer disconnect (eg. during suspend), cause the underlying SSH connection timed out.
Is ...
90
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17
answers
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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 ...
79
votes
14
answers
230k
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Docker containers can't resolve DNS on Ubuntu 14.04 Desktop Host
I'm running into a problem with my Docker containers on Ubuntu 14.04 LTS.
Docker worked fine for two days, and then suddenly I lost all network connectivity inside my containers. The error output ...
70
votes
4
answers
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What is the "slash" after the IP? [duplicate]
In Amazon EC2, where I set "security groups", It says: Source:
0.0.0.0/0
And then it gives an example of: 192.168.2.0/24
What is "/24"?
I know what port and IP is.
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votes
6
answers
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What is the difference between a managed and unmanaged switch?
I've seen some documentation discussing the use of an unmanaged switch. What is the difference in functionality/performance/etc. between an unmanaged and managed switch?
65
votes
6
answers
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Why do ethernet cables have 8 wires?
This might seem a stupid question but why do Ethernet cables have 8 wires? Cat5 cables were just using 4 of the 8 wires, so only 4 are actualy 'needed'. Why not 12 or 16 wires?
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6
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iptables error: unknown option --dport
The command iptables no longer recognizes one of the most commonly used options when defining rules: --dport.
I get this error:
[root@dragonweyr /home/calyodelphi]# iptables -A INPUT --dport 7777 -j ...
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2
answers
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When do DNS queries use TCP instead of UDP? [duplicate]
Possible Duplicate:
Is it true that a nameserver have to answer queries over TCP?
I know DNS uses UDP for most of its queries, but in what circumstances will it use TCP instead?
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votes
5
answers
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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 ...
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11
answers
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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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5
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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.
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5
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Can TCP and UDP packets be split into pieces?
Can TCP packets arrive to receiver by pieces?
For example, if I send 20 bytes using TCP protocol, can I be 100% sure that I will receive exactly 20 bytes at once, not 10 bytes then another 10 bytes ...
43
votes
3
answers
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What is the command to flash a NIC link light?
I remember using a command line tool to flash a NIC's link light to identify it. I can't remember for the life of me what it was.
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curl (56) Recv failure: Connection reset by peer - when hitting docker container [closed]
From an AWS ec2 instance (which runs docker), I am trying to curl my docker container-hosted web service.
Given:
[ec2-user]$ docker ps
CONTAINER ID IMAGE ...
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1
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How can e-mail be delivered to a domain without an MX record?
Somebody has 2 e-mail addresses: [email protected] and [email protected] . The DNS records for these domains look like this:
domainname.com.br
$ dig any domainname.com.br
;; ANSWER SECTION:
...