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

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1answer
48 views

Simplex, half-duplex, full-duplex (ccent1)

If simplex, half and full duplex are OSI layer 5 (session layer) modes, why are they configurable on a l2 switch?
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26 views

Benchmark network (internet) connection on server

I have a dedicated ubuntu server I rentet. Now I'm running a lot of ruby background processing on that server, that - among other things - does a lot of get requests to very small images (about 10kb) ...
0
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55 views

TCP ignores some packets for no reason

I have a weird problem which I can't understand. The actual network configuration is quite complex, because I am using Openstack and Docker to build a virtual network. However, the problem is not ...
1
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1answer
97 views

CentOS with multiple NIC and static route

I am trying to setup a CentOS with 3 NIC and static routes. eth0 has IP address 192.168.10.2 and GW:192.168.10.1, eth1 has IP address 192.168.20.2 and GW:192.168.20.1, eth2 has IP address ...
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0answers
31 views

Xen VM could not be installed

I have rented a server from Hetzner. I have installed Xen on Dom 0 - Centos 6.5. I couldn't create a Dom1 Centos 6.5 VM. The Error I see is 'Unable to retrieve 'the link for centos image' while ...
3
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0answers
99 views

TCP connection stuck in SYN_RECV state despite ACK received

My client and server are both internal machines. tcpdump on both client and server show all three parts of handshake are communicated, however netstat on server shows SYN_RECV, and on client shows ...
0
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1answer
57 views

Monitoring “external” worm activity remotely

Some of our computers in our company has been infected with the worm Conficker. We don't know the source of the infection, but I want to monitoring the outside activity to see if we are still infected ...
0
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2answers
84 views

How to check current TCP Congestion Window on Linux?

Does anyone know how to check the current value of initcwnd? (particularly on Debian [Squeeze]) I've searched, but can't find a definitive answer to this. I haven't changed it, but may want to ...
32
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1answer
903 views

Random TCP RST's on certain websites, what's going on?

Short version: One Windows Server 2012 machine on my network is getting persistent but intermittent TCP RSTs when connecting to certain websites. Dunno where they're coming from. Check out the ...
0
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2answers
86 views

bridging LXC containers to host network with different IP range

I'm pretty new to linux, and I have been struggling with a problem for the past week or so... I am trying to setup a cluster of LXC containers on a workstation (host) which is has IP 192.168.10.33 ...
0
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0answers
34 views

Automatically configure networking on new VM in XenServer

We have a base RHEL 6.5 64-bit template that we use to create new VMs in XenServer. Every time we make one, we have to configure: /etc/hosts /etc/sysconfig/network ...
0
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2answers
100 views

Recommended TCP keepalive settings for a busy server

We are having some network timeout issues on a Debian server that is quite busy, and maintains multiple connections to a number of other servers on the network. Here are our current TCP keepalive ...
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1answer
23 views

Access 2 Hosts from Internet on same subnet [closed]

Hi I have 2 raspberry PI in my network. And I want both of them accessibles from the internet. Right now I have a DMZ from you can access one with NO-IP setup: www.blabla.no-ip.org ----->DMZ ...
4
votes
1answer
133 views

Batch configure HP ILO from laptop

I need a method of setting over a thousand Ilo's on our HP DL360p Gen 8 servers (With hundreds more on the way!) Our environment doesn't allow for the use of any automatically assigned address such ...
0
votes
1answer
71 views

2x uplinks in HSRP - how to setup switch?

Our ISP provides us with 2x 10G uplinks, and they use HSRP on their end. We see incoming traffic (load balanced) on both ports, but outgoing from us is only via one port. We only run L2 on our side ...
0
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0answers
104 views

Only allow SSH from specific IP to evade VPN connection?

I want a Linux server to use the VPN connection for all traffic that is not SSH from a specific IP. If the VPN connection becomes unavailable, not other communication than SSH with the specific IP ...
0
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0answers
91 views

Secondary DPM server and access to protection agents at primary server

Disclaimer: This is not an ideal setup. In a perfect world we would have a direct two-way VPN between our site and the remote site. My task is to enlighten the consequences of running a System Center ...
2
votes
3answers
161 views

Why is cat6 required for long cable runs?

I'm glancing over a Ubuiquiti airFiber radio starter guide and it says "outdoor shielded 5e or above cabling should be used for all wired Ethernet connections. Category 6 is required for ...
0
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1answer
37 views

Routing particular service over vpn

Running Ubuntu 14.04 LTS. I need to connect to a SMB share that isn't local. The only way I can connect to it is over a VPN. The particular VPN service is Juniper. Connecting to the VPN is easy and ...
0
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1answer
55 views

Do blocking input ports increases security?

1-Do blocking unused input ports in firewall increases system security? How? (as there is no daemon listening on those ports anyway) 2-Do dropping those unused ports will positively or negatively ...
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1answer
45 views

Debugging slow network [closed]

I've been tasked with debugging why my company's network connection is running slow. Having no previous experience in this field I have absolutely no clue where to begin or what tools to use. The ...
1
vote
2answers
44 views

Why isn't my static route applying?

I'm migrating one of my services to a new public facing IP and I'm at a loss as to why the recently added route isn't functioning. This is a Server 2008 R2 box. I've covered several other questions - ...
0
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0answers
21 views

How to meet the arp table and the network toology with wireshark

I'm wondering if is possible meet(see) the arp table in a network traffic with wireshark or find some way to build manually the arp table, and how to see the router and swiches of topology( for ...
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votes
1answer
45 views

What type of switch should I get to implement a site with around 140 desktop machines, plus around 20 SIP phones? [closed]

We're moving to a new office and we will be needing to setup a network closet. I'm estimating that we will have around 140 ethernet ports and will be using CAT6a cabling for 1Gbps connections. I'm ...
0
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0answers
43 views

Linux: routing within 2 internal networks

We have a network that contains one gateway server with 3 network interfaces: eth0: (global IP) eth1: (internal IP 192.168.0.0/24) ib0: (internal IP 10.2.2.0/24) The other servers in the network ...
0
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1answer
81 views

Apache + mod_ssl (on Vagrant) HTTP connection works fine, HTTPS connection times out

Introduction Hi guys, this is quite a strange one that I've been battling with for a few hours now. I have a CentOS Vagrant box with a network adapter attached to my NAT (as opposed to host only). I ...
1
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1answer
110 views

Is it possible to use listening socket for initiating client connection?

Today I noticed such a situation: [root@cwf-hmaster.staging-scp ~]#netstat -taupen | grep 54310 tcp 0 0 ::ffff:10.0.12.209:54310 ::ffff:10.0.12.209:54310 TIME_WAIT 0 0 ...
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2answers
53 views

TCP/UDP Small Package Size optimization [closed]

I currently have the problem, that when a LOT of RTP streams (>800) go to one server the max. speed is onlynabout 70-80 Mbit (on a Gigabit LAN - all Hardware components are Gigabit components) 130 ...
1
vote
1answer
47 views

iptables destination NAT from one range to another

I am trying to make destination NAT from one range (192.168.2.0/24) to corresponding ip addresses in another range (192.168.1.0/24). I have managed to do this ip by ip iptables -t nat -A PREROUTING ...
0
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1answer
37 views

Don't connect to OpenVPN when on internal network

We have an OpenVPN server - it's physically running in our internal subnet. Basically the when the VPN client connects, he gets an IP from the VPN's subnet and a route to the internal subnet is pushed ...
-6
votes
1answer
41 views

encryption of fiber communications [closed]

We have to connect one site to another using leased fiber ( theoretically it's a dark one ) in order to replace a radio link. All servers are in one site. Both location now have Gigabit networks. Can ...
0
votes
1answer
32 views

Dynamic port forwarding reports connection failed and timeout

I'm running a benchmark based on selenium to send requests to an application server. Since the application server is deployed on a private cloud, I'm not able to connect to the server from the ...
-1
votes
1answer
84 views

F5 BigIP limiting the amount of sources able to connect to a virtual server

In an F5 bigIP LTM with sw version 11.4.1, is it possible to have multiple sources addresses for a virtual server? The objective is to limit the number of sources from where the virtual server can be ...
1
vote
1answer
46 views

Can't access KVM Host (network brige)

I have a strange problem since I rebooted my KVM Host running CentOS 7. I have a network bridge which was going fine, I could access my KVM hosts and guests, but since reboot, I can't access the ...
1
vote
0answers
27 views

Dell PE2900 seeing only 1/2 ethernet controller

I have 2 ethernet controller on my dell poweredge 2900 : http://www.dell.com/downloads/emea/products/pedge/en/pe2900_Spec_Sheet_Quad.pdf But I only see one on my linux system : $ ip addr 1: lo: ...
0
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0answers
17 views

Using a Barracuda F400 Firewall Router Without a Modem

I'm looking into a problem where VoIP phones don't ring for some of the incoming calls that I believe might be due to the network configuration. Do you need a modem if you are using a Barracuda F400 ...
1
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0answers
109 views

How to create a link between GNS3 and a VMWare Workstation VM that is totally isolated from the physical host?

My physical host machine runs windows server 2012 R2 with a DHCP server. I have the following topology in GNS3: Windows Server is the physical machine, it is connected to both VMNet 2 and VMNet 3 ...
5
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0answers
103 views

POST of MTU + ~798 bytes gets lost

I have a very weird issue with certain packets not arriving on the destination host. It happens when we transmit a POST that is somewhat larger than the MTU. We can reproduce it with this script: ...
0
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0answers
56 views

Solaris 10 inside KVM (Ubuntu 14.04) - network card not working

I have a problem with getting network running on a Solaris 10 guest running on a Ubuntu 14.04 kvm host. Installation of the guest runs fine but I can get no network connectivity from the guest to the ...
3
votes
1answer
31 views

Windows Server to Server copy, executed remotely, process overview

Ok so I've got 3 servers in this example Server_A, Server_B, Server_C I want to move data over the network from Server_A to Server_B by executing a batch script on Server_C, it would be something ...
2
votes
0answers
41 views

Which openstack instance has a certain IP address

There are IPs on my network that are not configured as fixed or floating in Neutron, they are simply claimed by an instance (e.g. via ifconfig eth0:1 ip.add.re.ss). How do I get openstack (possibly ...
0
votes
1answer
44 views

What better solution to adopt for client server system implementation by java sockets

I need some advice from someone experienced in networking. I have already created a system designed to monitor some tasks (5-30) that are written in java started by a auomatic scheduler or by ...
-1
votes
1answer
51 views

what ports are used for files transfer in the lan?

when I'm using Ethernet LAN....many things you can do on the LAN, one of them is to transfer files between computers after sharing the files.....the question is : what ports are used for files ...
0
votes
1answer
66 views

Set gateway for specific ip destination and port

I have two internet connections. One has a static public ip address (WAN-STATIC gateway ip 10.0.0.1) and the other has a dynamic public ip address (WAN-DYNAMIC gateway ip 10.0.0.254). I wish to force ...
-1
votes
1answer
31 views

Geo distributed ip [duplicate]

When i ping 8.8.8.8 from my home computer (europe) i get around 26 ms latency. When i ping 8.8.8.8 from a server(US) i get around 1 ms latency. When i ping my (US) server from home (europe) i have 130 ...
2
votes
2answers
70 views

Running own DNS in intranet, how to reach outside DNS from clients

The Scenario: I am creating a Network for 8 Windows 7 Workstations running in a Student Laboratory. They are supposed to browse the internet, but not to be reached from outside their intranet. To ...
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votes
1answer
75 views

What should an Ops person know about hardware for an interview? [closed]

It is easy to find typical interview questions for sysadmins and network engineers, but when I search for hardware engineer (hardware operations engineer) I can't even find one site with typical ...
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2answers
64 views

Are Add-On 10gb Nics Legit? [closed]

Sorry if this is product specific but I'm not sure where else to ask Are these AddOn nics legitimate 10gbE, or does anyone have any experience with them. There about 1/100th of the price of the ...
0
votes
1answer
23 views

Can I connect many on-prem sites to the same virtual network in Azure?

Here's a scenario: I have two branches in my company. One in Toronto, the other in Montreal. I have an Azure virtual network containing a variety of resources. I want to connect both of my branches ...
1
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1answer
72 views

What is the difference between an Up MEP and a Down MEP for Ethernet OAM CFM?

I'm having trouble understanding the functional difference between an Up MEP and a Down MEP in CFM applications. Some sites say they are defined based on network direction, others seem to think they ...