Questions tagged [networking]

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

3,235 questions with no upvoted or accepted answers
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11
votes
1answer
10k views

Adding second network interface to Ubuntu 18.04 on AWS EC2

The provided 18.04 AMI comes with one interface, and I am adding a second one with its own IP (for stuntman-server). However the instance is only responding to one elastic IP or the other, not both (...
9
votes
1answer
1k views

Troubleshooting Redmine (Bitnami Stack) performance

I've got a Redmine instance (Bitnami Stack) that's unusually slow. Because I'm just trying to get to the bottom of this, I have some theories which I'd like to discuss here. So, if anybody has any ...
8
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2answers
535 views

Cisco DNS doctoring or Hairpinning?

I've the following configuration: CISCO 881, IOS 15.2(4)M6. On WAN interface is configured the 86.34.156.48/29 subnet from our ISP. Behind the router is staying 2 webserver. NAT: 86.34.156.51 <> ...
8
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0answers
161 views

Configure Juniper M320 as Ethernet/STM transparent converter

There is Juniper M320. We need to move ALL the traffic from one port to another. Everything that comes to one port goes to another and vice versa. No snooping or any other processing is required. One ...
7
votes
1answer
149 views

Can network packet corruption affect only one server process out of many that are talking to the database?

Context We saw sporadic ActiveRecord::StatementInvalid errors from MySQL servers over the course of 4 hours yesterday. The errors haven't happened since then. Strangely, SQL statements seemed to ...
7
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1answer
10k views

SNMP differences in ifInOctets vs ifHCInOctets values

I'm trying to graph network usage on my router for a specific interface using data from SNMP. I know that ifInOctets/ifOutOctets is only 32 bit and will overflow for high speeds and make my graphs ...
7
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0answers
2k views

DHCP interface never transitions to configured state in systemd

I have a server running CoreOS, and my main network interface that gets configured via DHCP gains a carrier and is routable, but never leaves the configuring state. This causes systemd-networkd-wait-...
6
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0answers
1k views

Why multicast UDP can be slower than unicast UDP?

I have two machines (with Centos 7.3 on both) connected via 1G switch. When I measure UDP thoughput between macines with iperf it gives about 850 Mbit/s. However when I measure multicast UDP thoughput ...
6
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0answers
1k views

meaning of 'event_wait : Interrupted system call'

I manage several OpenVPN links. Sometimes while the VPN connection is UP for a few minutes/hours it suddenly gets down with the following (error) message: event_wait : Interrupted system call (code=...
6
votes
3answers
181 views

How to make a disconnected drive?

kind of a weird question but how do I make a drive go from a OK state to disconnected state using net use? I do not want to delete it. I am testing a script but the annoying thing is that to test the ...
5
votes
1answer
81 views

High Network I/O Between Docker Swarm Managers

Network Traffic We run Docker Swarm with 3 manager nodes and 16 worker nodes. The network I/O between two of the three manager nodes is very high. To illustrate this, here is the output from iftop ...
5
votes
1answer
119 views

OpenBSD not responding to arp queries

I am setting up an OpenBSD system as a router, I have one interface as the upstream, then another with a vlan configured: Upstream(em0): inet 10.0.2.20 255.255.255.0 NONE description upstream ...
5
votes
1answer
337 views

How long is an (accepted) ICMP redirect observed for, and how can I shorten that time?

If a Linux host receives and accepts an ICMP redirect (accept_redirects=1 on the interface in question), how long is this route being cached for and observed? Can I lower that time? I am asking ...
5
votes
1answer
334 views

How to debug failed checksums/flipped bits in TCP packets?

A web application we maintain recently encountered a very weird problem: three out of four virtual machines on two physical hosts had trouble connecting to the server of our payment provider via HTTPS....
5
votes
1answer
1k views

Access to service in Docker container connected to VPN

I set up a Linux server (VirtualBox VM for now) In that server I run a Docker container containing two things: An app with web interface on certain port Open VPN Client I can access that app (from ...
5
votes
0answers
1k views

Is RSS (receive side scaling) in Windows considered unstable?

When asking a customer to enable RSS in their data center to improve network performance (very high UDP packets-per-sec rate), I was told that they generally turn it off, because after various ...
5
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0answers
939 views

IPSec bandwidth between two Pfsense hosts has predictable, variable bandwidth

I have a IPSec tunnel between two Pfsense machines. Both machines are connected to a 100mbps symmetrical connection. The latency between the two routers is ~70ms. I'm using AES-GCM-128 and SHA1, both ...
5
votes
1answer
618 views

Open Source Puppet for Network Devices

I'm attempting to determine whether I'd be able to run Puppet on network devices (switches, firewalls etc.). From what I can tell after reading online documentation, Puppet Enterprise will cater such ...
5
votes
1answer
5k views

Unable to make work both private and public ip network on openvz container in Proxmox

I'm using Proxmox 3, it is a fresh installation. For those who know, I'm using OVH Vrack 1.5 (along with a previous Vrack 1.0). My server has two interface eth0 and eth1, I succeeded to configure ...
5
votes
0answers
15k views

ActiveMQ - “Cannot send, channel has already failed” every 2 seconds?

ActiveMQ 5.7.0 CentOS release 6.3 java version "1.6.0_26" Application server: Tomcat In the activemq.log, I'm seeing this exception every 2 seconds: 2013-11-05 13:00:52,374 | DEBUG | Transport ...
5
votes
0answers
4k views

NAT64 configuration with tayga on Debian 6

I'm trying to implement NAT64 with tayga on my server and came to a point where I'm not sure how to proceed. My server is connected via one IPv4 address and one /64 IPv6 address block to the internet....
5
votes
1answer
622 views

Getting 10mb/s speeds on a 1gb network

I'm at a loss and I've scoured the internet for answers, but none of them seem to work. I have a TP-LINK TL-SG108E 8 Port Gigabit Easy Smart Switch, a desktop, a laptop, and my new Synology 918+ that ...
5
votes
1answer
2k views

docker network freezing randomly

Sometimes , all network's of my dedicate server is freezing (ssh also not working). it's randomly repeated. OS: Ubuntu 14.04.3 LTS On server installed docker containers, and i see in dmesg logs: [...
5
votes
1answer
1k views

Enabling IPv6 with OpenVZ using Proxmox 2.2

I'm trying to enable IPv6 on my Debian nodes (OpenVZ) using venet; my host is under Proxmox 2.2 (kernel 2.6.32-16-pve), and it seems the routing fails. My host correctly pings all my nodes; all my ...
4
votes
0answers
299 views

Docker - Is it possible to create an IPv6-only bridge network?

Is it possible to create a custom bridge network that only has IPv6 address? When I try to create a custom bridge network in the following way: docker network create --driver bridge --ipv6 --subnet ...
4
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0answers
1k views

Getting to enforcing google safe search using CNAME with unbound and nsd?

I am trying to implement this using Unbound and Nsd: https://support.google.com/websearch/answer/186669?hl=en To force SafeSearch for your network, you’ll need to update your DNS. configuration. ...
4
votes
0answers
1k views

What is WebProxy/1.0 Pre-Alpha?

I have had 504 errors from my domain throughout the day. The back end servers look okay and the CDN provider (Fastly) doesn't think it could be them. Looking a little closer I see the following header ...
4
votes
0answers
5k views

How can I identify a rogue IPv6 DHCP server on my LAN?

This will be kind of a long post, but I want to give complete information. I have a home/business LAN with isc-dhcp-server running an ipv4 dhcp server and bind as a DNS server running on an ubuntu ...
4
votes
1answer
109 views

How to let chef listen on multiple IPs

I'm currently playing with chef to evaluate whether or not such a configuration tool might help us in our *nix-based environment. For the last few days I'm struggling with one problem I can't find a ...
4
votes
1answer
1k views

Make SSH server to forward connection per user

Is there any way to force OpenSSH (or create a proxy of some kind) to forward one user to one machine and another user to another machine just by the username that he (or she) provided? I've got ...
4
votes
1answer
3k views

Windows 10 arp cache getting stuck after failed attempts when target machines are offline

After upgrading our development team to Windows 10 from 7, we are experiencing an issue with the ARP cache where a machine has the correct IP-MAC mapping cached, but the type is invalid due to failed ...
4
votes
2answers
222 views

How can I provide services to an internal air-gapped extranet

Background - "Extranet" We have about a dozen users that are on what I would call an Extranet. It is an air-gapped LAN that is physically in the same location as our primary LAN. We share ...
4
votes
1answer
251 views

Windows port forwarding, local machine to server

I'm working on Windows 8. I'm trying to connect to an OpenStack cloud which is hosted on a remote server but has a public IP to the API. However, making API calls require calls to additional services ...
4
votes
0answers
485 views

VLAN Communication between Cisco ASA 5510, and VMWare ESXi 5.5

I've having a problem, where my Cisco ASA 5510-v8.2 can't communicate with VM's in a VLAN specific port group. The Cisco ASA is currently sitting in front of a group of VM's that have public IP's. ...
4
votes
0answers
166 views

Breakdown Windows Network IO by network adapter and by process

What I'm trying to do is breakdown the Network IO by network adapter and by Process. The goal is to identify which processes are generating the most IO on a certain network adapter. Resource Monitor ...
4
votes
0answers
539 views

pppd terminated bya SIGTERM in Centos 7 — who's sending it?

Folks, I created a script to keep a persistent "emergency" connection with a 3G modem, so I can access my CentOS 7 makeshift server remotely if the usual network fails. Everything works for a few ...
4
votes
0answers
6k 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 ...
4
votes
1answer
1k views

Server 2008 R2 NIC in “Unidentified Network” state after connectivity loss is restored

I am having trouble with 2 servers, both with the same symptoms. When they are reconnected to the switch after losing connectivity, they stay in an "unidentified network" state. Only after cycling the ...
4
votes
1answer
839 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 ...
4
votes
1answer
383 views

psping to localhost - improve throughput

I'm using following psping command to measure the bandwith throughput for localhost on a physical server psping -4 -b -l 8k -n 20000 localhost:1234 The throughput is around 150MB/s wich isn't all ...
4
votes
0answers
3k 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 ...
4
votes
0answers
2k views

Why is the first of two post-up commands for routing in interfaces configuration not automatically processed

We managed to connect our servers to two distinct networks and everything works fine. We use routing rules that ensure that server responds to the right network. I followed the instructions under ...
4
votes
1answer
523 views

VMXNET3 nic loses the ability to update ARP table after N hours

I have a fedora 18 VM that stops updating the arp table on eth1 after running for a number of hours to days. There are other VMs on the same hypervisor that can access all of the same networks without ...
4
votes
1answer
611 views

Automating Configuration of VMware's vSwitch (OpenStack/libvirt/Nova)

There's a lot of talk now about VMware integrating with OpenStack now. I've noticed that Nova network service is working with VMware's standard and vDS. Deploying a full OpenStack instance is not ...
4
votes
0answers
366 views

Configuring Container with bridges and vlans (server only?)

I have two groups of lxc contianers on a server and want to isolate their network traffic for security reasons. I will be using port forwarding so the containers much each have separate IP's. I know I ...
4
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0answers
3k views

Wireless router country codes: what issues can these actually cause?

Running the network diagnostics tool on my Mac, I get a messaging about "Conflicting Country Codes" stating that: "A nearby wireless router has been detected which is identifying itself as ...
4
votes
1answer
1k views

Change TCP wait for ACK timeouts in Win7/WinServer

Is there any possibility to change default wait for ACK timeout in TCP network on Windows 7 or Windows Server ? I'm using very slow network ( 1200 bps ) and want to tweak TCP. When using default ...
4
votes
0answers
694 views

snmp MIB-TCP::tcp not showing any usage

I am trying to configure MRTG on all of my servers for making a network weathermap, this requires running SNMP which MRTG gets the information from. So, I installed it on two servers the exact same ...
4
votes
0answers
2k views

Windows Filtering Platform blocking packets for legitimate traffic

I am running into an issue with traffic from a webapp server to a database server being blocked or filtered. I have allowed inbound and outbound traffic on the needed ip and port with a firewall rule, ...
4
votes
1answer
1k views

keepalived config is not working correctly with virtualbox vms

my keepalived configuration is not working correctly. I have two virtual testing machines (virtualbox) to try some things out with keepalived/vrrp. Bot can ping each other flawlessly (internal ...

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