Questions tagged [networking]

Managing and using network connectivity on a unix system

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NetworkManager Default Connection Settings

I'm trying to modify NetworkManager's default DNS settings so that whenever I add a new connection it uses 127.0.0.1 instead of the default DNS for that connection. I still would like to be able to ...
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9 votes
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What network connections are not seen by netstat/lsof/ss?

Network monitoring tools ss, lsof -i, netstat -ltupw and similar have limitations like namespace and thus they don't show the whole machine connections. (for namespace created with ip we can see other ...
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Persistent network namespace configuration

When creating a namespace with ip netns add <namespace> the namespace and its related config are deleted on reboot along with created interfaces like veth pairs. What is the correct way to: ...
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8 votes
1 answer
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In Archlinux, it has a valid IP address, but no connection could be established

Later I changed a wireless router, and everything became OK. Maybe there was something incompatible between the former router and the latter. Yet I can't get the reason. --------update-----------------...
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7 votes
1 answer
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check the current backlog queue size

The sysctl netdev_max_backlog sets a limit to the maximum number of packets allowed in the kernel's backlog queue. Is there a way to check the current queue size (i.e., how many packets are currently ...
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7 votes
4 answers
10k views

Elementary OS shows WiFi networks, but won't connect

In the top bar, clicking the network icon shows a list of networks. My school's network, which on Windows I would connect to, and then visit a login page in Chrome in order for it to work, shows on ...
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7 votes
1 answer
8k views

Accounting for /proc/net/dev reported traffic

I noticed that according to /proc/net/dev I am constantly receiving around 6Kb/s on my wireless usb interface. But I can't account for anything even close to that with the individual connections that ...
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Docker containers have no internet access

So I am recently switched to Manjaro as my daily driver on my tower and my laptop. On both I experience the same issue: Docker container can't connect to the internet. I am testing this with docker ...
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6 votes
1 answer
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Arch Linux installation - no internet connection and can't ping gateway

I'm doing a clean install of 32-bit Arch Linux from a CD on a very old Panasonic CF-29 Toughbook. Trying to connect to the Internet from the terminal on the installation ISO is not working. I'm using ...
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6 votes
2 answers
4k views

AppArmor Profile: Deny internet access

I want to deny the internet permission for some applications. Therefore, I tried first to deny the internet permission for ping, but it doesn't work. Here is the profile of /etc/apparmor.d/bin.ping /...
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6 votes
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Using a bridge, an LXC container can't ping router, but the host OS can

I've got a virtual machine running under virtualbox, and in that virtual machine I've got an LXC container I'm trying to bridge to virtualbox's NAT interface: ------------- ----------- -----...
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5 votes
1 answer
129 views

What's the point of naming Iptables' tables as "tables"?

After reading some guides (e.g. this one) and playing with Iptables tuning I found that I see no reason for naming Iptables' tables as tables. I mean that there practically are no tables. E.g. having &...
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Docker mapped port doesn't show up on "netstat", "ss" and "lsof"

I've a question about docker containers and sockets. Today i've discovered that, docker containers with mapped port -p 80:80 (or etc ports) on the host system, doesn't show up when i use netstat, ss ...
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5 votes
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4k views

Enabling DHCP for IPv6 in netplan with networkd doesn't seem to do anything

I'm currently configuring the network interfaces for a Ubuntu 18.04 server, using netplan with the networkd backend. My hosting provider provides me with an IPv4 and an IPv6 for this server, however ...
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5 votes
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Why is systemd-resolved falling back to using Google Public DNS over IPv6 when I did not configure it to do that?

I'm having problems with SystemD's resolved service on Ubuntu 18.10 - on my wireless network we have an IPv6 subnet that is tunneled through some weird network setup (work stuff) and can't be used for ...
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Ubuntu pinging from link-local address instead of global

I have a network like this, (client 2001:10:1:100:0/64) -> router -> (server 2001:172:16:200:0/64) However, when I ping from client to the 172.16.200.0 network, (or anywhere) it always uses the link ...
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2 answers
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Backup and restore of Centos network interfaces

I have a server running Centos 7 which needs to be rebooted to upgrade some software. Some of the physical NICs have around 5-10 VLAN interfaces each. They're subject to change on a weekly/monthly ...
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5 votes
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RTNETLINK answers: File exists on Ubuntu Server 16.04

I have a fresh new install of Ubuntu Server 16.04. After installation, network connectivity was fine. I installed QuickBox, it's a seeding/torrent server software (https://quickbox.io). After the ...
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5 votes
0 answers
876 views

CPU high load native_queued_spin_lock

I'm using Debian 9(stretch edition) kernel 4.9., hp dl385 g7 server with 32 cpu cores. NIC queues are tied to processor cores. Server is shaping traffic (iproute2 and htb discipline + skbinfo + ipset +...
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5 votes
0 answers
1k views

Vagrant configure eth0

I started using Vagrant recently to quickly install virtual machines. I noticed that my network configuration isn't perfect, but I can't get it right. This is my Vagrantfile: ENV['...
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1 answer
766 views

Is there a way to simulate a socket stuck in CLOSE_WAIT or FIN_WAIT2?

I have a problem that I am trying to hack around where I have lots of local port forwards getting sockets stuck in CLOSE_WAIT and lots of remote port forwards getting sockets stuck in FIN_WAIT2. ...
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5 votes
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Simultaneous wlan0 & wlan1 access points (via hostapd)

I am trying to set up 2 wireless access points from linux device (Debian Jessy). Both AP's should work simultaneously & share Internet connection (as shown below). _____ ___________ ...
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5 votes
0 answers
1k views

Linux netconsole with bridged interface

I'm attempting to enable netconsole on my home PC, however encountering some trouble with my bridged LAN and Wi-Fi. If I don't specify an interface name, it fails as follows: $ sudo modprobe ...
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5 votes
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Resolve NetBIOS Names via Samba >= 4.4

Through StackExchange, we know how to configure Linux to resolve NetBIOS names with older versions of Samba, and I have configured my system in those ways. (I have installed winbind, configured my /...
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Allowing GRUB to access network in BIOS mode

I want grub to fetch some configuration via tftp/http. Using efi I can do insmod efinet and net_ls_cards will list my network cards which I can configure and use. Using PXE in BIOS/legacy mode ...
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How do I disable network interfaces from loading at boot without Network Manager?

The machine I'm using has 4 network interfaces, only one of which is currently being used (the other 3 are not plugged in at all). Currently when the machine is restarted it is delayed by a few ...
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5 votes
1 answer
557 views

Is it possible to set interface name permanently in Raspbian?

I'm using 2 wifi dongles. First one is used to monitor and second one is used to access internet. Even if I changed /etc/udev/rules.d/70-persistent-net.rules as below, at startup sometimes wlan0 ...
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5 votes
2 answers
1k views

Tons of unknown connections in nethogs

I am seeing hundreds of different connections to the same ip and port scrolling by when running nethogs. Occasionally the foreign IP and port will change (not always 80, but sometimes). I've noticed ...
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2 answers
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Problem when trying to cross-compile an ethernet driver on an old Linux kernel

I'm currently trying to cross-compile a network driver against an old Linux kernel, in version 2.6.27.7 but the compilation fails and prints: make[1]: entering directory « /home/johann/Desktop/linux-...
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5 votes
1 answer
1k views

Where did pand go?

Most guides on setting up a Bluetooth access point use a program named "pand" to do so. Seemingly, this program was dropped in bluez5. How can PAN be set up without it?
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5 votes
2 answers
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Issues with connecting to open WiFi network via /etc/network/interfaces

I've previously been able to connect to an open WiFi network on a BeagleBone with a WiFi dongle by adding the following to /etc/network/interfaces: auto wlan0 allow-hotplug wlan0 # For automatic ...
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4 votes
1 answer
206 views

Does Linux keep a per-host MTU table?

I'm experimenting with an IPv6 route that involves a 6rd (6-over-4) router, and I notice that when I use a packet size that is small enough to fit in the segments of the route that run native IPv6 ...
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4 votes
0 answers
36 views

How can i find out which network interface managing solution is used on a given linux distribution in an easy and robust way?

I frequently find myself sitting in front of various different Linux installations and need to check or change network settings. They are different versions from different distributions (mostly debian ...
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4 votes
1 answer
1k views

WiFi suddenly stopped working on Ubuntu 18

My Situation is exactly equal to OP's from this question (except for the exact hardware configuration; I can add some more details if needed), but the answer that fixed the issue there didn't work for ...
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4 votes
0 answers
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Is there a command like `time` that monitors the network traffic of commands?

I can use the time command to measure the time some command takes: time node -e "" node -e "" 0.06s user 0.01s system 92% cpu 0.076 total Is there a similar way to measure a ...
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4 votes
0 answers
669 views

WiFi dropping only on Ubuntu

I am having a lot of problems with Wi-fi. The strange thing is that happens only on my Ubuntu 18.04.4 x86_64 (4.15.0-101-generic) computer, all others have Windows and are not affected. What happens ...
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4 votes
1 answer
358 views

Way to limit number of ports a single user can bind to concurrently

On Linux, is there a way to limit the maximum number of simultaneous ports a single user can bind/listen to (possible on a per network device basis) at the same time? I.e. if users can bind/listen to ...
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  • 180
4 votes
1 answer
439 views

veth interfaces performance problem

On a fast AWS machine (m5.2xlarge), I am creating around 600 veth interfaces, each one having a little server (with socat) running on a port. I then start sending around 7kb/second of data per server....
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4 votes
0 answers
193 views

Is there something like 'sudo' but give only one capability not real root?

I want to run a one-time web server on port 80, which I will never run again. Is there something like 'sudo' that gives only temporary CAP_NET_BIND_SERVICE, not real root, to a process? So that we ...
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4 votes
0 answers
1k views

I can ping across namespaces, but not connect with TCP

I'm trying to set up two network namespaces to communicate with eachother. I've set up two namespaces, ns0 and ns1 that each have a veth pair, where the non-namespaced side of the veth is linked to a ...
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4 votes
0 answers
378 views

Why does a wireguard VPN require forwarding for all networks?

I have a wireguard peer (server), and two clients (clientA & clientB). They have the IP addresses fd16:17:18::1, fd16:17:18::2, & fd16:17:18::3 respectively on the wg0 interface. When all of ...
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4 votes
0 answers
286 views

Does Linux network device have its own queue to hold incoming and outgoing packets?

I am trying to understand how Linux handles packets for ingress and egress through any device. Taking a simple example of a veth pair (say veth1 and veth2), when a packet is sent via veth1, it will ...
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4 votes
0 answers
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What happens when you disable NFS server delegation?

We are facing issues with NFS 4.1 on RHEL 7.6. We have a lot of applications on this server and GitLab is one of them and it is impacted the most. Excessive NFS network traffic (due to a bug with NFS ...
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4 votes
0 answers
920 views

how to prioritize udev-rules over the driver/kernel (network interfaces names)?

I have an ubuntu server 14.04 virtual machine with 2 network interfaces eth0 - for web management, SSH eth1 - for incoming span network analysis I've configured the machine with udev rules (to ...
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4 votes
2 answers
2k views

QEMU - network bridge

I'm setting up a VM on Debian 9 using QEMU (and KVM). I'm currently trying to make it work through a bridged network, which I have set up using ip link, ip tuntap etc; here is the output of brctl show:...
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4 votes
0 answers
489 views

htb -> netem -> pfifo_fast qdisc drops all packets under high traffic

I configured a OpenVSwitch-based topology using Mininet on my local machine: h1 (server) -------(eth1) s1 (eth2)--------------- h2 (client) (eth3) | ...
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  • 153
4 votes
0 answers
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Entries order in /etc/network/interfaces

I have a device with two interfaces, eth0 and eth1. One should get its IP from a DHCP server and the other should get its IP statically. If my /etc/network/interfaces file is configured as follows: ...
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4 votes
0 answers
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No buffer space available - ICMP

I'm trying to set up a Heartbeat client on a linux machine (CentOS Linux release 7.3.1611) which is sending ICMP echo requests to roughly 1300 hosts. However, in future this number will be higher. The ...
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4 votes
0 answers
2k views

"Read-only file system error" on Samba share, alternative share with identical options working (Linux client)

I'm experiencing a very strange problem which I've been trying to solve in the past few days and I already tried various methods of resolution to which I will get to in a moment. My home network ...
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4 votes
0 answers
13k views

I'm unable to create a static ip route. error says: RTNETLINK answers: Network is unreachable

Im trying to setup a test network with VMs to practice how static routing works, so what I thought to do is to setup two internal networks and one box with two interfaces to work as a router, here's ...
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