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Questions tagged [networking]

Managing and using network connectivity on a unix system

3
votes
1answer
2k views

How do I assign static IPs for HOST, BRIDGE, and GUEST

I am learning networking by building a small virtual network within a CentOS host. I need some guidance at the highest level to start planning: The Scenario: A CentOS 7 HOST needs to have a ...
2
votes
0answers
10 views

OpenWRT hairpin L2 traffic

I have an OpenWRT Router with embedded switch. I have a KVM machine with macvtap network access. I need guest to host communication. By connecting the host to my Cisco switch hairpin traffic is ...
8
votes
2answers
11k views

Why is dhclient making DHCP requests on a static interface?

I'm setting up a new Debian system. I have a static IP configured on an interface in /etc/networks/interfaces like so: # The loopback network interface auto lo iface lo inet loopback # The primary ...
23
votes
5answers
35k views

Why does SCP hang on copying files larger than 1405 bytes? [duplicate]

I'm trying to copy a file from one of my local machines to a remote machine. Copying a file with size upto 1405 bytes works fine. When I try to scp a larger file, the file gets copied but the scp ...
-2
votes
0answers
17 views

Can someone please help me connect to the Internet on Kali Linux? [on hold]

The two networks I have found are labeled 'lo' and 'eth0'. Neither have wireless extensions. I cannot access the Internet on Kali Linux right now. I am not sure what I have to do to do so. I have a ...
0
votes
1answer
1k views

Cannot ping VirtualBox VM using bridged network

I have a Fedora 22 laptop with a VirtualBox VM on it. All worked fine when I attached the VM to my wireless network card, but I want to attach it to my hardwired card because the wireless changes. But ...
40
votes
7answers
161k views

History of IP addresses that accesed a server via ssh

It has come to my attention that a server of mine has been hacked and infected with a known chinese botnet. It was a prototype/testing virtual machine with its own static IP(US address) so no harm ...
0
votes
0answers
342 views

Redsocks transparent proxy to SSH port forward: DNS not working

I am using redsocks to redirect local traffic for the postfix user to a system using SSH dynamic port forwarding. I am trying to use the redsocks dnsu2t module to do this. SSH doesn't support UDP with ...
2
votes
1answer
1k views

Setting multiple IP addresses on private network interface using Vagrant

I am trying to configure IPv4 and IPv6 address on Internal network Vagrant interface but I am unable to do so. Here is the configuration: config.vm.network "private_network", ip: "192.168....
17
votes
7answers
42k views

Is there a way to set network proxy system-wide?

If I want to have GNOME applications (as well as Firefox and Chrome) access the network through a proxy, I need only use gnome-network-properties (a nice and simple GUI I must say). For other apps (e....
0
votes
1answer
24 views

Netcat listens on a wrong port

When I run the command nc -l -p 443 it starts listening but when I try connecting to it it fails. A few hours later I tried with verbose mode nc -lvp 443 and it printed out listening on [any] 2443. ...
1
vote
1answer
3k views

Wi-Fi troubles on Ubuntu 16.04, using Qualcomm Atheros in a Lenovo v510

I have a Lenovo v510, running Ubuntu 16.04, and I can't get wireless networking to work.  'Enable Wi-fi' has no effect, no networks show up.  Some commands that I've tried, and their corresponding ...
0
votes
1answer
22 views

Seeing dead process in nethogs?

nethogs is a very useful tool to see which process(es) send/receive lots of network traffic. But as soon as the process exits, on the next display refresh nethogs no longer displays the process. Is ...
4
votes
4answers
2k views

Is there any way to see how much data I sent via Internet?

A big German ISP (Telekom) recently decided to volume limit their DSL internet connection to 75GB per month. Now I would like to know how much I download / upload. I use Linux Mint 14 Nadia and I ...
0
votes
0answers
36 views

How can I Improve the Performance of My Linux Netfilter module? [closed]

I wrote a very simple netfiter module. In it, I defined 3 hooks: localout and forward to change packets that go out of my PC and prerouting to do the inverse process. localout & forward hooks: ...
0
votes
0answers
18 views

Creating Iptables rules for router in front of several servers

I'm trying to create a test environment for some software I've written and I'm running into issues with creating the right iptable rules. I have a router that the rules are being written too, and I ...
1
vote
2answers
2k views

Debian Stretch won't resolve hostname, but IP works

I have configured Stretch networking for eth0 (it picked ens3), after setting: GRUB_CMDLINE_LINUX="net.ifnames=0 biosdevname=0" grub-mkconfig -o /boot/grub/grub.cfg reboot so now I have: >: cat /...
0
votes
1answer
643 views

Set SO_TCP_NODELAY (disabling the Nagle Algorithm)

As I know we have a socket option SO_TCP_NODELAY to disable Nagle Algorithm, and I found it is implemented in TCP/IP stack at https://elixir.bootlin.com/linux/v4.4.90/source/net/ipv4/tcp.c#L2401 . ...
10
votes
2answers
4k views

What's the “right way” to effect changes in /etc/resolv.conf with /etc/resolv.conf.d in place?

I the old days, resolv.conf was static and you edited it yourself. Later on, the DHCP client would rewrite it, using some static entries and what it got from the DHCP lease. These days, some ...
0
votes
0answers
26 views

My laptop doesn't detect my wi-fi

Recently my old dell laptop started to work very slowly, so I decided to install linux on it. I choosed debian (cause i like it). everything was ok, i installed drivers, programs etc. but when I tried ...
-1
votes
1answer
39 views

Packet loss on linux but NOT in a vm running on the same machine!

Something seems to be very wrong with my network stack right now. Not sure where to start debugging. I have Ubuntu 18.10 running a windows 10 VM with QEMU/KVM. The network is bridged together so both ...
0
votes
1answer
3k views

Centos 7: No Wifi Adapter found

I have dual booted centos 7 with Windows 10. Once centos 7 setup finished, no wifi connection was available. In the "settings > Wifi", I see a message saying "No wifi adapter found". My wifi adapter ...
1
vote
0answers
41 views

3 IP on one ethernet that not exist!

when i run "ip -d addr" show 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 promiscuity 0 inet 127.0.0.1/8 scope host ...
0
votes
0answers
18 views

Debian 10 wifi connection with heavy delay (but no package loss)

$ PING www.debian.org(klecker-misc.debian.org (2001:67c:2564:a119::148:14)) 56 data bytes 64 bytes from klecker-misc.debian.org (2001:67c:2564:a119::148:14): icmp_seq=1 ttl=56 time=19481 ms 64 bytes ...
3
votes
1answer
1k views

Sane can't see Samsung CLX-3305W network scanner in Ubuntu 14.04LTS

I've installed a new Samsung CLX-3305W multifunction printer/scanner a couple of weeks ago on a dual boot system with W7 on one physical drive and Ubuntu 14.04 64-bit on a separate drive. The printer ...
2
votes
1answer
7k views

Network UNCLAIMED - Unable to access internet

My Kubuntu was working well until I think a day ago, and suddenly I don't have access to Wi-Fi. I've tried turning on the connection via the Connection editor but the box was grayed out. After looking ...
0
votes
0answers
11 views

Could I deal with physical network layer via non-root application without writing networkcard driver? [on hold]

Could I get fast access to physical network layer using GAS or GCC made program running from shell? Are there possibilities to do it without own drivers creation?
0
votes
0answers
14 views

Can't connect to router

I have a problem with my fresh installed Fedora 30. I have internet access via LAN, but I can't ping my router or any website. Also no DNS server like Google's 8.8.8.8. If I look on my profile, my IP ...
-2
votes
0answers
15 views

Can't access internet connection for arch linux installation

My system: I Have 1024 megabytes of RAM, the processor is Intel Pentium(R) Dual-core CPU E5400 @2.70GHz 2.70GHz, manufacturer is biostar and the model is G31D-M7 and now I'm using windows 7 home ...
2
votes
2answers
8k views

Unable to connect to any wifi with NetworkManager due to error: Secrets were required, but not provided

Using NetworkManager on Arch Linux on a MacBookPro14,3, I am unable to connect to any wireless network. I've tried connecting to a number of different WiFi networks (home, mobile hotspot, work) all ...
1
vote
1answer
20 views

Default TCP KeepAlive settings

The TCP KeepAlive (socket option SO_KEEPALIVE) is governed by three options—time after which the mechanism triggers, probing interval, and number of failed probes after which the connecting is ...
1
vote
1answer
6 views

How to cleanup network interfaces after an LXC container crashes on startup

Today I modified an LXC container to add an extra "bind mount", but forgot to create the mount directory in the container root filesystem. As a result the container startup failed, and left the ...
1
vote
1answer
31 views

Is it possible to talk to a different subnet through another device?

I am trying to adjust the networking on a system so that two subnets can talk to each (ping) other via a device. Setup looks as follows: (192.168.1.128) (172.16.248.223) Router <------&...
3
votes
1answer
100 views

How to connect to ieee8021x Network using connman

Connect to my private WPA2 Wifi with connman works like a charm (followed this instructions). But when I try to connect to ieee8021x Network, i always get this error: Error /net/connman/service/...
0
votes
0answers
17 views

Swapping source and destination mac address cause packet to not be sent

I am currently testing a scenario using Python and scapy. When I send a packet which has a src mac of 80:CA:0E:BD:60:3B and destination mac of 82:DA:0E:BD:60:3A, the packet is sent out the specified ...
0
votes
1answer
1k views

Install brctl for OpenWrt - which package?

I'm getting an error in OpenWRT Attitude Adjustment that says: -ash: brctl: not found when I run brctl addif br-lan mesh0 I tried: opkg update opkg install brctl But I got this error: Unknown ...
0
votes
1answer
589 views

Unable to load SFP+

I am using CentOS7 7.5.1804. I have a Intel 82599 based 10gig SFP+ card. When I try my SFP's I get: failed to load because an unsupported SFP+ or QSFP module type was detected. I tried everything I ...
0
votes
2answers
880 views

KVM Linux guest cannot get network address

I use libvirt-manager to manager my VMs. I create a new VM, and a default virtual network, which uses NAT. virsh net-edit default gives me: <network> <name>default</name> <...
1
vote
2answers
47 views

netstat lists ip addresses not found in “ip address list” or ifconfig--what's going on?

My understanding was thatsudo netstat -tlupn gives me all the addresses/ports that have processes listening and that ip address list or ifconfig (though I guess the latter is deprecated) would give ...
0
votes
0answers
17 views

Alfa Awus036ach causes password prompt loop, won't connect

I want to use my Alfa Awus 036ach wireless card in my Debian 9 (stretch) system.  The system is dual boot; the other OS Kali Linux, where the cards works properly, so I assume this is not a hardware ...
72
votes
8answers
100k views

Simple way to create a tunnel from one local port to another?

I have a development server, which is only accessible from 127.0.0.1:8000, not 192.168.1.x:8000. As a quick hack, is there a way to set up something to listen on another port (say, 8001) so that from ...
0
votes
1answer
24 views

netcat no route to host on port 80 but not on 22

I am in a vpn into another country. I have a VM there that I can reach via ssh. It's awfully slow but it works. Netcat to port 22 also shows open port and reports with openSSH banner. So the routing ...
3
votes
1answer
41 views

OpenBSD Supported Hardware

I've recently installed OpenBSD on my Lenovo Ideapad 510s-14ISK. Unfortunately, it seems that my current network card (Qualcomm Atheros NFA435 QCA9377-5 / NFA 344 QCA6174 WiFi 802.11ac 1x1 + BT) is ...
1
vote
2answers
8k views

How to allow guest OS to access Internet in qemu?

I've created a Windows XP image and I'm booting it with qemu. When using "user mode networking" via -net user, my guest os (windows xp) gets the 10.0.2.15 IP assigned and I can ping 10.0.2.2 so ...
3
votes
3answers
416 views

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 ...
2
votes
0answers
142 views

Fedora 30 causes problem with MTU bug

The issue After installing Fedora 30 (KDE) on my laptop my router would crash shortly after I connected to it. This happened both when I connected through wired Ethernet and Wi-Fi. Fortunately, the ...
1
vote
0answers
32 views

Can I (IGMP) join a stream on two NICs and answer (IGMP) queries on both NICs in Linux?

I made a Linux application to receive multicast traffic. It works when I connect to one interface. When I connect to a stream, in Wireshark, I see an IGMP join, and when the switch sends IGMP queries, ...
3
votes
0answers
51 views

Why is my client getting two IP addresses when connecting to WiFi?

A sub-question: why is my client requesting a specific IP address without a dhclient running? I have two access points. One is serving up two SSIDs, the other just one SSID. When I connect to the two-...
0
votes
1answer
31 views

How Can I Make My KVM guest VM Accessible from the External Network?

I am creating a kvm setup for POC. KVM Host IP range: 172.21.158.0/24 KVM GUEST VM Range: 172.21.183.0/24 default virtual network with NAT forwarding :192.168.100.0/24 below are the guest vm NIC ...
8
votes
2answers
21k views

recvmsg returns 'EAGAIN (Resource temporarily unavailable)'

After a recent server move, we are troubleshooting this wierd issue of one of the server losing n/w connectivity for no apparent reason and regaining the connectivity in a few seconds or minutes. ...