Questions tagged [linux-networking]

Linux Networking refers to any networking function performed by a server running Linux. A Linux server operating as a router or firewall are the most common applications.

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Network issue in Linux Client

In the attachment I described my issue visually, can anyone suggest me that where could be the issue. The Green Color means, successful communication, and Read color means failed communication. For ...
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Track Bandwidth on shared interface

On our servers running FreeBSD, we've allocated multiple public ip addresses to host different clients on single eth0 interface. The purpose of allocating separate ip to each client is to distinguish ...
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SSH reverse proxying from multiple servers

I was able to reverse proxy from my macOS which worked fine but I didn't really understand it, I mean, I did but I can clearly see there are some gaps in my understanding, may be the concept of ...
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Failure to recv simple multicst packet traffic

I have a multicast src sending logging packets via multicast (226.1.2.3 port 9992) over ethernet (ifc em1) in a linuxlite box. Wireshark shows the (226.1.2.3 pt9992 ) packets arriving on the ethernet ...
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Linux server becomes unresponsive when local user logs out [closed]

So, my dad insists on hosting his own website from his own home computer. I set this up on a Linux Mint box, using a very simple server written in Go and this worked fine for years. Recently the setup ...
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Host SSH tunnel access from within rootless container run by Podman

Background System is running a rootless container based upon the docker.io/rocker/shiny-verse:latest image that publishes a port (say 8000) for remote web connections (to access the shiny ui). The ...
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1answer
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Using `ip address show type` to display physical network interface

Using Ubuntu 20.04. I have learnt in How to get only the name of the physical ethernet interface? that to display only the physical network interfaces, we could do ls -l /sys/class/net/ | grep -v ...
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How to investigate why my download speed from my dedicated server is capped at around 550KB/s? [closed]

I have an arm7hf dedicated server with 250Mb/s bandwidth. It has only 2GB of RAM. When downloading files from it my speed is capped at around 550KB/s. I have a connection of 40Mb/s. My torrent are ...
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CPU C-states disabling ruins network performance

With intel_idle.max_cstate=1: root@debian:~# curl -o /dev/null http://xx.xx.38.35:999/speedtest/1000mb % Total % Received % Xferd Average Speed Time Time Time Current ...
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1answer
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Uploading Sensitive Content to VPS [closed]

Despite hacking risks as Brute Force, DOS, Scam attacks, is uploading sensitive content to a VPS server safe, in a manner of employees reach those files and misuse them? For example, uploading credit ...
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How could I connect a public port to a different internal port?

I'm setting up a 2nd Plex server and I've decided to use port 32401 instead of port 32400 since I already have a Plex server running on that port. My issue is that Plex wants [publicip]:32401 to ...
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1answer
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could not resolve hostname with ~/.ssh/config and aliases

I have a config file ~/.ssh/config that looks something like this: Host *.texas User john Host *.texas !gateway.texas HostName %h.unitedstates.com ProxyJump gateway.texas Host gateway.texas ...
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How to Access Google Cloud VM from other Google Cloud VM in different region

Is there any way to Access Google Cloud VM from other Google Cloud VM in different region? I have seen that one of my US-Iowa 10.121.0.4 while Asia-Japan Region is 10.148.0.5 I was planning to host ...
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1answer
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iptables: employ DROP or REJECT rules in non-'filters' tables, namely the NAT table?

For an iptables(8) firewall that is otherwise "properly locked down" in the filter table, is there any use to employ DROP, REJECT or similar, terminating, "blocking or disabling" rules in non-filters ...
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1answer
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GCE: Instance has no connectivity after being cloned from a working instance

I'm currently trying to "clone" a working Ubuntu 18 instance. Essentially I just want to make multiple instances from a single preconfigured Ubuntu 18.04 instance. The preconfigured Ubuntu instance is ...
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How do I disable systemd-networkd.service so that connman.service can enable DNS?

I have Automotive Grade Linux (Halibut 8.0.0) installed on a Qualcomm board. This is an embedded system with no package manager, no build tools and no working DNS, but I can bring up ethernet okay. ...
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Ubuntu Server - Network card could not be found in ifconfig [closed]

I have problem with Ubuntu Server 18.04.4 on Virtual Box. I have one Network adapter enabled: Bridged Adapter. When I type ifconfig in Ubuntu Server only this is showing and I need IP address for ...
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Proxy service only responding on some IP addresses (others suck on SYN_RECV)

I have a server using a proxy service (WAF etc) which forwards packets to my server. I can see established SSL conenctions from all proxy netstat -an and the rest stuck in SYN_RECV: tcp 0 ...
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How we have differentiate the packet capture based on the RX & TX

I am working in the security industry. We have taken packet capture on the firewall multiple times. Can we take Pcap based on RX and & tx and force the tcpdump command to write the output in two ...
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ICMP BURST reported What option to check initial level

In case ICMP Burst reported and the source of ICMP request is the Server xx:xx:xx:xx where Application deployed. What Action to perform? /Suggestion. Disable ICMP Or Is their option to block this at ...
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incomming connection from GRE tunnel is always in SYN_RECV state

I create a GRE tunnel according to this tutorial : https://community.hetzner.com/tutorials/linux-setup-gre-tunnel/ in base server (server A in tutorial ) i have BGP advertise . when i enable the ...
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Debian KVM Server - Add Secondary Subnet

I have a Debian 10 server (from Hetzner) that I want to set up as a KVM host to set up virtual machines for myself. The server itself has a static IP like so: auto lo iface lo inet loopback iface lo ...
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1answer
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iptables-like NETMAP with nftables

using nftables, I need to NAT an entire subnet to another one for example: 10.10.10.1 -> 10.200.0.1 10.10.10.2 -> 10.200.0.2 ... 10.10.10.X -> 10.200.0.X nftables docs here shows multiple ...
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How to add IPV4 range to unmanaged server

I am really inexperienced with Linux and networking. I bought an unmanaged dedicated server running ubuntu 16.04. I am having problems with binding the ipv4/24 range with my dedicated server. How ...
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Would any port check command (telnet) work if sever application is not running? [closed]

This may be a simple yes and no question, but I haven't had luck finding answer anywhere. I am tasked with the installation of certain tools on server machines (RHEL based). The issue is, I need to ...
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Mapping suffix of DNS `A` queries in dnsmasq and pass mapped query to upstream

Let's consider that we have dnsmasq server (as forwarder) and it's get A query about resolving host-1.mycompany.com. Is it possible to forward from dnsmasq to upstream query about: host-1.yourcompany....
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1answer
35 views

How do I restrict access to all ports with source's PublicKey like SSH does?

I want a server to block any and all incoming traffic on all ports with the exception of the traffic from those machines which can be (and are right there and then regardless of the port being ...
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VLAN trunking on Linux Bridge

Local Lab Design This is the network diagram I am trying to implement. I have 3 VLANs whose description is given in the image and I am using Proxmox to create and configure virtual machines. When I ...
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cross-region load balancing: how to run two haproxies and serve geographically close clients

I may be phrasing this question incorrectly, so please feel free to suggest changes to the question if necessary. I run a web service. For both reliability and horizontal scaling, the front-end is ...
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Kernel networking offload— flow/flower/flowtable offload

I am learning network hardware acceleration in Linux kernel for quiet a long time, but there still are several problems that make me very very confused. I hope to get anyone's help. Thanks very much. ...
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1answer
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Can't get ARP reply on macvtap device

I have a physical server at Hetzner with two assigned public IPs in different /27 ranges. One is for the server itself and the other is for one VM inside it. The host is running CentOS 8 and libvirt. ...
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How do I add an extra bridge to a bonded interface using openvswitch

I need to add redundancy to my network, currently my public facing servers have one interface facing the internet and one going to my private network. This is all in the same vlan over separate ...
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1answer
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Redirect requests for specific domain to local ip adress of docker container

I have a docker container running flask on port 5000. I wanted that container to be publicly accessed, so I bound the port with:-p 5000:5000, and I run flask with: flask run --host=0.0.0.0. This does ...
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Monitor/view response codes of HTTPS traffic (e.g. port 443)? [duplicate]

Is it possible to monitor/view the response codes of traffic to a server with HTTPS? I can use ngrep or tcpdump to view HTTP (port 80) but this won't work for HTTPS (port 443) requests - they simply ...
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port channel delay coming up <> linux config

after our 5k switch reboots, due to many configured vlans, LACP/port channels take some time to come up. seems to be a serial process, and if vlans are at bottom of this list, it takes some time - ...
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1answer
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How to see if incoming HTTP requests are successful (view the responses) on Linux?

I'm really new to managing servers, and I've discovered that I can run ngrep and see connections from Google to our site (which is currently getting thousands upon thousands of 5xx errors and "crawl ...
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1answer
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Linux server dropping RX packets in __netif_receive_skb_core

I have an Ubuntu 18.04 server dropping received packets and I cannot figure out why. Here's a graph of dropped packets from netdata: The server is running multiple docker containers and networks, ...
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1answer
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Listing active machines in network?

I recently needed to patch almost 100 linux virtual machines on a subnet. To get a list of machines on the network I used nmap to retrieve all IP addresses in this network. The issue is that some of ...
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2answers
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iperf3 - discrepancy between TCP and UDP results

Recently I've done some network testing with iperf3 (3.1.7 on Centos 7.5 kernel 3.10, then I tried 3.7+ compiled from the source) and I'm confused about the results. The syntax I'm using is iperf3 -c ...
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NAT with strongswan - howto?

Network Topology I have the following setup where Office 1 and Office 2 have the same IP address range (192.168.0.0/16) and both are using strongSwan running on Ubuntu VM (with two NICs one connected ...
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glusterfs volume offline after reboot in centos

what is difference b/w glusterd and glusterfsd. Which one should be started at boot time? And what is the proper way of starting them after reboot? The gluster volume seem to be offline after reboot. ...
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2answers
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Connect servers in Internet via OpenVPN

I'm trying to connect multiple servers (Ubuntu Server 20.04) on the internet so they are in same private network and can share services that are only accessible through this private network (like ...
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2answers
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Multiple interfaces on one NIC

I managed to install Debian on my Banana Pi R2. This device has two physical NICs: one for WAN (1 port), one for LAN (4 ports). eth0 eth1 if I run ip address, I can see, that there are multiple ...
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Pingable device not detected by Nmap

I've used Nmap for quite a while and work with it on a regular basis as a network admin. Today I noticed something rather odd while scripting Android Development Bridge Functions, I'm able to ping and ...
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can't mount an SMB network share from Terrastation NAS on Raspbian LITE

i have 4 networ shares from the same NAS 192.168.178.165 folder 1,2,3 and 4. i created an share via mkdir /mnt/mydrive/1 and the same for the other 3 than sudo mount -t cifs -o username=XXX,...
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1answer
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In /etc/hosts file why would IPv4 hosts be different from IPv6 hosts?

Background: CentOS 8, Digital Ocean droplet. Question 1) I just looked at my hosts file in /etc/hosts and I noticed that hostnames listed under IPv4 and IPv6 are different. IPv4 lists example, ...
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Is it possible to keep interfaces down during boot in an LXD container?

I'm building a small tutorial-lab based on LXD (Ubuntu 18.04). I've created a virtual topology by creating several veth links and attaching the ends to the corresponding containers. When I start the ...
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Making an `ip rule` higher priority than `local`

I'm trying to redirect a subsection of incoming traffic to a different destination using fwmarks. The procedure 1) Mark matching incoming packets: iptables -t mangle -A PREROUTING -i pppoe0 -p tcp -...
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1answer
30 views

Route between two networks via multiple central routers

I have two networks, and a handful of computers. I want to fix the central point of failure. Two Networks: Network Foo: 172.16.1.0/24 Network Bar: 172.16.2.0/24 Five Servers, running linux (ubuntu):...
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2answers
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Inbound traffic is not working via public IP of server

I have two servers in a private network in our VPC, both have public IPs and private(10.0.0.0/24) subnet. Server 1 is configured to be NAT (ubuntu 18.04) Server 1 has only following configuration and ...

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