Newest 'linux-networking' Questions

Q&A for system and network administrators

Host spontaneously looses network connectivity, but KVM guests stay online

This is a problem I've been somewhat ignoring for a few years now. I have a Debian stable server running linux 3.16.0-4-amd64. A few minutes to hours after booting, the server looses outbound network ...

Attach additional IPs to VPS (debian) and use these static IPs for docker

I created a VPS and added additional IPs as alias. So my /etc/network/interfaces looks like this: auto lo iface lo inet loopback auto eth0 iface eth0 inet static address 192.x.x.91 ...

Redirect all traffic from one ip to another

I have a server running Ubuntu with Strongswan installed, the server have a web server and an email server. The web server is allowed to be accessed from everywhere but the email server only allow ...

i install dns in centos machine but it not resolve ip to name and name to ip

i have some problem regarding DNS. i install DNS in centos 7 machine and my centos machine ip is 192.168.0.155 .if i run nslookup FQDN (centos7.unixmen.local) name then it resolve into ip means my ...

Understand interface TX & RX counters for bridged mode interfaces

I have a Linux gateway running interfaces in transparent bridged mode. Here eth0=WAN, eth1=LAN. Ideally, I believe eth0 RX = eth1 TX bytes and same way eth1 RX = eth0 TX bytes. But it seems huge gap ...

How to prevent process from knowing Network is up? [closed]

Fist let's block all Incoming, Outgoing signals via iptables. vi /etc/sysconfig/iptables *filter :INPUT ACCEPT [0:0] :FORWARD ACCEPT [0:0] :OUTPUT ACCEPT [0:0] -A OUTPUT -j DROP -A INPUT -j DROP -...

Can't access LXC container network Proxmox 4.4

I am setting up an LXC container on a fresh install of Proxmox 4.4. My network setup is analagous to the one described in this post: network configuration (bridging) proxmox However, I still cannot ...

Vnstat shows 500MB daily of RX transfer on non operational server

I'm running Centos7 on a VPS with apache and a 1KB php application deployed that i use for tests, the logs don't have any entries other than my own and a couple of bots. I have vnstat for tracking ...

Why does ping need to be restarted after connection is restored [migrated]

My laptop is running Fedora 25 (kernel 4.9.5) over a wireless connection. Sometimes my xDSL line drops and gets reestablished. I usually leave ping running and it shows this: 64 bytes from 8.8.8.8: ...

route loop while ping one server with 3 NIC in 3 separate networks

I have this server used for testing some network parameters. It has 3 separate network cards, each with the below IP configuration: 192.168.10.150/30 gw 10.149 192.168.152.146/30 gw 152.145 192.168....

Policy routing of packets arriving at specific virtual interface in LInux

I have one server with several IP addresses on one physical network interface (eth0:0 etc.). I want packets arriving at a specific virtual interface to be routed to specific IP addresses. I tried to ...

SFTP is periodically extremely slow for no reason

I am transferring a bunch of gigabyte-sized files using SFTP over a fairly fast connection, between two servers running Ubuntu linux, with not much CPU load. I am usually able to reach 5.0 MB ...

Do I need a physical switch to configure vlans in esxi [migrated]

My home network is very simple with a cable modem and a physical wireless router with four ethernet interfaces. I have a server with esxi, installed connected to one of the interfaces. I do not have a ...

Set the gateway by user

Is it possable to set the default gateway by user on linux? So for example the user bob would exit out 192.168.0.1 to get to the internet and then the user alice might exit out 192.168.0.2

How to configure multiple nics / ips on Ubuntu 14.04

I have a virtual machine running Ubuntu 14.04 running on some VMWare visualization framework. The machine is configured with multiple nics which are connected to two groups of IP addresses (each group ...

Debian - LSB: Raise network interfaces …29s / no limit)

My server has gone down after a restart and will not come back up. My provider scaleway has told me to use their ubuntu rescuemode script to get back into the server and mount the directories that my ...

how to find the timestamp that an interface flapped

could you please advise on how I could see when was the last time that an interface has flapped on a linux host ? (centos, if it makes a difference) i have tried the following: ethtool -S eth0 ip -s ...

Can't access jboss remotely despite of proper binding of IP address in standalone.xml file

I am using JBOSS EAP 7. I start it using the command sh standalone.sh -b 0.0.0.0 Following is my IP config when not binding explicitly from command line. <interfaces> <interface ...

Round robin & load balance to local port range using iptables on RedHat Linux

I wanted to implement load balancer (round robin) using 4 instances of ssh reverse tunnels running localhost:11669, localhost:11670, localhost:11671 & localhost:11672 connecting to remote host ...

How to make a linux VM working as a router

I have access to an openstack account where I can create Linux 14.04 VMs. I have created two network interfaces. 1."public-net" which is connected to the internet through a router 2."private-net" ...

Apply OpenVPN gateway to a single interface

I'd like to be able to use my VPN internet connection through tun0 for specific tasks as needed through commands like: curl --interface tun0 ipinfo.io/json My VPN provider pushes a new default route ...

Setting a 2-node local network with Internet access [migrated]

I want to set up a 2-node network. Both nodes are connected to a patch box and get their Internet access from there. Through their second NIC, the two nodes are also directly connected to each other ...

Routing based on destination port

Is there a way (probably with iptables) to route traffic to a specific router based on destination port. We have two ISPs. One which is very fast and reliable, but blocks some services. The other ...

Have Squid use IPv6 /48 block connected via tunnel

I have an Ubuntu 14.05 server running Squid. It has an IPv6 connection via Hurricane Electric's service. I'm trying to have every IP available to the server from the /48 they offer. I've searched ...

Different gateways for different IPs on same interface on Linux

I have the following question: considering the attached image: I have a server (RHEL 7) with 3 IP addresses (on the same physical interface): 192.168.10.1 (eth0, server address on network 192.168....

Why am I seeing IPv6 resolve errors despite having disabled IPv6 in bind?

I see lines such as Feb 13 21:45:48 srv named[2355]: address not available resolving 'secure.gravatar.com/A/IN': 2a04:fa87:ffff::c6b5:7405#53 Feb 13 21:42:29 srv named[2355]: address not available ...

Samba4: Possible to build a AD Forest

currently I have to set up a completly new AD infrastructure. Right now most parts in that company are run by NT-DCs untill now. I bought a new Server installing a Samba 4 (Version 4.3) domain ...

Fetch the particular columns in Postfix /var/log/maillog

I'm using Postfix in my local.I'm writing a script to fetch the deferred/bounced mail report for daily basis.If I'm correct,usually logs are printed like columns in log file. My proposal is I want to ...

Inject Delay between Virtual Machines in a VLAN

We'd like to simulate the impact of locality using VMs within a on a public cloud (say AWS EC2). To do this, we would like to inject delays in packets such that we can simulate a particular network ...

Ping to IPv4 works but IPv6 does not

I have a hosted VPS running on arch linux. I'm trying to make outgoing connections from this server, but all of them fail. After a little bit of debugging, I figured that the reason for failed ...

Application receiving boradcast from different subnet

I've 2 Linux boxes with following description Box A: Kernel: Linux 2.6 IP: 172.19.1.99/24 Box B: Kernel: Linux 3.14 IP: 192.168.200.100/24 Connected with Layer 2 switch Both boxes run a UDP ...

Determine process (and user) that is creating packets to given IP

Given an external IP address and target port, in Linux, is there any way to use something like ngrep or tcpdump to identify the process and/or user that is sometimes sending traffic to it? Or iptables ...

Strongswan - Split-tunneling

I have a server that is running Ubuntu 14.04.5 LTS on EC2 with strongSwan U5.1.2/K3.13.0-107-generic installed on it, currently i can connect through VPN and my traffic is routed to eth0 "the default ...

Linux set min_rto on IPv6 device

I came across http://unix.stackexchange.com/questions/210367/changing-the-tcp-rto-value-in-linux which pretty much does exactly what I want, but I need to do it with an IPv6 tunnel. $ sudo ip -6 ...

Samba 4: domain joined, but all users are mapped to nobody, and shares are inaccessible from Windows clients

I've got a Debian/Jessie Samba 4.2.14 running as an AD member. ADC is a Windows2008R2 server. Join worked without problem. # net ads testjoin Join is OK wbinfo -u and wbinfo -g work perfectly and ...

Debian Jessie - A start job is running for LSB: Raise network interfaces

This keeps happening anytime I reboot the server from my providers CP panel, has anyone got any idea what the solution to it is, it seems to be a known debian issue and has appeared on stack overflow ...

Why does Linux answer to ARP on incorrect interfaces?

I have the following Linux networking setup: there is an eth10 network interface with the assigned address 10.11.0.1/24. Then there is a tap0 network interface with assigned dummy address 0.0.0.1/32 (...

Networking Issue with Linux under Azure Site Recovery

I am trying to protect some on-prem CentOS 7.2 VMs running in Hyper-V using Azure Site Recovery. I have the replications to Azure running successfully, but when doing a test failover I cannot get ...

arp table doesn't show entry for macvlan interface after recent ping

Using Dedicated server. Main IP on eth0: 88.99.102.103 Default route: 88.99.102.65 Additional IP: 88.99.102.116 has MAC: 00:50:56:00:C4:6E Creating macvlan interface: ip link add link eth0 mac0 ...

Unable to remotely connect to Postgresql 9.5 instance

I am struggling to connect to a remote Postgres 9.5 instance running on Ubuntu 16.10. The usual: psql: could not connect to server: Connection timed out Is the server running on host "xx.xx....

Create a subnet using IPSec VPN?

Our devs are working on application where we need to frequently distribute small amounts of data to multiple locations which may change dynamically (servers may join and leave rather often). Some ...

Mosquitto MQTT - Not able to connect from external client

Ok, this has been throwing me for a loop for the past few days. Information I have Mosquitto MQTT 1.4.10 with WebSockets enabled setup and running on Ubuntu Server 14.4. Any client on my LAN can ...

How do I “share/route/tunnel” an ip addres from physical host A to B?

I don't know exactly how a SDN implementation would help my situation, but maybe somebody can clarify: I have physical hosts A and B. Host A has 5 ipv4 addresses routed to it and host B has one. I ...

programmatic access to “ip route show”

Is there a way to access information available in ip route show command via some special file (or other method), the same way that output of route -n can be read from /proc/net/route? I know that ...

Network eth0 no longer working on Ubuntu - no IP assign - time out on dhcpcd -T eth0

On Ubuntu 14.04 suddenly wired network stopped working. No IP adres get assigned. Syslog is below. There is a utility dhcpcd which shows a timeout. Not sure if it means anything. [user:~] 1 $ sudo ...

Bind9 timeout from LAN, server listening on port 53

I have a very wierd situation with Bind9 on Ubuntu Xenial. The server is listening on port 53 (tested with portqry from windows boxen that are trying to use it as a local DNS server) but it's timing ...

cannot obtain certificate from let's encrypt

I have a problem with obtaining a certificate from let's encrypt. My website is: www.webuilder.co.uk. All the time I am receiving an error like this: Error My settings are like this: Ubuntu ...

Can someone explain why I see different kind of slowness symptoms each time? [on hold]

Whenever I try to connect to office network from office, there is a network slowness due to VPN or my home network. I have seen two kinds of symptoms so far. I want to understand why I see different ...

Mellanox MT27500 Link to Port 1 is Down

I have Mellanox MT27500 dual port card which is installed on HP SL250s. Ubuntu 14.04.5 with 3.13.0-24-generic kernel is running on the server. Both port1 type and port 2 type are defined as eth. I ...

Can services on a 100.4.0.0 subnet connect to services on a 100.5.0.0 subnet? [duplicate]

I'm trying to figure out how to handle networking for a docker swarm. Specific usecase I may have upwards of a 1000 microservices I need for each microservice i.e. a group consisting of a db, app ...
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