Newest 'linux-networking' Questions

Q&A for system and network administrators

dhcpcd client not sending DHCP request after getting DHCP offer from two relay agents

I have a endpoint which is connected to vlan x, which has two DHCP relay agents(10.0.208.2,10.0.208.3) and my DHCP server is located at 139.23.64.170. One of my endpoint is connected to same vlan as ...

Getting Nagios on an Ubuntu server to talk to NSClient++ running on Windows server on a WAN

I have installed freeSSHD on my Windows machine, created a user, enabled tunneling, copied over a public rsa key, and installed NSClient++. On my Nagios server, I have Nagios running and a Windows.cfg ...

I can’t connect to my Azure VM

After I used this command: ifdown eth0 can't connect to my VM (centos 6 ) with ssh on cloud microsft azure. How can I fix it?

How to create a protocol-based default route using iproute2

I'm trying to create two routes -- Send all packets with IP protocol version 100 to 1.1.1.1 (via device eth1) Send all other IP packets to 2.2.2.2 (via device eth2) Reviewing the man pages of ip-...

Does bonding 3 1G NICs into one make a 3G NIC?

For example, I have 3 NICs (1GB) and make a bonded NIC. Do I get a 3GB NIC? Should I connect these 3 NICs into 1 switch? If one NIC dies, do I still have the network between server and switch alive? ...

How to ask dnsmasq to not allot few IPs

I am running DHCP server using dnsmasq. My DHCP server is configured to provide IP address from a subnet (say 192.168.49.0/24 with a gateway ip of 192.168.49.1) What i now want is that the DHCP ...

creating virtual bridge breaks host network

Tried to set up virtual bridge on a Ubuntu machine, and host network broke #ip link add name br0 type bridge #ip link set dev eth0 master br0 #ip link set dev br0 up #ping <gateway_addr> // ...

How to add a secondary ip address permanently on fedora linux 25? [duplicate]

Lots of examples out there to do this temporary, but can I make this secondary IP address permanent, so that it survives reboots "the fedora way", or does this really need some kind of non-standard ...

Sharing a scanner using SANE on newer Fedora Core versions

I'm trying to set up network scanning on a newer Fedora Core 24 machine and all the guides I've been able to find seem to be a bit outdated (Fedora Core 10/14). They talk about setting up a xinetd ...

Ifupdown fails to bring down hostapd

I have ifupdown set up to act as an access point under debian Jessie. When i bring up the interface, it seems to work just fine, my clients can connect, etc. When i do ifdown <interface>, ...

LXC CentOS Container does not work with multiple IP addresses

Hoping someone can help me as i've been pulling out the only hair I have left (which is not much) trying to figure this out. I'm unable to assign multiple IPs to any CentOS 7 container, only the ...

How does switch know which switch to send data?

For example SW1 / | \ server1 SW2 SW3 | | \ server2 server3 server4 If server3 send data to server4, SW3 ...

Forwarding outgoing traffic to different port

The application in my linux box is connecting to "ip.example.com". The ip address for "ip.example.com" is defined in /etc/hosts as 10.23.22.1 ip.example.com At the destination IP, a service is ...

Change netmask in openvpn

I have an openvpn with netmask /27 but I need more addrrsses for clients, the question is how can I do it? Can I change netmask on my openvpn server config to /26 or I have to rebuild openvpn server?

LACP bond work intermittently on Cisco N5000

Our clients are using Centos 7.1 and 7.3. They are two 10GB card bonded to make a 20GB link. Each of the network card is connected to a pair of Cisco N5000 switch. While running cp or iperf, I can see ...

What is the mean of ip route show

10.1.40.0/24 via 10.255.115.1 dev eth1 10.255.114.0/23 dev eth1 proto kernel scope link src 10.255.115.18 default via 10.1.1.1 dev eth0 metric 100 Am I understanding correctly? packet goes to 10....

HAProxy Interface/eth aware binding as non root user

I have 2 network interfaces on my instance (eth0 and eth1) I am trying to setup HAProxy to be interface aware and have separate frontends per interface. The config below works as root (ie. i do not ...

'vmxnet3' is not a valid device model name despite having VMTools installed on CentOS 7

I am trying to use the 'VMXNET3' driver for my ESXi guest on KVM. I installed the VMtools as required but still got the 'invalid model name' error. My host OS: # cat /etc/*release CentOS Linux ...

SSH Accessible Raspberry Pi shut off from the internet [closed]

Excuse me for this peculiar question, I tried googling it but obviously I don't know how to phrase this question correctly. I'd like to make a sort of home server out of an RPi (RPi == Raspberry Pi). ...

How to debug some connections not reaching my NGINX servers (connection timed out)

I have a few Ubuntu servers running NGINX as reverse proxy to my application services. In front of these Ubuntu/NGINX servers resides a fleet of other NGINX servers basically load balancing connection ...

FirewallD - Trusted Zones / Drop Zone and Tracerouting

Im using CentOS 7 and I have an issue where I am trying to lock down a server to only accept SSH from any private IP ranges of 10.0.0.0/8 which is in the work zone, and 10.0.20.0/24 for any connection ...

why is echo “ens6f1” > interpreting as ns6f1 ie with out “e”

i am trying to execute echo "ens6f1" > /sys/class/net/bond0/bonding/slaves but getting error: bond0: Interface ns6f1 does not exist! is this an "echo" issue or some issue with the file which i ...

Search domains in Debian 8 with systemd-resolved

I'm running Debian 8 + systemd215. I'm trying to setup domain suffix to be appended automatically, when I ping other hosts in LAN. Before systemd I'd just add below line to: #/etc/resolv.conf search ...

Why first hop of traceroute is not the default router?

default route is: ip route show: 10.0.0.0/23 dev eth1 proto kernel scope link src 10.0.0.150 default via 10.1.1.1 dev eth0 metric 100 And traceroute www.google.com traceroute to www.google....

Making static route persistent after reboot on linux

I have two interfaces with different networks on server. Since I want to have both of them available, I had to create static route for one of them. I did that by creating entry "1 local" in /etc/...

Two IPS on the same subnet pinging but not working as primary goes down

I have few Linux RHEL 6 Server where i have configured 2 separate NICS in the same subnet with 2 diffrent IP's. > example: > eth0 : 172.23.23.1 > eth1: 172.23.23.2 Initially i ...

what are the normal server isolation technologies?

We have some development servers which are used by outsourcing companies, from these development servers, they can ssh into production database servers, can you tell me how to isolate servers from ...

systemd: when during boot are network interface devices created

I'm trying to create a custom network management service for a CentOS 7 netboot image. The service gets a list of all interfaces on the host, finds one with a physical connection, and then uses it to ...

ARP request being sent to external IP addresses

I have an Ubuntu 16.04 machine. Here I create a virtual tunnel (tun) interface and make it the default route so that all traffic pass through it. I have a C application listening on this tun interface ...

DEFROUTE vs GATEWAY in RHEL7

I've disabled Network Manager and I'm using ifcfg- scripts for network configuration. And I'm trying to find the difference between DEFROUTE="yes" and GATEWAY options. I understand that "ifcfg ...

Linux ethernet bridge can be accessed behind a router

I run Debian 8 and need to bridge a tap interface tap0 to eth0 (trying to setup an OpenVPN server). I use the standard bridging script from OpenVPN help page: #!/bin/sh # Define Bridge Interface br="...

How do I pass VLAN traffic over a bridge to KVM VM's

I have a KVM host that I would like on VLAN 1 and I would like the VM's to use VLAN 2. emo1 on the host is bridged with br0 and the physical interface is connected to a trunk port on a Cisco switch. ...

mySQL Workbench on Windows through two SSH hosts

I'm attempting to connect to mySQL through two SSH hosts and haven't been able to find a solution anywhere online. If I were connecting with Putty, I would connect to the first box (let's call it ...

VMware customization specification for Linux CentOS server not prompting for gateway

So I created a customization specification in VMware 6.0.0 and configured it so that it prompts the user whan a vm is deployed from my CentOS 7 template. The ip address, subnet mask and hostname are ...

How to find out the interface inbound traffic is using?

For a outgoing packet, by route I can know which interface is using, but for a incoming packet, how to find out which interface is using?

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 ...

Virtual network interface for DMZ [closed]

here is the situation. I have a laptop with two physical network interfaces: eth0 and wlan0. As an exercise i am doing some experiments with iptables firewalling, at the moment i receive internet ...

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 ...

devstack and physical network configurations

I'm a newbie of OpenStack and I did not have many experiences on network configurations with physical servers. I'm going to prepare 2-node (1 controller embedding network node, 1 compute node on each ...

IP Alias/Virtual Interface for ESXi on KVM/libvirt

I need to run two ESXi hosts on KVM and assign them distinct, external IPs visible to the external network. Desired topology: ESXI ESXI ↓ ↓ KVM KVM ↓ ↓ vIF ...

Linux: slow SSL handshake due to delayed client hello

While investigating an issue afflicting a cluster of proxies which are all affected simultaneously, I've found weird behaviour in the establishment of SSL connections. The symptom is that outgoing ...

Is it possible to masquerade a packet on a bridge?

I have a container which has an incoming VPN. A connection into that container will be assigned the 192.168.10.10 IP. The virtual NIC of the container has an IP of 10.10.10.1 and a gateway (on the ...

Reassembly fails at destination

Say I have Host1 & 2 connected to a router with different speeds. Host1 <--100 Mbps--> Router <--10 Mbps--> Host2 Host1 sends 10MB of UDP data using nc command to Host2, but the ...

bond failing to start the backup network card on failure of main one

Our production server has 4 network cards, linked 2 by 2 on 2 bonds. External network: bond0 : eth0 up & running, eth1 active-backup Internal network: bond1 : eth2 up & running, eth3 active-...

RSS (Receive Side Scaling) [duplicate]

I need to know how much performance can be gained by enabling RSS (Receive Side Scaling). I only find results showing that data is being distributed among CPUs, but I can not find any number on how ...

add default route for redhat permanently

I have a cluster consists of several RedHat_7 PCs. The master node connects to two networks(Internal and Internet). I used to utilizing NAT to provide Internet service for all the computers. For ...

Am I understanding right about linux bonding and switch?

If there are one server and one switch, if the switch dies, service on the server down. So there are normally two switches, and the server should be connected to the two switches, therefore there ...

iptables block IP for x hours not working?

On my Linux server, I want to ban IPs that access certain ports for 24 hours using IPtables. For this, I use the following IPtables rules: # Check if IP is on banlist, if yes then drop -A INPUT -m ...

How connect a linux box to an azure point-to-site gateway?

My initial attempt was to try to use internet connection sharing and dedicate a machine to front-end the Linux box (just forward lots of ports), but connection sharing doesn't seem to work when ...

centos server with virtual machines parent cant connect out but vms work fine

I have a server centos 6.2, it has several vm's using https://virt-manager.org/ the vms work great, no problems. The problem I have is the parent server cant connect out using any protocol. DNS works ...
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