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.
1,255
questions with no upvoted or accepted answers
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Unassigned secondary IP stuck on AWS Linux EC2
I have a couple of c5.large instances with two network interfaces each, running the latest Amazon Linux 2 AMI as of 2018-03. They used to have 8 IP addresses on each interface, which is now changed to ...
2
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1
answer
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Inter namespace communication over linux bridge
So I have the following scenario:
I have a server with 1 physical network interface. On this server I want to create 2 networking namespaces (NS_NASty and NS_MongoDB). Both namespaces should be able ...
2
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1
answer
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SSH to home network when machine behind router is connected to a VPN via tun0 iface
At home I have a network behind a router. Right now I am sitting in the office.
The router is connected to my ISP and I know my IP. (e.g. 11.22.33.44)
I can ping the IP.
In the router I can enable ...
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Debian 8 - TCP Overflows / TCP Drops
I have recently installed netdata on my Debian 8 server (monitoring software) and afetr installing my Debian 8 server is reporting the below two alerts constantly.
1m ipv4 tcp listen overflows = 37 ...
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256
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LXD external static ip
I'm using LXD for managing LXC containers. I used the "standard" bridged NAT setup up to now. But know I got an additional static ip which is external available. I want to attach it to my container ...
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805
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l2tpv3 tunnel with local ip in vrf (linux kernel vrf)
On a ubuntu host I have two identical ip addresses configured on two interfaces enslaved to two different kernel vrfs. Here they are:
mikle@LabHost:~$ ip link show vrf VRF1401
7: enp3s0f0.1401@...
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How to create a Docker bridge network without NAT, without DHCPv4, and without proxy DNS?
Note 1: as far as I understand the suggested MACVLAN architecture, I cannot use two physical network interfaces with the same MACVLAN. However, in my application I need to have a single LAN/L2 domain ...
2
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1
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129
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when should I raise an alarm if I see dropped packets ( packet_in or packet_out)
I am trying to create a simple anomaly alarm detection by looking at the KPI of my Linux servers. I was wondering when should I flag an alarm if see dropped packets ( both packet_in and/or packet_out)....
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311
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Namelookup issue on Azure using custom Docker container
I'm having trouble with name resolution on Azure using custom Docker container with Web App on Linux.
Name resolution with curl and wget takes 4-10 seconds when using default resolv.conf file in ...
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354
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DD-WRT Iptables Mangle Packets are not marked
I have one problem, even in case the rules are applied without any errors, they don't work
Now my configuration
iptables -A PREROUTING -t mangle -s 192.168.0.113 -p tcp -m multiport --dports 80,...
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399
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nginx webserver flooding NFS with metadata requests
I got a simple AWS cloud using nginx servers (EC2s) and NFS drive to store CMS files (EFS). Amazon has famous credits and I ran out of credits on a very low traffic cloud. After investigating it turns ...
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615
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How can I prevent clients from communicating with each other when setting up and OpenVPN server?
I'm trying to configure my OpenVPN server (Ubuntu 16.04) such that clients cannot communicate with any other device except for the OpenVPN server itself. I've tried removing client-to-client from my ...
2
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4k
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Ubuntu KVM - Can't access network through bridge from guests, no DHCP, no ping
I have a laptop running Ubuntu 16.04.3 LTS graphical (so has Network-Manager et al installed). I think I've got KVM and QEMU installed correctly. When trying to set up a Debian VM from the netinstall ...
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2
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IPTables + Limit module: Why doesn't limit-burst get completely used?
Long time reader, first time poster.. yada yada yada..
Anyways, I am hopeful someone out there has some extensive iptables/netfilter LIMIT or HASHLIMIT module experience and explain the behavior I'm ...
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What problems can the use of TOE cause?
What problems can the use of TOE cause?
As known, TOE (TCP offload engine) offloads the processing of TCP/IP stack from CPU to the NIC: https://wiki.linuxfoundation.org/networking/toe
CPU has more ...
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2k
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lftp connection hanging (instead of failing)
i have an automated script that uses lftp to connect to a server and download a file. i've had the script run successfully quite a few times (so i know in theory it works). recently, i suspect we ...
2
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1
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441
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Can Linux queueing discipline solely to lower latency? Can it be disabled?
i'm learning about queueing discipline as part of tuning the network stack on our carbon-c-relay cluster. My understanding is that the queueing discipline layer exists solely to lower latency and ...
2
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544
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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
...
2
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0
answers
150
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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 ...
2
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1
answer
4k
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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 ...
2
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0
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2k
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OpenVPN can't ping LAN devices
I have a setup pretty similar to this except the LAN clients are behind a DHCP relaying router. The outermost router forwards traffic to the OpenVPN server on port 1194 and I can connect clients ...
2
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1
answer
4k
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Routing between OpenSWAN / IPSEC tunnels
I am trying to connect multiple Amazon VPCs (across regions) together using OpenSWAN and Amazon VGW's. The router instance can ping to hosts in both VPCs, and traffic is attempting to cross the router,...
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How do I prevent Router Advertisement from updating my IPv6 route?
I want to send large IPv6 packets without fragmentation in RHEL6.5. I am using this command to test:
ping6 dest_ip -s 8952 -M do -c 100
This is what I have tried:
Set MTU:
ifconfig eth0 mtu 9000
...
2
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answers
574
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CoreOS docker host cannot access containers by IP; other computers on LAN can
We have a problem that our server hosting our containers are unable to access them with their IP, while other computers on the network can. We've got the following setup for our LAN:
A server ...
2
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1
answer
3k
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How to use HAProxy in load balancing and as a reverse proxy with docker?
I am using HAProxy docker image to load share between multiple similar containers. It's working fine if I am using a single address like web.abc.com to query only the API containers, which is mapped ...
2
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1
answer
991
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Does IPv6 equal cost multi-path routing work on Linux Kernels?
End goal is to get per-packet ipv6 udp load balancing by having multiple servers with the same /128 set on the lo interface. To start, just trying to get it to work with static routes, then will start ...
2
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0
answers
85
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Iptables don't load balance
I have consulted multiple tutorials to achieve load balancing over two internet connections. However, all traffic continues to get routed over the default route with the lowest metric, and I can't ...
2
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270
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How to upgrade Ubuntu to 16.04 LTS and not lose network access
When I upgraded one of my servers to 16.04 LTS I had to adjust network configuration (I use interfaces file) and use the new network interface name. I was lucky that the server runs in a VM and I ...
2
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1
answer
2k
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TCP retransmission delays - lost acks
Maybe somebody will be able to help me out with this. I'm trying to find out if there is anything that can be optimized server-side to reduce delays in case of packet loss.
Environment: Windows 2012 ...
2
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571
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what makes RPS different from IRQ balance
i was reading about RPS[Recieve Packet Steering] and how it makes Packets distributed on different cpus.
I believe IRQbalance also does the same thing by distributing interrupts on different cpu.
...
2
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89
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Debian-Server: Incoming SSH/PING/TELNET/... works - outgoing does not
I've mentioned a strange behavior of my linux-system:
After rebooting the system I can connect to it via SSH and the server responses to PING. But the server itself can not ping any other servers.
# ...
2
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answers
156
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Dynamically enable IPSec for IP connections between many servers
For a given list of internet server (example):
S001 - 45.67.89.12
S002 - 67.78.90.34
S...
S999 - 98.76.65.54
I want to talk from each server to any other server to any TCP service using the public ...
2
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answers
507
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What would cause named to send out hundreds of bogus responses?
My DNS server running RHEL 6.6 is actively sending unsolicited DNS responses to a couple of IP's. By unsolicited I mean that there is no incoming request from the external IP, the DNS server seems to ...
2
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0
answers
431
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HTTP DELETE timeout between Nginx and Application
We're facing a really weird error using HTTP DELETE, the symptom is occasionally the user gets a 504 (timeout) error in the browser.
The requests flow through the steps described below:
Browser -> ...
2
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0
answers
40
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How are kernel networking settings handled in OpenVZ containers?
I’m a little confused on how containers handle networking. For our normal systems, we’re enforcing things like Disable Source Routed Packet Acceptance, Disable Send Packet Redirects, etc. We usually ...
2
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0
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1k
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Samba connection fails from OS X
The server is running Ubuntu 12.04 and Samba 3.6.3. Windows users can mount their shares without problems, using the path \\my_server.com\username and account \username.
However, when I try to ...
2
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0
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421
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How to write firewalld rule with rich language
How can I write a rule for firewalld using rich language which restricts packets from a particular port and particular protocol. For IP tables I wrote a rule like:
firewall-cmd --permanent --...
2
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1
answer
85
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Simulate 2 clusters in the same network
I have 4 pc´s and another pc, which will act as a proxy, all being in the same network: 172.16.96.0/20 . I can ping between each other. But, I want to separate them into two groups. That is:
pc1 is ...
2
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215
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how to divert incoming all tcp packets at eth0 to socks proxy and to eth1 of same host?
I have a three ubuntu linux hosts.
host 1,host 2 and host 3.
I want to pass data from host 1 to host 3 via host 2.
But specifically I want to pass all incoming traffic of host 2 to socks proxy then to ...
2
votes
1
answer
857
views
ModSecurity rule to not scan URI
I am having difficulty creating a new mod security 2.5 rule.
My deployment:
Apache server, Setup as a reverse proxy.
(so the apache webserver __does not_ host the website. Instead, I proxy the ...
2
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0
answers
1k
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How to use iptables or IFB to mark incoming traffic by device?
I'm trying to use iptables to mark incoming packets based on the device where those packets arrived (rather than their originating IP address or port etc), but haven't found a way of getting this to ...
2
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1
answer
2k
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Linux clients can't connect, server and TCP Windows Size / Timestamps issue
We have a problem that a number of clients (all linux Ubuntu) are sometimes not able to connect to a remote server over SSH. If the problem occurs, Windows clients don't have that problem and can ...
2
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0
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221
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Configuring openldap/PHP LDAP against "signed" LDAP connections with Active Directory
This may sound like a stupid question, and maybe it's already been answered, but I can't find a definitive answer anywhere, so I thought I'd ask.
When someone enables "Domain controller: LDAP server ...
2
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0
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558
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Separate L2TP/IPsec VPNs with dynamic VLAN assignment
I am working on a Linux (Debian 7) VPN concentrator for different kinds of remote access. One of the offered protocols is L2TP/IPsec because of the client availability. I am using xl2tpd which in turn ...
2
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0
answers
97
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IPsec - strange behavior
I have set up site-to-site ipsec connection between linux(debian) and mikrotik router.
The tunnel is up
linux configuration:
config setup
interfaces=%defaultroute
keep_alive=60
...
2
votes
1
answer
6k
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Adding subnet to a vsphere with single vcenter and esxi host
Let me start of by saying that I do not specialize in networking, I am in the process of adding additional VMs to a testing environment and wanted some recommendations.
In this case I am running a ...
2
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155
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PIV authentication on redhat
I'm looking for a solution, or set of technologies, (etc) - for setting up a mixed (win 7, rhel 6.5) network with centralized login using smart cards (PIV).
I know that this is possible using a ...
2
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1
answer
943
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Host doesn't send ACK-SYN packets for transparent proxy
I am setting up a transparent proxy using haproxy, the setup works without the 'source 0.0.0.0 usesrc client' line. When I add that line in, the endpoint is called from the original client's ip ...
2
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1
answer
709
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Is the ethx mac address of a VM the same as the mac address of the corresponding tap interface?
I have a single node openstack install on an ubuntu machine. For some reason that I cannot figure out, the linuxbridge is dropping packets from this VM. My iptables seem to be fine (atleast as far as ...
2
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0
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2k
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access tap interface in network namespace across machines
I want to be able to access services running on a TAP interface within a namespace from outside the machine where it is running. I have setup that looks like this -
VM1/Machine1
+eth0 : Public ...