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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1answer
37 views

IPTables Configuration to allow all connections, only close/deny once data is sent

I'm looking to set up my IPTables firewall in such a way that: Any new connect() is accepted Once data is received: If the destination port is on a whitelist, continue allowing the connection and ...
1
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2answers
126 views

How to setup a netem box

I'm trying to simulate different network condition based on factors such as latency, bandwidth and so on. I found that Netem is the best way to simulate different network condition. So my desired ...
2
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1answer
56 views

Can Linux be made to honour IPv6 Route Advertisement preferences?

Bottom Line Up Front: I can't get a Linux box receiving RAs to use the RFC4191 "Default Router Preference" value to prefer higher-priority routes. Instead, whichever default route it learnt first is ...
0
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1answer
26 views

CentOS: How to create a default route after server starts

I'm using CentOS 6.7 on Proxmox KVM. Now I would like to get my network-connection working. This is my config: Now I have to perform ip route add 89.xxx.xxx.1 dev eth0 and ip route add ...
0
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1answer
64 views

Unable to access Node Server from external network

I have a VM with two public IPs. I have installed OpenStack controller node on the VM. I have access from the external network to Horizon and Keystone service running on apache2 web server on ports 80 ...
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0answers
12 views

Capture no-modified packet with iptables

I have a user-space program in which I process packets. I send them there with help of iptables. The problem is that I capture not original packet but modified. I have wlan0 interface up with access ...
0
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1answer
83 views

PFSense IPSec and NAT

Due to bad design and hosting provider constraints I have a network where I don't control the router. Our network: 172.16.0.0/12 - LAN x.x.x.0/24 - WAN (Router is connected to the switches, we have ...
0
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1answer
108 views

CentOS port forward

I have the following situation: Internet ----- Server ------- virtual machine (kvm) public ip 192.168.122.12 x.x.x.x I need to make service on the port 3333 ...
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0answers
27 views

keep ossec iptables rules after restarting OSSEC

I have 6 OSSEC installations (5 agents + 1 server, all Debian 8) all configured to block repeated offenders using iptables from 10 minutes to 1 month. I have the need to restart one or more of the ...
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0answers
31 views

OpenVPN connect to OpenVPN client network

OpenVPN Server Ubuntu 14.04 In Digital Ocean (Public and Private interface) OpenVPN client Ubuntu 14.04 I can't SSH from Server to client via VPN connection. Ping works fine. Tunnel is up. Followed ...
0
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1answer
24 views

Change name of the internet network service on CentOS

If I try nmap to my server (CentOS 7), I get something like this: $ nmap myserver.com Nmap scan report for myserver.com (1.2.3.4) Host is up (0.93s latency). Not shown: 998 filtered ports PORT ...
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0answers
41 views

What is the difference between arp_ignore and arp_filter?

What is the exact difference between the arp_ignore flag and the arp_filter flag defined in syctl.conf in Linux? Both seems to serve the same purpose.
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1answer
36 views

How are IP packets routed from LAN to WAN? [closed]

I have OpenWRT set up on a router, with a wireless client connected on the LAN, and connected to another network on the WAN. wlan1 is bridged on the br-lan interface, and typically forwards to the LAN ...
1
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0answers
33 views

Which virtual/software switches support meter table (QoS) in OpenFlow v1.3 [closed]

Does anybody know which virtual/software switches support OpenFlow v1.3 meter table QoS feature?
3
votes
1answer
61 views

fallback route to drop packets if output interface that is NATed to goes down?

Background: I establish a connection to a 3rd party VPN and NAT packets marked as part of a particular cgroup (in order to selectively run processes through the VPN or not) to the 3rd party's VPN tun ...
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0answers
9 views

How can I drop packets in SnabbSwitch on the same interface

Can I have the following setup using SnabbSwitch ? https://github.com/SnabbCo/snabbswitch traffic packets -> eth0 -> SnabbSwitch (eg...drop half of packets) -> eth0 -> binded software (nginx, apache.....
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0answers
82 views

configure host to use private DNS server when result is not found?

Is there a way to configure a Linux host to resolve hostnames using a primary DNS server but if the result is not found, resolve using a secondary DNS server? The reason is that I have some hosts ...
0
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0answers
12 views

CentOS VPS IP Address - Removes Automatically - ISPConfig

I have a CentOS VPS, CentOS 6.5 is installed, I have added 4 ip address as - 192.168.1.1 192.168.1.2 192.168.1.3 192.168.1.4 The problem is, the ip address xx.1.4 is getting removed automatically ...
-1
votes
1answer
70 views

bad localhost resolution on linux [closed]

$ dig @127.0.0.1 localhost $ dig @127.0.0.1 localhost. ;localhost. IN A ;; ANSWER SECTION: localhost. 604800 IN A 127.0.0.1 ;; AUTHORITY SECTION: localhost. 604800 IN NS ...
0
votes
1answer
43 views

Why are ICMP packets not captured on the target interface?

I have a network setup as in the picture: The central box is a gateway (Ubuntu 15.10) which relays the packets betwen the various networks (only one is shown on the picture - lan0) and Internet. ...
1
vote
0answers
27 views

iperf actual send rate always lower than the expected target bandwidth until some equilibrium reached. Why?

I did an UDP iperf 2.0.5-Ubuntu test between two VMs on the same hypervisor. As can be seen in the iperf output below I started my first test with "-b 686M" flag. However, iperf reported that it was ...
1
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0answers
27 views

CentOS 7 ifup scripts actually doesn't change interface name

It has occurred to me that in CentOS7. While one can still specify interface names in sysconfig, the ifup scripts actually does not change interface fact "via ip link set dev ${DEVICE} name". For ...
0
votes
1answer
45 views

iptables counters in NAT table and state NOT NEW

I read everywhere that it is dangerous to do traffic filtering in the nat table because the nat table is only consulted for connections whose state is "NEW" (later packets bypass the table). Does it ...
0
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0answers
36 views

iptables (nth) load balance, connect failed: Connection refused when many request

I try to use iptables as load-balancer using round robin scheduling. Block Diagram My itables configuration on 172.18.3.190 like this : *nat :PREROUTING ACCEPT [42:7044] :INPUT ACCEPT [26:4290] :...
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0answers
38 views

What rules do i need to allow ipsec in iptables firewall?

I have a server sitting on a private subnet behind a iptables firewall. On that server I am planning to create site to site VPN to Amazon VPN. I am not sure what rules do I need to put in my iptables ...
1
vote
1answer
78 views

How to block all domains except few in BIND DNS?

I came across solutions for blocking selected DNS resolutions by creating block zones. But how would I allow certain sites only and blocking all others in BIND?
1
vote
1answer
81 views

Cannot access Debian smb share from Windows 7 64

This is an old problem, an in my experience the connection between windows and samba is unstable and different for every implementation. Sometimes it works, sometimes it doesn't, often without any ...
6
votes
2answers
291 views

Accelerating VPN speed using multiple connections

I have set up a VPS with openVPN running on centOS. The VPN works, but it's too slow. Is there a way to speed this up using open multiple connections like IDM or aria2? I'm using openVPN but I'm ...
1
vote
1answer
42 views

Compare two Linux servers for network configurations [closed]

Some guys did initial setup of servers and they moved on now we see lot of network issues on new servers I want to find a way to compare servers ( New vs old ) to check any specific tuning which was ...
0
votes
0answers
59 views

Firewalld blocking Squid

I have a serious problem here with Squid and Firewalld in Fedora 23. When I activate firewalld, I can not access the proxy I created, it returns a "Connection refused by the proxy server", but when I ...
0
votes
1answer
59 views

QOS with iptables and tc with unstable WAN

I have a router/gateway under Linux, I want to add some QoS to reserve bandwidth for a specific flow. This can be done with iptables/netfilter and tc, but all examples start from the fact that you ...
0
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2answers
37 views

Binding conflict with iptables rules [closed]

I m developing a server in C which bind on a random port I m afraid that the choosen random port could conflict with iptables rules. I mean if the choosen port could be already exist in iptables as a ...
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votes
2answers
77 views

Multiple NIC same subnet [closed]

I have a setup as shown in the image. I know it is insane but i have to work on this configuration only. It is basically an ubuntu server acting as a router with 4 interfaces. 3 of them (eth0, eth1 ...
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0answers
57 views

Using LINK_REQUIRED parameter with wicked

I'm running SLES 12 and trying to configure network interfaces; this is my first experience with wicked. I'm using "ifup" to up the ethernet devices. I ran into an issue of not being able to ifup the ...
0
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0answers
17 views

Add second openvpn server for one segment subnet with able to see each to each of clients?

There is openvpn server for one segment subnet, client to client visibly, and static assign private IP addresses. But this server may be is off. How add second server for solve minimum time off ...
0
votes
1answer
25 views

Remotely remove MAC table entry from Juniper router

In our colocation we have multiple linux servers with a public uplink connected to a juniper MX40 (that we can not control) and an internal link each. Sometimes we get incoming UDP flooding ...
0
votes
0answers
62 views

Added OVS bridge in /etc/network/interfaces and then rebooting made Ubuntu machine lose its connectivity

I am trying to define an OVS bridge br0 in /etc/network/interfaces file(ubuntu 14.04). The /etc/network/interfaces file is as shown below: auto breth0 allow-ovs breth0 iface breth0 inet static ...
-1
votes
1answer
191 views

Setting up DNS server to resolve request to domain “abc.com” to its own host

I have a server with the public ip-address (lets say) 198.20.30.40 I am trying to setup a DNS server on this host so that I can resolve all request to "stackoverflow.com" being made to get resolved ...
0
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0answers
53 views

How to set multiple client IPs on a single machine mapped to multiple public IPs on a single OpenVPN server?

I have a properly working setup of an OpenVPN server in which: Each client has its own VPN IP address Each client IP is tied to a public IP Client configs are separated by CCDs So far, a client is ...
0
votes
3answers
78 views

Assigning multiple IPs to the same machine with one interface

I have a server with a single physical interface eth0. I intend on running VMs on this server. To that end I have an IPv4 block which is routed to said server. What I'm trying to achieve is to spin-up ...
0
votes
0answers
41 views

arpwatch to listen only to particular network

I deploy arpwatch is our network and it is working fine. But it is not doing exactly what i need. Here is what i need ... i want it to listen to one particular network ... for example on ethernet 0 it ...
1
vote
1answer
170 views

Can't connect to remote centos 7 install from at least one host

Edit: It would appear that the problem has somehow magically disappeared after leaving everything alone for almost 24 hours. After just sitting down to look into it further, I notice that my website ...
1
vote
0answers
55 views

IP Multicast between Windows and Linux

Our team is developing linux/windows applications for our network that are talking to each other via multicast. We had it working when we only had linux boxes on the network, but we recently added a ...
0
votes
0answers
25 views

Can not connect to ssh over IPsec VPN

I am trying to reach a machine via an ike IPsec (shrew soft) VPN connection. I can ping the remote machine: $ ping 10.3.6.10 PING 10.3.6.10 (10.3.6.10) 56(84) bytes of data. 64 bytes from 10.3.6.10: ...
0
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0answers
46 views

What happens when connecting to port in TIME_WAIT state?

I'm trying to understand the effect of TIME_WAIT on subsequent TCP connections. I understand how TIME_WAIT behaves when net.ipv4.tcp_tw_reuse = 1, as explained by this answer. But what happens when ...
0
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0answers
39 views

IP Tables, does it really need those rules?

I am just starting with IPTables, and I am wondering if I really have to create so many rules for a simple setup: DMZ (Reverse Proxy) port 80 + 443 Frontend Subnet: Apache Webserver The Reverse ...
0
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0answers
53 views

TCP sockets dying on LTE

I have about 25 audio streaming clients built on an i.mx6 arm platform, running linux version 4.3.0-rc2-00019-gbcee19f-dirty #36 SMP Tue Feb 9 15:27:51 EST 2016 armv7l I find on two specific units ...
1
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0answers
29 views

IP Aliassing - Multiple Public IP Address [closed]

I have a problem with IP Aliassing. I want that all IP addresses have ism traffic but it does not work except to redirect eth0 with iptables DNAT and SNAT which is ineffective. auto lo iface lo inet ...
1
vote
0answers
28 views

rx_queue value in /proc/net/udp grows to twice the SO_RCVBUF value

When using an SO_RCVBUF of 10485760 (which is also the current limit as stipulated by sysctl's net.core.rmem_max setting, and sending UDP packets faster than the receiving side is able to handle, the ...
0
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0answers
25 views

tcp receive buffer size min value seems not work

I tried to increase tcp min receive buffer size to 87380, so in my test it would OOM quickly with a little connections. net.ipv4.tcp_rmem = 87380 87380 6291456 net.ipv4.tcp_wmem = 87380 87380 ...