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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OpenSuse: How to allow an outside network to access the local network?

I want to connect vlans of two separated networks I administer and it's almost complete, Allow me to describe the situation: Network A's firewall is a FortiGate 1000C and the vlan is 192.168.2.0/24 ...
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3answers
64 views

how to monitor network traffic in small office

We have a small office with around 30 systems . We have an internet connection connected to a router , The router is connected to a gigabit switch . All the computers are connected to that switch. ...
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0answers
18 views

iptables, redirecting all ingoing connexion

I have this iptables conf on my linux mint... What does it mean ? Chain INPUT (policy ACCEPT) target prot opt source destination ACCEPT all -- 13.37.42.0/24 ...
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44 views

How to troubleshoot rx_missed_errors?

Migrating from old server to new one, after setting all services, I notice a big dropped rx packets in my NIC: $ ifconfig eth2 | grep 'RX.*drop' RX packets:2059646370 errors:0 ...
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17 views

Spurious retransmission, Dup ACK and HTTP 408

I have a server which serves as sms gateway (using kannel) and have multiple client connecting to it, but recently this one client with their particular IP said that they can't send to my server and ...
0
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0answers
38 views

How to get GPS time in linux from an external server? [on hold]

I am building an application in linux which needs GPS time. But I don't have any GPS receiver. How can I get GPS time from an external server?
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24 views

Restricting ports to application / user

I'm currently working on a platform that will allow other users to run their applications on my platform. Though, we need to be able to restrict this application in terms of RAM, CPU usage, network ...
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0answers
16 views

Bandwidth Policing on Linux gateway - not QoS

I have a linux server providing NAT to a large subnet (/16) using iptables to-destination + multiple external ip's to survive port exhaustion. I've looked at using tc / htb such as here Limiting ...
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1answer
26 views

Time Between successive DNS queries.

Using a PC running Ubuntu 14.04. I'm testing web browsing using a very low speed and low data rate link. My system is congested with DNS queries (and other types of packets like TCP re-transmission). ...
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0answers
19 views

How can I bridge an HTTP server from an interface to another in Linux?

In a Linux server I have an HTTP server that's available at eth1 with ip1, and I want to make it available to the network in eth2 with ip2. How can I do this? Example: I have an http server on ...
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1answer
21 views

Static ip routing in Mac OS [closed]

OS X machine with x2 NICs connected (en0 and en1). en1 is the default interface and connection to the internet via gateway 192.168.1.254. My IP is 192.168.1.65 en0 is a private connection with ...
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24 views

Do my iptables do what I need? [closed]

I'm an ecologist attempting to write some apps to run unique IR cameras and manage a couple of computers by learning enough linux and networking to get by. I'm not well versed in networking or linux. ...
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1answer
32 views

Linux: nslookup and dig resolve $HOSTNAME, but ping doesn't

In our private network we have a Consul service discovery server (10.241.232.14) that provides a DNS interface (port 8600). We would like to set our common DNS servers to forward some queries to the ...
0
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0answers
18 views

Gateway to internet on CentOS 6

I have 2 CentOS 6 linux servers say hostnames cent001 and cent002 cent001 has 2 Nic's 1 Bridged and 1 Nat cent001 is able to ping google server 8.8.8.8 with the help of bridged NIC cent002 has only ...
0
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0answers
16 views

dhclient vpn_tun0 causing internet disconnect after upgrade to ubuntu 15.04

A few weeks ago I installed softether vpnclient on my ubuntu 14.04 laptop and vpnserver on an ec2 instance. The server uses softether secureNAT and the softether dhcp server. My client produces an ...
1
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0answers
22 views

Get Original Destination Port From iptables

I would like to create a local server that acts as a proxy for all trafic, but how would I determan the original ports when using iptables to rederect the network traffic. I need this for when the ...
0
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2answers
49 views

Different subnet mask on router and DHCP server

ran into something funny today and am still scratching my head on why this happened. I was trying to increase the number of ip addresses available from my dhcp server by changing the netmask from /24 ...
0
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0answers
18 views

Problems with route table with two nics on different subnets

I have an Ubuntu server with two NICs on two different vlans. Both nics are able to reach the internet. The server is an Ubuntu MAAS machine and therefore has pxe and dhcp and such. The DHCP server ...
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0answers
22 views

Unable to Mount a directory on linux server :- Error ICMP host unreachable - admin prohibited, length 68

Folks , I have two linux server. I want to mount one directory /symantic of one file system to another. I am able to ping , i am able to do telnet from each other. I have checked port 2049 which is ...
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2answers
58 views

How to get a client IP address from a specific network?

I have a condition to filtering IP address from client, and I just have their IP network like this 1.1.0.0/17. If some client from this network will be filtered as special user on my website. And I ...
0
votes
1answer
45 views

Trouble with network (ping, route, gateway)

I have a server running CentOS 7 and I connect to it by ssh. SSH takes a little bit to connect compared to the other server I have setup. This server has 2 ethernet ports (1 motherboard and 1 card). ...
0
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0answers
10 views

VIP (Pacemaker) - Second VIP on host stops responding after random period of time

I've got a host that was recently installed with Pacemaker, 3 physical interfaces, on two of which a VIP has been setup, VIP1 appears to be working flawlessly, while VIP2 becomes unavailable after a ...
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0answers
16 views

OpenVZ: Node iptables doesn't append rules

I want to make a set of rules on iptables inside of a node, but it seems that the iptables isn't appending all the rules or somehow and kick me out everytime I run the following script (I'm using this ...
0
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2answers
12 views

Modsecurity rule to not scan URIs

Good Morning, I am currently on creating a new mod security 2.5 rule. My deployment: I have an Apache server in reverse proxy mode. This Apache server does not host the websites. Instead, I proxy ...
2
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1answer
22 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 ...
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0answers
8 views

Suse11 default gateway lost after interface restart

Doing some test on a SLES 11 SP2 virtual server I noticed the default route was lost after restarting the related interface: # netstat -rn Kernel IP routing table Destination Gateway ...
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2answers
19 views

IP from multi gateway, openvz debian

I have a problem with network in my dedicated server. I have a host: ip 188.60.240.71 netmask 255.255.255.128 gateway 188.60.240.1 broadcast 188.60.240.127 network 188.60.240.0 I order additional ...
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0answers
44 views

Fail2Ban / IPTables does not block IPs

My server : Debian Wheezy 7.8, Postfix/Dovecot, Fail2Ban/IPTables I've postfix attacks : /var/log/mail.warn Jun 12 08:03:45 myserver postfix/smtpd[8325]: warning: ...
0
votes
1answer
12 views

Troubleshooting Curl Timeouts

I run a SaaS monitoring service. Our standard integration example is to make a curl request to a special URL we provide. We have an intermittent issue where a user is hitting a 10 second curl timeout ...
0
votes
1answer
53 views

How to assign multiple IPv6 Alias addresses to one network interface

I have an IPv6 Range which i am trying to assign on a centos6 server. I have updated my below files for IPv6 configuration: [root@test ~]# cat /etc/sysconfig/network NETWORKING=yes ...
38
votes
6answers
4k views

How can you tell what a server actually does? [closed]

I've been handed 3 Linux boxes, 1 front facing with apache on it and another 2 which, as far as I can tell, don't do an awful lot. All running on Redhat. The question is simple: How can I tell what ...
0
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1answer
24 views

REDSOCKS goes 'out of file descriptors' when trying to redirect all outgoing (TCP) traffic from my Linux machine

I'm trying to redirect all outgoing TCP traffic from my linux box to the remote SOCKS5 proxy server. Currently I'm using the following rule in the OUTPUT chain: sudo iptables -t nat -A OUTPUT -p tcp ...
1
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1answer
48 views

Difference between “genmask” and “netmask”?

In the output of route -n on Linux, you get something like this: Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 0.0.0.0 10.0.0.1 ...
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0answers
14 views

Determine if Reverse SSH tunnel is being used

I have a client machine that makes a reverse ssh connection to my ubuntu server. On my server I can see the connection when I run: netstat -nat With the connection open, Users can access the ...
1
vote
1answer
51 views

if secondary dns server is down ubuntu can not resolve

I am experimenting with two local DNS server. When I take down the second (or the primary) dns server, I can not resolve any domain name. Using host command or nslookup I get time out error : ...
0
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1answer
32 views

iptables hashlimit memory usage: What is the difference between --hashlimit-htable-size and --hashlimit-htable-max

I'm looking to use iptables hashlimit to limit abusive web crawlers, much like this question is trying to limit ssh bruteforce scans. Every once in a while they hit an inefficient code path on our ...
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0answers
54 views

Create Bridge interface on linux board

My current configuration and topology look like below: +++++++++++++++++++++++++++++++++ +++++++++++++++ | Linux Board eth0 | | Switch | | with openWRT ...
1
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0answers
16 views

Ubuntu server drags network speed down to 10Mbps [migrated]

I'm running an Ubuntu Server (14.04) on my home network. It acts as a OpenVPN server (Bridged, not routed) and it runs one Virtual Machine (KVM, through a bridged virtual network device (br0)). The VM ...
0
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2answers
42 views

Clear TCP sessions

I am trying to use iptables to reject packets as well as reset the TCP connection. My rule is: iptables -I FORWARD -p tcp -s 10.0.0.10 -j REJECT --reject-with tcp-reset If 10.0.0.10 is SSH'ing into ...
0
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0answers
24 views

Linux router showing packet loss

I have two linux boxes that are using a third box as a router. Packets flow normally. BoxA(10.0.0.10) -> (10.0.0.20) RouterBox (172.16.50.20) -> BoxB(172.16.50.30) When I run mtr from BoxA to BoxB the ...
0
votes
1answer
37 views

forwarding ping using ip route [closed]

I have a Linux setup which consists of two interface. A local LAN interface and virtual interface. ETH0: 150.10.15.194 PAN0: 192.168.255.209 I would like to set rules that route all ICMP echo ...
0
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0answers
76 views

reducing bufferbloat in linux web server

I'm looking for all the buffers I can tune in linux as well as their order of operation. On the server, nearly all operations are run over the TCP protocol. I want to eliminate bufferbloat to improve ...
0
votes
2answers
55 views

SSH Connection through a Reverse (Remote) SSH Tunnel

This is the setup I have : a Linux box A inside a LAN behind a firewall. a Linux server with a fixed IP address that is accessible from the internet. I want to be able to connect to the Linux box ...
0
votes
0answers
12 views

bird4 - OSPF not learning/distributing /32 routes in hub-and-spoke topology

in my hub-and-spoke setup all the boxes are happily exchanging local LANs routes through bird4/OSPF. The links between the hub and the spokes are VPN p2p links and I need the address of every spoke's ...
0
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0answers
25 views

Changing value of tcp_fin_timeout in unix machine

I was looking at this article in which they have mentioned how to increase two property for better performance of application if we see lot of TIMED_WAIT connections My question is: if I modify ...
1
vote
1answer
70 views

“net.c:577: sendmsg() failed: Operation not permitted” in dig Output

I am running Bind 9.10.2 version on CentOS 6.6 machine. While running the dig command, i am getting "net.c:577: sendmsg() failed: Operation not permitted" notification. dig utility is giving me an ...
0
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2answers
183 views

Stop China from connecting to my Google Compute Engine server

My company has a Google Compute Engine server hosted in North America. We get so many Chinese IP addresses sending requests to port 11 that it is costing us money for the ingress. Our firewall blocks ...
6
votes
1answer
138 views

Is it possible to process millions of datagrams per second with Windows, using a vendor agnostic API? [closed]

I am investigating if I can implement an HPC app in Windows that receives small UDP multicast datagrams (mostly 100-400 Bytes) at a high rate, using a dozen or up to maybe 200 multicast groups (i.e. ...
1
vote
1answer
39 views

Routing issue on Linux with Mobile Broadband

Note: This is a "cross-post", I asked this same question on "superuser" StackExchange site, but without obtain any answers, just a comment (now curiously disappeared). I've thought this site is ...
8
votes
0answers
84 views

SynProxy can not return syn ack packets with asymmetric dual bridge topology

I have a asymmetric dual bridge topology as shown below when i connect from 172.16.11.5 and 172.16.10.6 with ssh but i can not connect because of SynProxy. ------- ...