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
78 views

Trace route to specific page on a website [closed]

If I can access a site (ie: serverfault.com) through my proxy/firewall, it means that it will allow all it's subdirectories (serverfault.com//)? I can access the website site.com/ but it returns me ...
2
votes
1answer
302 views

Rate limiting udp packets destined to a linux machine

Is there any way to ratelimit udp packets destined to my linux machine? I am sensing some udp packet drops destined to my machine. Was there any default udp rate limiting conf in linux? I have seen ...
1
vote
1answer
54 views

How to set up custom multicast address

What would it take to setup a custom made multicast ip address in the network? Machines are linux. Let's say I want to have a multicast address with only some machines from the network as group ...
3
votes
2answers
2k views

Linux adds the wrong default route

For some reason my Centos 5.9 Linux 2.6.18 x86_64 wants me to have two default routes. Whenever I reboot the server, my routing table looks like this: [root@server1 ~]# route -n Kernel IP routing ...
0
votes
1answer
73 views

Network configuration for linux server

I had some troubles with a Linux server after being restarted. I can log to the machine but I cannot remotely access this machine via ssh client: ssh -v -v -v root@IP gives me connect to host IP port ...
0
votes
1answer
294 views

Can't reach multi-homed Ubuntu from different subnet

I have a multi-homed Ubuntu 12.04 server. I have two network interfaces connected to two different IP ranges. 2: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen ...
2
votes
3answers
3k views

How can I achieve OpenVPN client routing without NAT on Linode

I've set up an OpenVPN network, and it is working properly in the sense that I can access the inner/LAN machines from the remote client. However, my problem is that all traffic from the remote ...
10
votes
3answers
15k views

What is the correct way to open a range of ports in iptables

I have come across articles advising for the following: iptables -A INPUT -p tcp 1000:2000 -j ACCEPT And others stating that the above will not work and iptables only supports multiple port ...
0
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0answers
264 views

Is there any way by which I can capture the wifi probe requests without using monitor mode?

For some reason, keeping the wifi interface in monitor mode on my machine is crashing it(its a raspberry pi, I'm assuming its crashing because of the amount of traffic being intercepted, but lets not ...
4
votes
1answer
130 views

Ban an IP when the server received an amount of data from it

What I need : There are many result for adding a drop rules by an amount of request per laps of time, but I need to drop by received byte count from a particular address over a period of time. ...
4
votes
3answers
423 views

In Linux, how can I automatically assign an IPv6 address to an interface based upon its IPv4 address at boot time?

On a CentOS 6 machine, I have a server with 2 NICs, eth0 and eth1. eth0 has address 192.168.0.1. I would like to create a script that parses the IP address of eth0 and assigns a similar-looking IPv6 ...
3
votes
1answer
534 views

Split tunneling through two VPNs simeltaneously

I want to run two OpenVPN client instances on an Ubuntu Server 14.04. I have both .conf files that can work independently (both are set to different interfaces - tun0 and tun1). I want to run both at ...
1
vote
1answer
212 views

How to exclude LAN traffic from IPSEC policy

I am trying to replace a Firewall/VPN appliance (Snapgear SG300) with another (Mikrotik RB951G-2HnD). My current router works, but, for the new mikrotik router, when I add the phase 2 tunnel, I can ...
1
vote
1answer
86 views

specific machines on subnet randomly lose connectivity, but the rest of the network is fine

Every physical machine is connected to a cisco switch and is on the same network 192.168.1.0/24 Every server I have is running Centos 6.5. A couple run KVM with a bunch of virtual machines. Most of ...
0
votes
3answers
217 views

Linux (Ubuntu 12.04) sending ARP requests over single interface

I have a system with custom hardware hooked up to 2 different ethernet ports on the same system. The interfaces are configured on the same subnet because the hardware (FPGA-based) has a hardcoded IP ...
0
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0answers
67 views

Policy routing UDP traffic

this should be a quick one. I have not found any documentation addressing this topic. I have set up some policy routing on my raspberry, but it seems like UDP traffic is completely ignored. Some rules ...
1
vote
0answers
368 views

Shorewall redirect rule only working for some hosts in the same network

I'm trying to use Shorewall's REDIRECT action to intercept traffic destined for the firewall's port 514 (TCP and UDP) to port 5000 (also TCP and UDP), while also allowing direct traffic to the latter ...
4
votes
4answers
605 views

One second delay before tcpdump returns packets

Using Ubuntu, I'm trying to sync tcpdump sniffing with self-identifying "pings" from a client device. The problem is that getting precise starts and stops is made difficult by what looks like a ...
0
votes
1answer
630 views

Remote jmeter-server error while getting the results back after some time

I have a question, I'm using jmeter from my pc that drives a jmeter-server that is installed on a RHEL5.8 my version of java is : [jmeter@sem-osb logs]$ cat /etc/redhat-release Red Hat Enterprise ...
0
votes
0answers
93 views

muliple ssid's on same interface

I am working on centos6. I have 1 wifi interface. Can I create a virtual interface and create an adhoc network with it (my 'real' wifi interface is already connected to another ssid). This is what I ...
1
vote
1answer
793 views

Adding a whole IPv6 /64 block to an network interface on debian

I tried adding a whole IPv6 (/64) block to an interface using ip route add local 2001:41d0:2:ad64::/64 dev lo like described here on my Debian server, but I seem to be missing something. If I ping ...
1
vote
0answers
109 views

Can I route traffic destined for a local interface out another interface?

I'm trying to set up a testbench for a transparent device (called TD from now on). The goal is to make sure it forwards and logs correctly. I need to use just 1 machine + the TD in the test bench. ...
2
votes
1answer
106 views

iptables: does a scanner knows if you DROP packets?

I know how REJECT and DROP chain works. But, as I read here REJECT vs DROP when using iptables, user Dagelf said that the server still replies with TCP SYN/ACK. Does the scanner knows that a packet ...
2
votes
0answers
36 views

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 ...
1
vote
0answers
187 views

Massively large number of packets dropped by interface

I have a virtual machine on ESXi 5 acting as a firewall for a PBX, it is running vyatta. When I run tcpdump on any interface, I get some ridiculous numbers! e.g. 4 packets captured 402 packets ...
1
vote
1answer
976 views

WMI: wmic linux agent query error: NTSTATUS: NT_STATUS_ACCESS_DENIED

Myself new to wmic and keep trying for a long time with default agent query approach. wmic is linux based WMI tool to talk to windows WMI agent. While trying to fetch data with wmic from nt(win7 with ...
4
votes
2answers
580 views

what does `pipe <number>` mean in `ping` output?

While running a test to diagnose some alleged network problem, I got this output from ping: --- r01c01b11n02 ping statistics --- 30000 packets transmitted, 29995 received, 0% packet loss, time 6309ms ...
0
votes
1answer
126 views

Software for emulating networks and NAT

I am working on a software that I need to test with different types of NAT, and I would like to set up a test environment I can reconfigure in different NAT modes. I would like to have: ...
2
votes
1answer
389 views

Assign different Hostname to different NIC

I have four network card on my server, I have assigned each with an specific IP now I want to set an different hostname for all the interface? What is the difference between setting the hostname in ...
0
votes
1answer
412 views

Is it possible to configure Apache to not listen on port 80 when connecting from localhost

Is it possible to configure Apache to not listen on port 80 when connecting from localhost, but allow the connection on port 80 from an external IP?
3
votes
1answer
660 views

Netstat hangs: why?

Sometimes (not too often at all) when I type "netstat", it takes over 5 seconds to return. While other times is instantaneous. I have been observing this for weeks on my server (CentOS 6.4), but I ...
2
votes
1answer
268 views

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 ...
0
votes
1answer
408 views

Can't connect to 2 different Linux computers via VNC (local network)

I have a problem connecting to Vino VNC server with 2 Linux Computers running Xubuntu. The computers are Based on the ODroid U3 chip which is ARM based. When both of the ODroids are on the same ...
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votes
3answers
1k views

How to find out capacity for network interfaces?

I could get the capacity for the network interface by lshw, but which file in sysfs is this information stored(i.e. which file in /sys/class/net/eth0/device/ directory)? $ sudo lshw -class network ...
0
votes
3answers
106 views

Is it possible to route network traffic according to user ID?

On my Debian system, I'd like one of my users to use a different network interface as their default route for all internet traffic. I know how to use iptables to block the other interfaces, but not ...
0
votes
1answer
2k views

disable a network interface on booting ubuntu

I use ubuntu 12.04. I need to boot with one of the network interfaces 'eth1' down. I tried adding sudo ifconfig eth1 down to /etc/rc.local However it seems the interface is brought up and ...
-1
votes
1answer
139 views

Linux 25 port routing (tunneling/forwarding)

I have: 1) Centos server 1 with postfic/dovecot mail servers IP1 45.45.45.45 (DNS: host1.com.ua) server 1 cannot make outgoing request to 25 port because Internet Service Provider block it! ...
-1
votes
1answer
61 views

How do I close ports in Linux for security reasons (KVM)? [closed]

I am going to set up a KVM virtualization server on CentOS. The host machine and several of the VMs will have a dedicated IP addresses. I'm going to need to close off unused ports and probably ...
2
votes
1answer
3k views

eth0 NIC Link is Down repeating message in kernel log

I've noticed since few days ago that same repeating kind of messages occurs and I positively can say that nothing was intentionally changed (installed/uninstalled) in that period. here's sample of ...
0
votes
0answers
54 views

Pinging to google.com from a particular interface

I am connected to the internet via wlan0(wifi) and also have an ethernet port(not connected to the internet). I am looking for some iptables rule / route addition, which will let me do a ping via eth1 ...
2
votes
3answers
416 views

Which private IP addresses can I use? [closed]

I have a dedicated server where I'm running several web-facing virtual machines on public IP addresses; I pay my hosting provider for each IP. I would also like to run virtual machines with private ...
14
votes
1answer
4k views

Should /etc/hosts contain an entry like '127.0.0.1 localhost myhost.example.org myhost'?

When looking at a variety of Linux and FreeBSD systems, I've noticed that on some systems /etc/hosts contains an entry for the public hostname of the host, but not on other systemst. What is the best ...
1
vote
0answers
876 views

Multicast route setup for multiple interface

Currently I have the below eth5 to receive multicast data for 239.1.1.31. It works. $ ifconfig eth5 Link encap:Ethernet HWaddr E4:11:5B:94:E1:F3 inet addr:10.185.2.2 ...
1
vote
2answers
136 views

How do I throttle network activity in Linux?

How do I throttle network activity, system-wide? Say, I'm running rsync on a large archive with a cron, or a torrent server, or both. It's important that these activities will be running, but they ...
1
vote
1answer
737 views

Running a custom script when StrongSwan connection is established

I have StrongSwan VPN server set up on a Debian host, and would like to run a custom script when a client connects to it. The only thing I have come up with is periodically checking the contents of ...
8
votes
1answer
579 views

TCP packet being retransmitted 7 times when sysctl tcp_retries1 is set to 3 - why?

Ubuntu 12.04 I am trying to better understand how many times TCP will attempt to retransmit a packet when it does not receive confirmation the destination received it. After reading the tcp man page ...
1
vote
1answer
1k views

What's the difference between eth0:1 and 2nd eth0?

In Ubuntu server, I configured eth0:1 like this in /etc/network/interfaces file # The primary network interface auto eth0 iface eth0 inet static address 192.168.1.111 netmask ...
0
votes
0answers
29 views

Do I need a firewall if the service doesn't listen on all interfaces? [duplicate]

Short version: I have a CentOS 6.5 with two NICs, one connected to the internet and one connected to the internal network. The services that shouldn't be accessible to the internet don't listen on ...
0
votes
3answers
82 views

benefits of iptables on VPS? [duplicate]

Say I have a well updated Linux VPS serving HTTP content on port 80 using apache. What would I gain by enabling IPtables? I can see no obscurity gains since the machine has a port open. Also, since ...
0
votes
2answers
264 views

Http Persistent Connection (keep-alive) and port numbers

Is a persistent http connection (keep-alive), always bound to a specific port, or can it use a range of ports?