the IP protocol and IP addresses

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6
votes
2answers
5k views

How to build a gateway from my Linux OS

I want to configure my Linux so that it will be used as a network router (gateway). Can anybody give me some hints on this? (links are welcome!)
2
votes
1answer
6k views

Static route in Centos 6

Here is my route -n output: Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 192.168.122.0 0.0.0.0 255.255.255.0 U 0 0 ...
4
votes
1answer
272 views

Inserting a nat solution into a network while it's not the gateway

I have tried this a few different ways. Currently trying with pf on freebsd 8.2 I am trying to insert a nat solution into an existing network that will redirect traffic from an outside ip address to ...
2
votes
1answer
435 views

Should OpenVPN point to point tunnels be on different ports?

The OpenVPN cookbook shows an example for site-to-site VPN (3 sites). They configured each tunnel on a unique port: site A to site B: 1194 site A to site C: 1195 site B to site C: 1196 The author ...
3
votes
2answers
1k views

IP rule for IPv6

When I try to add an IP rule for IPv6 on my Linux system, it errors out: $ ip -6 rule add fwmark 0xfab lookup 0xf RTNETLINK answers: Address family not supported by protocol I checked out the IP ...
2
votes
5answers
4k views

script to scan ip range and return results in a certain format

This script scans IP's and returns a status of Up or Down. How can I alter it so it doesn't scan everything twice? As it sits it scans everything and returns the "Up" addresses only and then scans all ...
2
votes
1answer
3k views

Testing if a port was forwarded correctly in Ubuntu

I have a Ubuntu box connected to a wifi router. This wifi router is connected to a d-link adsl modem/router. I am preparing this Ubuntu box to run a server that will use some special ports in UDP and ...
48
votes
2answers
6k views

How does SSH connection survive a network restart?

From a Linux SSH shell, type /etc/init.d/network restart to restart the network service. I expect my SSH connection to die since the network service goes down. But it doesn't. Very cool. But how does ...
2
votes
1answer
504 views

ICMP destination unreachable

I am working on an Arch Linux machine with an ethernet interface eth1. I have created the interface eth1:0 using ifconfig and given it a dummy hardware address (00:01:02:03:04:05). When I send a UDP ...
7
votes
3answers
6k views

What's the last number in this ip address?

An IP address like this 223.248.0.0/24 or 223.248.0.0/16 What's the last number mean in the IP address (24 or 16 in the above example)? Is there a simple way to understand how to set the number ...
4
votes
2answers
406 views

How can I use one network port for VPN and the other for everything else?

My Linux machine has two network ports with two IP addresses. I want to use one port for my VPN and accounting, and the other port for other usages. How can I tell Linux not to allow any requests from ...
3
votes
1answer
454 views

What is the kernel doing when I bring a TUN/TAP interface up

I'm playing around with the TUN/TAP device on Linux. I've created a simple program that creates a TAP interface and prints anything that is sent through it. When I bring the interface up with ip link ...
6
votes
3answers
44k views

How can I know if IP Multicast is enabled

I have scripts that run IP multicast tests; however, my scripts are failing on a particular linux machine. I know that I can look at CONFIG_IP_MULTICAST in the kernel configuration file to determine ...
3
votes
1answer
417 views

Labeling/Aliasing multiple network addresses

If my machine is connected to several networks and configured with multiple addresses (ipv4), is it wise to configure and use labels to identify them ? By labels I mean the iproute2 ip command's ...
2
votes
1answer
3k views

iptrace for linux: how can I trace full packet contents?

I normally use iptrace on our AIX servers to get packet traces but have recently found out that this doesn't work for other 'nix systems - namely Centos. Does anyone know what the analog would be? ...
1
vote
2answers
360 views

Is it possible assigning an separate LAN IP to service/daemon?

I'm using pfsense for prioritizing traffic around LAN. It works well for specified port, IP, network, but I'm having a problem with torrent (transmission bittorrent) outbound connections. The outbound ...
3
votes
1answer
226 views

Detecting multihomed machine

Is there a way to reliably detect whether or not a machine is multi-homed? I'd like to be able to write a script that will return a true or false regarding that information.
2
votes
5answers
7k views

How to get netmask from bash?

I want to get my netmask on Linux. It is outputted with ifconfig but I want to extract the string.
4
votes
2answers
840 views

How to configure Linux to use DHCP or static IP depending on presence/absence of DHCP server?

I would like to configure a network interface to make use of DHCP if a DHCP server is present on the network during boot, but otherwise default to some default static IP address.
2
votes
2answers
295 views

How to deny rdesktop access to others?

Someone keeps trying to connect to my Ubuntu machine through remote desktop. Is there any way I can determine who it is, and permanently block access to my machine?
9
votes
2answers
19k views

show gateway IP address when performing ifconfig command

Currently, when using the ifconfig command, the following IP addresses are shown: own IP, broadcast and mask. Is there a way to show the related gateway IP address as well (on the same screen with ...
70
votes
19answers
58k views

How can I get my external IP address in bash?

I need to find my external IP address from a bash script. At the moment I use this function: myip () { lwp-request -o text checkip.dyndns.org | awk '{ print $NF }' } But it depends on ...
4
votes
4answers
7k views

Make some virtual MAC address

I want to make some virtual MAC addresses for my network adapter or wireless adapter, so I can connect to network with more than one IP address from one computer or laptop. How can I do it? (I know ...
-1
votes
1answer
496 views

How to “grep -v” private/broadcast IPv4 addresses?

time nmap -n -iR 0 -sL | cut -d " " -f 5 | egrep -v "^10.*|^172.[16\-32].*|^192.168.*|^[224\-255].*" > RANDOM-IPS.txt so the important part is: egrep -v ...
2
votes
1answer
774 views

static ip to a freebsd server

I have Comcast cable <====> modem <===> router <===> freebsd server My freebsd server is connected to wireless router via a network cable. What I want to do is, to have a static ...
5
votes
3answers
4k views

How to filter IPv4 and IPv6 addresses?

echo "1.1.1.1" | awk '/[0-9]*\.[0-9]*\.[0-9]*\.[0-9]*/ {print $1}' How can I filter IPv4 addresses in a script, and how can I filter IPv6 addresses. I mean more precisely then this so the oneliner ...
2
votes
1answer
660 views

Is it possible to use Internet Connection Sharing with DHCP?

I know it is possible to share an internet connection with another pc using ip-forwarding and masquerade. Is it possible to set up the sharing computer as a DHCP server, so the settings (ip, gateway, ...
4
votes
1answer
2k views

How to set a static IP in Ubuntu

How do I set my computer to have a static IP in Ubuntu 11.04? The only two lines in /etc/network/interfaces are: auto lo iface lo inet loopback I think usually when people do this they have a wired ...
4
votes
2answers
2k views

What tools do I need to intercept and change an incoming packet on a WP2-Personal wifi hub

Which tools should I research into to intercept a plain text packet, edit it and then continue it on it's way. I am using Ubuntu 11.04 and Backtrack 5; my wifi is WPA2-person encrypted. I need to edit ...
4
votes
1answer
2k views

Two IP addresses assigned to the same machine?

I seem to be using two IP addresses on my PC. I use DHCP to get an IP address and then I statically set an IP address and activate it. ifconfig says that I am using the address given by DHCP but I am ...
0
votes
2answers
2k views

How to generate random IP addresses

$ nmap -n -iR 0 -sL > RANDOM-IPS-TMP.txt $ grep -o "[0-9]*\.[0-9]*\.[0-9]*\.[0-9]*" RANDOM-IPS-TMP.txt | egrep -v "10.*|172.[16-32].*|192.168.*|[224-255].*" > RANDOM-IPS.txt egrep: Invalid ...
4
votes
1answer
1k views

Running vim on a remote Linux machine “freezes” OS X SSH connection

(cross-posted this from SuperUser as the question seems more relevant to this audience) I am attempting to SSH to a Linux (Fedora 14) machine and then open up vim to edit a file, however on my new ...
0
votes
2answers
929 views

Understanding tcpdump output on a linux router

My router has an atm0 interface and a VLAN (atm0.1) interface, atm0.1 has the WAN IP address. When using tcpdump -i atm0, the packets captured are only outgoing packet (LAN to WAN). 05:34:19.504895 ...
10
votes
1answer
14k views

What is kernel ip forwarding?

I have seen on many blogs, using this command to enable IP forwarding while using many network security/sniffing tools on linux echo 1 > /proc/sys/net/ipv4/ip_forward Can anyone explain me in ...
1
vote
0answers
564 views

Wrong route taken on a network with two gateways [closed]

In the following output, why does vpn1 route pings to 10.100.0.1 instead of 10.100.0.112? 10.100.0.1 is a network gateway with no NAT; 10.100.0.112 is a dual-homed host with NAT enabled. root@vpn1:~# ...
2
votes
1answer
406 views

Can't access HTTP contents, but HTTPS and SSH are fine

I'm having a weired issue wih my Fedora 14 recently. Many details involed. Let's start from this: I've been using Fedora 14 for months, and recent few days, offten I can't access Internet for hours. ...
1
vote
3answers
716 views

How to set Internet Protocol properties using terminal?

When I set up a Virtual Machine with windows (using VMPlayer), I set the Network Connection properties from the VM settings from NAT to bridged. Then I proceed to set the following IP Properties in ...
2
votes
3answers
440 views

Port monitoring on GNU/Linux based NAT router

I am using a Ubuntu machine as a NAT router. How can I find out the following: the ports on which the LAN machines are listening or communicating (both tcp and udp); which local machines have ...
3
votes
3answers
2k views

Accessing a linux machine with a name (not ip address)

When I access a linux machine with sshfs, I take the following steps. Get the ip address of the linux (the ip address is dynamically allocated to linux) Run sshfs id@ip_address:/HOME_DIRECTORY Can ...
1
vote
3answers
1k views

Connect my laptop through desktop to internet

I'm currently at work and our wifi is down. I usually connect my desktop to the internet through eth0 and my laptop connects through wifi. I have an extra port on the back of the desktop (eth1) and ...
4
votes
3answers
3k views

Send duplicate packets over two Internet connections

I need to duplicate an RTP stream over two different (non-reliable) Internet connections. On the receiver side, I will probably run a custom program that will use a buffer and rebuild the stream ...
3
votes
4answers
2k views

Sniffing packets through router

I would like to create a system like this. The user would connect through a wifi network which would reroute all http requests and responses through the network card on a computer thus allowing that ...
18
votes
7answers
17k views

How to get my own IP address and save it to a variable in a shell script?

How can I get my own IP address and save it to a variable in a shell script?
1
vote
2answers
701 views

squid (reverse proxy) configuration

I would like to configure squid in such way, so that only specific (public) ip (reverse proxy), could connect to the server, but I don't know how... can someone tell me how to do this?
6
votes
3answers
397 views

SpamAssassin Under Linux VPS

I am getting bald with this guys: On a Linux VPS (CentOS), I have setup a mail server (Exim+Dovecot+Clamav+SpamAssassin) but scanning mail for spam using SpamAssassin is proving to be a challenge. I ...
5
votes
2answers
3k views

Can't ping broadcast

We're running four computers connected to a hub (yes a hub not a switch) on Fedora 13. They were installed using images from a colleague that has recently left us to go back to school, they may have ...
6
votes
1answer
3k views

avoid IPv6 link local address on interface

I have a setup with virtual Xen hosts connected to a set of VLAN-s. On Dom0, I have set up a bridge for each of my VLAN-s to connect DomU-s to. Bridges are set up in /etc/network/interfaces like ...
16
votes
2answers
3k views

IP to Country console command

Is there a console command that takes an IP address as an input and shows its geographical information like city, country, ISP, etc.?
8
votes
2answers
1k views

Measuring internet connection quality

I'm having WLAN trouble on my dualbooting win/linux laptop - the connection on linux side has occasional trouble, and seems somewhat slow and chunky. I would try to fix this issue by fiddling with all ...
2
votes
1answer
416 views

Redhat Enterprise Linux 4.7 - Ping problem

When I try to ping some of the IP addresses I get "connect: No buffer space is available" error. Also when I check /var/log/messages, there are some errors like as following printk: 99 messages ...