Domain Name system (DNS ) is using to assign names for a particular IP address. In Internet every communication is based on IP address. It is difficult to remember the 32 bit IP address and DNS server is resolving that issue by assigning a unique name for particular IP address. So if one user type one domain name on the browser the communication is like this.

Web browser——-> DNS Server

DNS server ———> Web server

The name to IP address conversion is also done in DNS server and it is very important that every computer should know the address of DNS server. So we need to set DNS address on every computer for the proper Internet communication.

How to set DNS(Domain Name System) from DOS prompt using single command

We can set DNS address for a computer from the command promptby a single command. The command to set DNS for a computer is:

netsh interface ip set dns “Local Area Connection” static 192.168.1.50

Where the interface is Local Area Connection

The IP address is 192.168.1.50

After global DNS and Open DNS we have one more choice in setting a reliable DNS services. Google introduce a new set of public DNS address called Google Public DNS which offers a high speed more secure DNS services. The addresses are:

8.8.8.8 and

8.8.4.4

[ DNS is used to covert domain name to corresponding IP address and vice versa. ]

Google has launched telephone support for the issues related to Google Public DNS service. The telephone numbers are:

* 877-590-4367 { For US customers }

* 770-200-1201 { Outside US }

To set Google Public DNS in your computer from command prompt click on the link below.

Setup DNS address on your computer from Command Prompt

To know more about Google Public DNS service please click on the link provided below.

http://code.google.com/speed/public-dns/docs/using.html

We have a server with dedicated IP address in my company’s headquarter. There’re a couple of branches at other locations. We need to setup servers in each branch and allow accessing to those servers through dedicated subdomain name. But we do not have static IP for those branches, so it’s not possible to bind any IP in our DNS server at headquarter.

If you have the same need as we are, here’s what we did to resolve the problem.

Basically we need to setup DNS Update service at branch site to perform remote DNS update to headquarter to update IP of subdomains used by branch site periodically, so headquarter’s DNS will always know the correct IP of each branch server.

For example, our main domain is infolexllc.com, and we need to setup a branch server at New York which will be called ny.infolexllc.com, here’s what we do at servers at both ends (both CentOS 5.X):

At branch site(where only dynamic IP is available):
1. Install NS Update:

yum install bind-utils

2. Create folder to hold related files and scripts:

mkdir /root/nsupdate
cd /root/nsupdate

3. create key files for NS update

dnssec-keygen -a HMAC-MD5 -b 512 -n USER ny.infolexllc.com
Kny.infolexllc.com.+157+47223

4. You should have two new files created under the current folder:

Kny.infolexllc.com.+157+47223.key  Kny.infolexllc.com.+157+47223.private
5. create a new shell file: donsupdate.sh:


#!/bin/sh

cd /root/nsupdate

HOST=ny.infolexllc.com.

#Get branch site's IP

IPADDR=`links -source http://whatismyipaddress.com/ |grep -o 'Your IP address is [0-9.]*'|cut -d : -f 2|awk '{print $5}'`
NSUFILE=./nsupdate
FLAGFILE=./nsupdate.flag

if [ "" = "$IPADDR" ]; then
 echo Error detecting current  I will exit.
 exit 0;
else
 echo Detected IP address is:$IPADDR
fi

FLAG=`date +%H`:$IPADDR

if [ -a $FLAGFILE ]; then
 FLAG_IN_FILE=`cat $FLAGFILE`
fi

if [ "$FLAG" == "$FLAG_IN_FILE" ]; then
 #Flag is same, skip it

 echo IP is not changed in the passwd hour, so I will skip
 exit 0;
else
 echo IP has been changed or one hour has been passed, save the flag and do update...
 echo $FLAG > $FLAGFILE
fi

#change infolexllc.com to your head quarter site's domain name

HQ_DOMAIN_NAME=infolexllc.com
echo "server $HQ_DOMAIN_NAME" > $NSUFILE
echo "zone infolexllc.com" >> $NSUFILE
echo "update delete $HOST A" >> $NSUFILE
echo "update add $HOST 84600 A $IPADDR" >> $NSUFILE
echo "show" >> $NSUFILE
echo "send" >> $NSUFILE
nsupdate -k ./Kny.infolexllc.com.+157+47223.private -d $NSUFILE


Make sure you change value of the script based-on your own environment.
6. Open the newly generated key file Kny.infolexllc.com.+157+47223.key
ny.infolexllc.com. IN KEY 0 3 157 QLwMCWdqUJ/ZOsOsdF4Dj/mYD2XwmqSrPL540JE3dwG7FXZwrJulOp16 Y0SySnfOo7+5s1mhZhUiAHxVOSoXnQ==
Remember the key string started from QlwMC.. all the way to the ending ==



On headquarter server:

7. Modify named comnfiguration to allow remote DNS update from ny.infolexllc.com
Open /etc/named.conf

Find zone "infolexllc.com" {

Insert the following section in the configuration file before the zone:

key ny.infolexllc.com.{

algorithm hmac-md5;

secret "QLwMCWdqUJ/ZOsOsdF4Dj/mYD2XwmqSrPL540JE3dwG7FXZwrJulOp16 Y0SySnfOo7+5s1mhZhUiAHxVOSoXnQ==";

};
Insert the following lines at end of the infolexllc.com zone:

allow-update {

key  ny.infolexllc.com. ;

};
Restart DNS server:
/etc/init.d/named restart
Now the headquarter DNS server should allow remote DNS update from ny.infolexllc.com
On branch server:

8. Test DNS update script:

run
donsupdate.sh
You should see messages like below:
Detected IP address is:123.123.123.123
IP has been changed or one hour has been passed, save the flag and do update...
Creating key...
before getaddrinfo()
Outgoing update query:
;; ->>HEADER<<- opcode: UPDATE, status: NOERROR, id:      0
;; flags: ; ZONE: 0, PREREQ: 0, UPDATE: 0, ADDITIONAL: 0
;; UPDATE SECTION:
ny.infolexllc.com. 0 ANY A
ny.infolexllc.com. 84600 IN A 123.123.123.123

Reply from update query:
;; ->>HEADER<<- opcode: UPDATE, status: NOERROR, id:  25321
;; flags: qr ; ZONE: 0, PREREQ: 0, UPDATE: 0, ADDITIONAL: 1
;; TSIG PSEUDOSECTION:
ny.infolexllc.com. 0 ANY TSIG hmac-md5.sig-alg.reg.int. 123123123123 300 16 ABCabcABCabc123+12aBcde== 25321 NOERROR 0

The status: NOERROR indicates a succeful update.

If you see any other error in status, go check /var/log/messages on head quarter server to find clue.
9. Test the new domain:
ping ny.infolexllc.com
You should see the new domain can be resolved to the dynamic IP currently assigned to branch server.
10.

Once update script is working, you can create a cron job on branch

server to run the script every 10 minutes. The script itself will check

if IP has not been changed in the past hour, it will skip remote update.
I've

done this for our branch servers several times. It works very well so

far. I hope this set up can help resolving your problem. Feel free to

let me know f you have any feedback or question.
Cheers!

ny.infolexllc.com. IN KEY 0 3 157 QLwMCWdqUJ/ZOsOsdF4Dj/mYD2XwmqSrPL540JE3dwG7FXZwrJulOp16 Y0SySnfOo7+5s1mhZhUiAHxVOSoXnQ==

/etc/init.d/named restart

donsupdate.sh

Detected IP address is:123.123.123.123
IP has been changed or one hour has been passed, save the flag and do update...
Creating key...
before getaddrinfo()
Outgoing update query:
;; ->>HEADER<<- opcode: UPDATE, status: NOERROR, id:      0
;; flags: ; ZONE: 0, PREREQ: 0, UPDATE: 0, ADDITIONAL: 0
;; UPDATE SECTION:
ny.infolexllc.com. 0 ANY A
ny.infolexllc.com. 84600 IN A 123.123.123.123

Reply from update query:
;; ->>HEADER<<- opcode: UPDATE, status: NOERROR, id:  25321
;; flags: qr ; ZONE: 0, PREREQ: 0, UPDATE: 0, ADDITIONAL: 1
;; TSIG PSEUDOSECTION:
ny.infolexllc.com. 0 ANY TSIG hmac-md5.sig-alg.reg.int. 123123123123 300 16 ABCabcABCabc123+12aBcde== 25321 NOERROR 0

ping ny.infolexllc.com

‘m using a Cisco Linksys WAG320N Router to connect my OS X UNIX and Linux systems to the Web. How do I reboot my Linksys WAG series router / gateway (modem) from UNIX / Linux / OS X bash command prompt or using a shell script?

The Cisco linksys series modem removed reboot option from its web interface but you can reboot the router using the following url format:

http://your-router-ip/setup.cgi?todo=reboot

http://192.168.1.1/setup.cgi?todo=reboot

Sample outputs:

Fig.01: Rebooting Cisco Linksys Router / Gateway

The web interface hack works with any web browser regardless of the operating system.

Command Line Options

curl is a command line tool for transferring data with URL syntax, supporting various protocosl such as FTP, FTPS, HTTP, HTTPS, SCP, SFTP, TFTP, TELNET, DICT, LDAP, LDAPS, FILE, IMAP, SMTP, POP3, RTMP and RTSP. curl supports SSL certificates, HTTP POST, HTTP PUT, FTP uploading, HTTP form based upload, proxies, cookies, user+password authentication (Basic, Digest, NTLM, Negotiate, kerberos), file transfer resume, proxy tunneling and much more. The same tool can be used to reboot your router as follows:

curl -u 'Router-username:password' 'http://192.168.1.1/setup.cgi?todo=reboot'
curl -u 'admin:Your-Password-Here' 'http://192.168.1.1/setup.cgi?todo=reboot'

Further readings:

man curl

Changing Hostname Temporarly

Example: hostname newhostname.com

Changing Hostname Permanently

Edit the file /etc/rc.conf and change the value in it, Save and exit

Changing/Setting main ip

Edit the file /etc/rc.conf and change the value of ifconfig_ed0 (The interface name can be different)

Example rc.conf file:

### Basic network options: ###
hostname=”myname.my.domain” # Set this!

network_interfaces=”lo0″ # List of network interfaces (lo0 is loopback).
You will need to amend this line to tell FreeBSD that you want to add
another device, namely the ‘ed0′ device. Change this line to read:
network_interfaces=”lo0 rl0″ # List of network interfaces (lo0 is loopback).
Beneath the line that specifies which interfaces should be activated
are the lines that specify the actual settings for each interface. In
the default /etc/rc.conf file is a single line that says:

ifconfig_lo0=”inet 127.0.0.1″ # default loopback device configuration.
#You will need to add another line after that to specify the settings for your ‘ed0′ device.

#For our sample configuration we will insert a line immediately after the loopback device definition that says:

ifconfig_rl0=”inet 2.1.12.5 netmask 255.255.255.0″

Adding more IPs

Add aliases in /etc/rc.conf
#More ips will be aliases
ifconfig_rl0_alias0=”inet 2.1.12.6 netmask 255.255.255.0″
ifconfig_rl0_alias1=”inet 2.1.12.7 netmask 255.255.255.0″

OR Execute below commands
ifconfig rl0 inet 2.1.12.6 netmask 255.255.255.0 alias up
ifconfig rl0 inet 2.1.12.7 netmask 255.255.255.0 alias up

Updating FreeBSD and installing ports

#Some softwares use cvsup
cd /usr/ports/net/cvsup-without-gui
make install

#Installing portsnap
pkg_add -r portsnap
mkdir /usr/ports
portsnap fetch
portsnap extract
portsnap update

#Installing apache- It will install perl/python and other dependencies etc automatically
cd /usr/ports/www/apache22
make
make install

#Installing mysql5
cd /usr/ports/databases/mysql50-client
make
make install

cd /usr/ports/databases/mysql50-server
make
make install

#Start scripts are below to start stop them manually

/usr/local/etc/rc.d/apache22.sh
/usr/local/etc/rc.d/mysql-server.sh

# Add the following line to /etc/rc.conf to enable mysql:
# mysql_enable=YES: Set to “NO” by default.
# Set it to “YES” to enable MySQL.
# mysql_limits (bool): Set to “NO” by default.
# Set it to yes to run `limits -e -U mysql`
# just before mysql starts.
# mysql_dbdir (str): Default to “/var/db/mysql”
# Base database directory.
# mysql_args (str): Custom additional arguments to be passed
# to mysqld_safe (default empty).

Firewall Setup

#Load kernel module
kldload ipl

#executing firewall script manually

ipf -Fa -v -f /etc/ipf.rules.script

#Exampl script
#Setup the default allow all rule
pass out from any to any
pass in from any to any

#Allow some ip and your isp ip
pass in quick on rl0 from 4.35.9.0 to 4.35.9.255

#block tcp and icmp traffic for public
block in on rl0 proto tcp from any to any
block in on rl0 proto icmp from any to any

#Allow these for public
pass in on rl0 proto tcp from any to any port = www
pass in on rl0 proto tcp from any to any port = 443
pass in on rl0 proto tcp from any to any port = 21

Changing Hostname Temporarly

Example: hostname newhostname.com

Changing Hostname Permanently

Edit the file /etc/sysconfig/network and change the value of HOSTNAME in it, Save and exit

To avoid dns errors edit the file /etc/hosts and create a line as below
192.168.1.50 newhostname alias
Change ip with your server ip and newhostname and alias with anything you have setup

Changing/Setting main ip

Edit the file /etc/sysconfig/network-scripts/ifcfg-eth0 and change the value of IPADDR, NETMASK , NETWORK and BROADCAST
Example ifcfg-eth0 file:

DEVICE=eth0
BOOTPROTO=none
BROADCAST=192.168.1.255
IPADDR=192.168.1.50
NETMASK=255.255.255.0
NETWORK=192.168.1.0
ONBOOT=yes
USERCTL=no
PEERDNS=no
TYPE=Ethernet

Description: Dont forget to restart network after the change with below command
service network restart
Connect again using new ip if all is well.

Adding more IPs

# Copy the config file to create an alias ip
cp /etc/sysconfig/network-scripts/ifcfg-eth0 /etc/sysconfig/network-scripts/ifcfg-eth0:1

#Now edit the new file /etc/sysconfig/network-scripts/ifcfg-eth0:1
and change “DEVICE=eth0″ to “DEVICE=eth0:1″ and change ip to the new ip
you want to assign. Save and exit. Then use tbe below command to bring
it live.
ifup eth0:1

Adding a range of IPs

# Remove ifcfg-eth files from /etc/sysconfig/network-scripts/
#Create a file /etc/sysconfig/network-scripts/ifcfg-eth0-range0 if this
doesn’t exist, or just add to it if you already have it, the following
lines:

IPADDR_START=192.168.0.100IPADDR_END=192.168.0.200CLONENUM_START=0

where: IPADDR_START is the first IP and IPADDR_END is the last IP
in the range. CLONENUM_START is the number that will be assigned to the
first IP alias interface (eth0:0 in this example).

If you need to add more ranges of IPs then just use a different file
for ex. ifcfg-eth0-range1, for each one of the ranges. You need to be
careful and use the proper CLONENUM_START to not overwrite other
aliases. Once you have configured the range/s of IPs you just need to
restart the network service in order to activate it:

service network restart

Changing Hostname Temporarly

Example: hostname newhostname.com

Changing Hostname Permanently

Edit the file /etc/HOSTNAME and change the value in it, Save and exit

To avoid dns errors edit the file /etc/hosts and create a line as below
192.168.1.50 newhostname alias
Change ip with your server ip and newhostname and alias with anything you have setup

Changing/Setting main ip

Edit the file /etc/sysconfig/network/ifcfg-eth0 and change the value of IPADDR, NETMASK , NETWORK and BROADCAST
Example ifcfg-eth0 file:

DEVICE=eth0
BOOTPROTO=none
BROADCAST=192.168.1.255
IPADDR=192.168.1.50
NETMASK=255.255.255.0
NETWORK=192.168.1.0
ONBOOT=yes
USERCTL=no
PEERDNS=no
TYPE=Ethernet

Description: Dont forget to restart network after the change with below command
/sbin/rcnetwork restart
Connect again using new ip if all is well.

Adding more IPs

# Copy the config file to create an alias ip
cp /etc/sysconfig/network/ifcfg-eth0 /etc/sysconfig/network/ifcfg-eth0:1

#Now edit the new file /etc/sysconfig/network/ifcfg-eth0:1 and
change “DEVICE=eth0″ to “DEVICE=eth0:1″ and change ip to the new ip you
want to assign. Save and exit. Then use tbe below command to bring it
live.
/sbin/rcnetwork restart

Changing Hostname Temporarly

Example: hostname newhostname.com

Changing Hostname Permanently

Edit the file /etc/conf.d/hostname and change the value in it, Save and exit

To avoid dns errors edit the file /etc/hosts and create a line as below
192.168.1.50 newhostname alias
Change ip with your server ip and newhostname and alias with anything you have setup

Changing/Setting main ip

Edit the file /etc/conf.d/net and change the IP and Gateway in it.
Example net file:
config_eth0=(
25.35.25.12/24
25.35.25.13/24
)
routes_eth0=( “default gw 25.35.25.1″ )

Description: Dont forget to restart network after the change with below command
/etc/rc.d/net.eth0 restart
Connect again using new ip if all is well.

Adding more IPs

Simply add more ips in /etc/conf.d/net

config_eth0=(
25.35.25.12/24
25.35.25.13/24
25.35.25.14/24
25.35.25.15/24
25.35.25.16/24
25.35.25.17/24
)
routes_eth0=( “default gw 25.35.25.1″ )

Changing Hostname Temporarly

Example: hostname newhostname.com

Changing Hostname Permanently

Edit the file /etc/HOSTNAME and change the value in it, Save and exit

To avoid dns errors edit the file /etc/hosts and create a line as below
192.168.1.50 newhostname alias
Change ip with your server ip and newhostname and alias with anything you have setup

Changing/Setting main ip

Edit the file /etc/rc.d/rc.inet1.conf and change the value of IPADDR and NETMASK

Example rc.inet1.conf file:

# Config information for eth0:
IPADDR[0]=”33.74.27.5″
NETMASK[0]=”255.255.255.0″
USE_DHCP[0]=”"
DHCP_HOSTNAME[0]=”"

# Config information for eth1:
IPADDR[1]=”"
NETMASK[1]=”"
USE_DHCP[1]=”"
DHCP_HOSTNAME[1]=”"

# Default gateway IP address:
GATEWAY=”33.74.27.1″

Adding more IPs

Execute below commands and Add them in /etc/rc.d/rc.local
/sbin/ifconfig eth0:1 33.74.27.5
/sbin/ifconfig eth0:2 33.74.27.6
/sbin/ifconfig eth0:3 33.74.27.7

Changing Hostname Temporarly

Example: hostname newhostname.com

Changing Hostname Permanently

Edit the file /etc/sysconfig/network and change the value of HOSTNAME in it, Save and exit

To avoid dns errors edit the file /etc/hosts and create a line as below
192.168.1.50 newhostname alias
Change ip with your server ip and newhostname and alias with anything you have setup

Changing/Setting main ip

Edit the file /etc/sysconfig/network-scripts/ifcfg-eth0 and change the value of IPADDR, NETMASK , NETWORK and BROADCAST
Example ifcfg-eth0 file:

DEVICE=eth0
BOOTPROTO=none
BROADCAST=192.168.1.255
IPADDR=192.168.1.50
NETMASK=255.255.255.0
NETWORK=192.168.1.0
ONBOOT=yes
USERCTL=no
PEERDNS=no
TYPE=Ethernet

Description: Dont forget to restart network after the change with below command
service network restart
Connect again using new ip if all is well.

Adding more IPs

# Copy the config file to create an alias ip
cp /etc/sysconfig/network-scripts/ifcfg-eth0 /etc/sysconfig/network-scripts/ifcfg-eth0:1

#Now edit the new file /etc/sysconfig/network-scripts/ifcfg-eth0:1
and change “DEVICE=eth0″ to “DEVICE=eth0:1″ and change ip to the new ip
you want to assign. Save and exit. Then use tbe below command to bring
it live.
ifup eth0:1

Adding a range of IPs

# Remove ifcfg-eth files from /etc/sysconfig/network-scripts/
#Create a file /etc/sysconfig/network-scripts/ifcfg-eth0-range0 if this
doesn’t exist, or just add to it if you already have it, the following
lines:

IPADDR_START=192.168.0.100IPADDR_END=192.168.0.200CLONENUM_START=0

where: IPADDR_START is the first IP and IPADDR_END is the last IP
in the range. CLONENUM_START is the number that will be assigned to the
first IP alias interface (eth0:0 in this example).

If you need to add more ranges of IPs then just use a different file
for ex. ifcfg-eth0-range1, for each one of the ranges. You need to be
careful and use the proper CLONENUM_START to not overwrite other
aliases. Once you have configured the range/s of IPs you just need to
restart the network service in order to activate it:

service network restart