How Network Address Translation Work (How NAT Work)

At the present time broadband access has become commonplace and are available in many places, access the internet has become very easy and simple to do. The Internet can be accessed from home, schools, cafes and mobile handsets, and it's getting easier by the presence of a broadband router and NAT (Network Address Translation) as one of the technologies that empower them.
In computer networking, network address translation (NAT) is the process of modifying the IP address information in the IP packet headers while in transit across a traffic routing device. That means this NAT using a user in a private network will "hidden" from the Internet it self. This have some benefits, ie: Security, IP address re-use, easy configuration on the client side.
To Understand how the NAT work I share a link "How NAT Works" that may can be used by people to learn and Understand it easily.

http://www.cisco.com/en/US/tech/tk648/tk361/technologies_tech_note09186a0080094831.shtml#flash

[ Tips: ] Reboot a remote Cisco router after an misconfiguration

Human error!!! ..... it is common, even in network administration. But if this happen on the remote router or switch that do not have person/human that can physically reboot the device then it is become....disaster!!!!

So what is the option? We can use a simple and tricky way to avoid this situation.
In Cisco router we can use command reload in minutes before you do the command input. So when everything become unaccessible, the router will reboot to startup-configuration .

In my case I use 5 minutes (may be different to other) :

Cisco# reload in 5

so when my router cannot be accessed, it will reboot in 5 minutes . After that I can access it again.

Then do the configurations. You must do it 5 minutes otherwise the router will be reboot.

But if the configuration is successfully done, do not forget to cancel it with:

Cisco# reload cancel


That's all !!

Using Network Share in Windows XP

Do you have to connect to different folder in remote Windows XP share folder with different rights? For example, I sometimes need to copy a file to share folder "NOC" and after that I need to copy another file to share folder "ITDEPT".

Both of them located in remote windows computer that has different login and password for each (since this NOC and ITDEPT has different members). FYI the setting of rights of those folder in the remote server will be not provided here, but it it must be have read and write rights both on those folders with different logins. For this kind situation we can use below step:

For example in remote windows share you login as user "noc" with its password and will be directed to folder NOC automatically. Use this command from command prompt:

net use m: \\remotefileserver\NOC /user:Accounts\NOC

or you can use windows explorer to browse to that remote folder in the network neighborhood.
Then you copy a file to that folder. File copied succesfully.
After that you can disconnect the connection:

net use m: /delete


then reconnect to the same server with user "itdept" and its password:

net use m: \\remotefileserver\ITDEPT /user:Accounts\ITDEPT

Try to copy a file to "ITDEPT" folder. Now you can copy a file to it !!!

Just Another IM client

Wanna try something new in Instant Messenger? I found this good site. Here you will see their comment on some alternative Instant Messenger (IM). I think this is good for ones who need to online at the same time in more thant one account in same IM services like more than one account in Yahoo Messenger.

"Tired of using the big corporate instant messengers, or just looking at what else is out there? Either way, you've come to the right place. Here is a list of some other instant messengers that are out there. Some are even compatible with the big corporate instant messengers, which means you can still talk to your friends on AIM or Msn instant messenger. Check out the Interoperability chart to find out what messengers they are compatible with."

Live CD

This is a very good news for those who want to learn linux without effort to install or any risk lost data when install the Linux. TOday there is a site where you can download a LIVE CD and burn it to a CD/DVD. After that you can directly have linux distro in your computer without having to install the Linux to the harddisk.

Please find the site here !

Erase many files in 1 directory in UNIX/Linux

Almost 2 months since my last posting. I have many jobs to do specially non technical made me have no time to continue spread the knowledge to others. Since today I will try to make a posting at least once a week to keep the readers update about this site.

This time I will write about "Erase many files in 1 directory in UNIX/Linux" since I got one case when the logrotate of one of my server using BSD had corrupted and I had no time to fix the logrotate package. So I made a little script and crontab-ed it like once a day in the period of minimum traffic. I use it to clean the quarantince files in qmail. Here the script
(clean-quarantine.sh):

ns1# cd /var/spool/qmailscan/quarantine/new/
ns1# ls | xargs rm

This script helped me to keep the harddrive not full when there is no logrotate process running.

Setting NTP client in Huawei Datacomm Equipment (Router, Switch, Firewall)

At past post I showed how to setting syslog in Huawei equipments. Now I will show how to make a Huawei equipments synch their time to a centralized server using NTP protocol.
Setting the IP adddres of the NTP server (if you are using NTP server with higher stratum):

ntp-service unicast-server 10.0.10.4

or if you want to sync to other peer (with same stratum):

ntp-service unicast-peer 10.0.11.7

to make router only listen ntp from verified network (increase security), add this line:

source-interface Ethernet 1/0/6

then check the ntp synchronization using command:

display ntp-service status
display ntp-service sessions