Wednesday, December 31, 2008


DHCP Stands for the Dynamic Host Configuration protocol and it is used to assign the IP addresses to the network computers dynamically. It saves the lot of time and the administrative efforts of the network administrators by providing the TCP/IP configurations such as IP address, subnet mask, default gateway address, DNS, router, proxy server and the settings to the client computers.

With the DHCP, the process of connecting the new client computer with the server is very easy. Just imagine that if you are assigned a task of provide the IP addresses and other TCP/IP configurations to1000 client computers manually then how lengthy and tiring task it can be. DHCP sever assigns the IP addresses from its predefined fixed pool of the IP addresses.

In the DHCP pool, you can define the range, leased duration and map the IP addresses with the specific computers. The IP addresses allocation can be manual, automatic and dynamic. Sometimes in the computer networks, DHCP failure occur due to several reasons and in this situation the client computer will not be able to connect to the server and get the server resources. The problems may arise at the client end or the DHCP server end.

DHCP Client Troubleshooting
Many Client Computers are unable to get the IP Addressees from the DHCP Server

It can be due to the reason that the IP address of the DHCP server has been changed and the client computers are not able to connect to the DHCP server. Additionally the client computers are located behind the firewall or are connected to the DHCP server through the router. It is also possible that the multiple DHCP servers exist in the same LAN.

The solutions of these problems are to make sure that the DHCP server’s IP address fall in the same range of the IP addresses as the scope it is serving. For a DHCP server to provide the IP address to the remote subnets, the router should act as DHCP relay. Make sure that you are not configuring the multiple DHCP servers on the same LAN with the same scope of the IP addresses as it can cause the conflicts in the IP addresses.

The DHCP client does not have IP addresses configured

It can happen due to the reason that the client computer is unable to connect to the DHCP server and obtain the IP address from it or the DHCP server is unavailable. To resolve this issue, you need to make sure that the client computer has connectivity with the DHCP server and the network cable and network connections are accurate. Then try to ping the DHCP server and make sure that you are getting reply from the server.

DHCP client has automatically assigned IP address to itself

In the Windows 98, XP Professional and the Windows ME sometimes the client computers are unable to connect to the DHCP server so they assign the IP addresses automatically through the IP auto configuration.

DHCP Server Troubleshooting

Sometimes if the multiple client computers are experiencing problems in leasing the IP address from the DHCP server then the problem is most likely with the DHCP server itself. The common problems that can arise in the DHCP server are the following.

DHCP server has been stopped

You need to check the log files and the system event files for details about this problem. These log files will provide the detailed information, causes and the solution of this problem.

One of Two DHCP Server is not serving the client

If this happens and if the server is a domain member then you need to authorize the DHCP server in the Active directory.

DHCP Server’s data is corrupted.

The DHCP server’s data has been corrupted or missing and possibly it generates the JET database errors. You need to use the DHCP data recovery options to recover the lost data and correct any of the generate errors. You can also use the reconcile feature in the DHCP console to verify and reconcile any inconsistencies in the database.

If you specific issue is not mentioned above then you need to visit the Microsoft’s website and review the DHCP troubleshooting articles for more details.


Exam Number/Code: 640-802
Exam Name: CCNA

"CCNA 's Cisco Certified Network Associate", also known as 640-802 exam, is a Cisco certification.
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Sunday, December 14, 2008

Dell Wireless and Ubuntu Hardy Heron

I have a Dell Inspiron 1520 with the Dell Wireless 1390 WLAN Mini-Card, one that has given many Linux users big headaches.

After trying many different approaches suggested all over the web, and gathering clues in many Ubuntu forum posts, I finally worked out this solution:

First of all you must check if you have the correct card:

lspci -nn | grep 14e4

Result: 05:00.0 Network controller [0280]: Broadcom Corporation BCM94311MCG wlan mini-PCI [14e4:4311 (rev 01)]

Then proceed to the first step:

1. blacklist bcm43xx

echo blacklist bcm43xx | sudo tee -a /etc/modprobe.d/blacklist

2. install ndiswrapper and related files

sudo apt-get install ndiswrapper-common ndiswrapper-utils-1.9 ndisgtk

3. download

this is a ridiculous bit of bloat, but the most complete INF for 43xx devices

4. Unzip the drivers.

5. go into folder DRIVER_US inside the result of what you did above

6. use ndiswrapper to install bcmwl5.inf

System -> Administration -> Windows Wireless Drivers -> Install New Driver -> Select bcmwl5.inf from ~/R151517/DRIVER_US

7. Modify rc.local

gksudo gedit /etc/rc.local

Insert these lines ABOVE “exit 0″ line:

modprobe -r b44
modprobe -r ssb
modprobe -r ndiswrapper
modprobe ndiswrapper
modprobe ssb
modprobe b44

8. Restart or simply paste one by one the following lines:

$ sudo rmmod b44
$ sudo rmmod ssb
$ sudo rmmod ndiswrapper
$ sudo modprobe ndiswrapper
$ sudo modprobe ssb
$ sudo modprobe b44

You should see the WiFi led on and you are good to go.

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