Monday, May 02, 2005

ATHow to Crimp Straight and Cross over cable

Crimping HOWTO

Gives clear details on how to crimp straight and cross over CAT5 cable

Mission BunNet

Today is 4th day of my trip at our MP project site, entire project site computer network was down, minor problem was their since one week, but last 2 days, nothing was working.
No email
No Internet
No Network
No Printer
at this site phone hardly works, even that was dead :-(

I don't have to say that the project leader was frustated at a very crucial stage of the the project.

had to rush to the site to fixup the problem, in my 3 years of IT experience, this was my first such trip, on a critical mission when the entier network was down, I had to bring it up quickly and go back to main office, was not sure how much time it would take to find out the root cause of the problem, which has brought down entier network and stopped all type of communication to the outside world.

For internet, this site uses a VSAT connection provided by HECL, India

Reached project site on 29th April 2005, Friday evening, had a look at the network, only one laptop was connected directly to the VSAT unit and all were using this to access their emails.
Files were trasfered from one system to other using a Flash drive.
Recently the office was expanded one more room was added, to which few CAT5 cables were layed out from the switch to the workstation tables.

It was late evening when I reached when I reached the camp, went to bed, planned the action to take up the next day, first place to be tested was the new cables setup in the office, VSAT status, a call was logged with HECL who had sent a field engineer for testing, the engineer was on site when I reached. There was miss allignment of the VSAT anteena, which was corrected, VSAT was working fine, tested the internet speed, it was at a decent speed, latency to google.com was around 1500ms (yes this is the latency what we get at this site), at best we get 1000ms latency at this site when ping to google.com

Removed all the CAT5 cables from the office, tested by connecting one end to laptop and other end to switch, except one cable, none were working, it was crimped in the wrong order, luckily I had brought my crimping tool and RJ45 connector, reason I said luckily because if I had not got the connectors I had to wait for one more day to get them, the site is in such remote location, for which we do not have time, recrimpled all the cables and fixed the issue.

CAT5 crimping colour code sequence:
white/orange, orange, white/green, blue, white/blue, green, white/brown, brown

Still I was not able to understand is
In star topology if one cable is not working, that should not bring down the entire network, this happens on only bus or ring topology.

Other reason for which the network was down was, the network was a peer to peer network, which can handle only 10 concurrent connections, last week we had about 12 computers on the network which might be the reason for the network going down.

As I said we have a peer to peer network and we do not provide static IP address for our computers, we didn't have a DHCP server in the network, we used the VSAT DW6000 unit which had option of enabling DHCP services so that network computer can get IP address from that unit, we had a range of 15 IP address which we could use, if the DW6000 unit is disconnected from the network, then computers on the network will continue to work until its restarted, once restarted, it tries to get an IP address from DHCP server, if not found then windows XP gives and AIPA (Autoconfig IP Addressing) in a different subnet mask then the VSAT IP address range, this conflicts and the computers can't talk to each other.
Connection between the computers can be re-established only if all the computers get an AIPA, which can be done, by restarting the computers.

This works for Windows XP computers, but for network printers, it can't get an automatic IP address, hence network printers goes down. I could have given an static IP address, but the DHCP service from the DW6000 had a limitation, we couldn't reserve a range of IP address, without a range, would create an IP address conflict, hence left to get dynamic IP address for network printers.

Solution for the network printer was, connected this plotter to LPT1 on one of the computer and shared it, when we do this, its does not require an IP address.

This sorted out the main problem and the network was up and working, this blog may sound that the work was simple, NO it was not an easy task, had to put double effort to complete it on time.

Prepared a comprehsive document for this network, hopping that users in the site will use when trouble arises, do you thing they will have time to go through this document, hope so ;-)

MCSE 2003 training
Presently I am doing my Windows XP client paper, more than the training the exams dumps provided is useful, it helped me in understading the network better.

Good nite have to complete the documentation and go to bed

Cheers- MSB