Sep 10

CDP for your computer

I recently had a room that was in the office that was remodeled into a sea of cubicles with all new wiring. The maintenance crew built the cubicles and ran all of the CAT5 drops to each desk. Two different groups were being merged into the same room, yet needed to keep their original VLAN so they could retain their access into the secure areas of the network.


When I got the seating chart I asked the maintenance guys for the wiring diagram and what switch port each desk connected to. They had nothing for me so I headed to the desks to get it figured out. My coworker educated me about a piece of software called CDPR. With CDPR I was able to connect to the jack at the desk and find out what port on the Cisco switch I was connected to.

You place this software on your computer, go to that directory from a command prompt and execute the file. If you have multiple NIC’s it will ask you what NIC to use. After you select your NIC, you simply have to wait until it receives a Cisco Discovery Protocol (CDP) packet from the switch and then it will tell you the switch name and the port. When we did this room, we shortened the CDP timers so it would advertise more often. Below is an example of what it looks like to run it and select your NIC.

C:\>cdpr
cdpr – Cisco Discovery Protocol Reporter Version 1.0.7
Copyright (c) 2002 – MonkeyMental.com

1. \Device\NPF_{FCFF8C2B-958F-4080-A1B9-0D464447009F} (Intel(R) 82577LM Gigabit
Network Connection)
2. \Device\NPF_{D27E2C86-F323-4D6D-8451-1AA70F0F6064} (Microsoft)
Enter the interface number (1-2):

You can get your copy of CDPR follow the link to MonkeyMental.com.

I thought this was a really slick tool and was very happy my coworker let me know about it.

Have you ever used this before or do you have a tool similar to this? If so, let us know!!

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Sep 03

Can you get your fan tray out?

Network hardware vendors are challenged with the need for a fan tray in their chassis. The fan is something that probably won’t go away for a very long time, yet it’s a piece of equipment that can fail. Some chassis have fan trays that are very easy to get out and replace, the Cisco ONS 15454 is one of those chassis. The Cisco ONS 15454 has a fan tray that is removed from the front and it simply pulls out.

Other chassis have the fan tray in a location that cause a problem with being blocked by the data cables. The Cisco 6513 is a great example of a fan tray that can easily be blocked by the data cables. If you are not familiar with the 6513, the line cards are horizontal in the chassis. The air flow needs to go side to side, so the fan is on the left. To avoid the fan tray, all data cables would need to come from the right side of the switch to be connected. This can be a very difficult challenge due to the quantity of cables that the 6513 can support.


On almost all of the network devices that I have seen, the vendor has done their best in the placement of the fans. They usually don’t have a choice on the location of the fan. If it was a different chassis design, then the fan would be in the way somewhere else.

I believe that it is our responsibility to correctly run the cables to avoid the fan tray. I have spent hours labeling and disconnecting cables just to replace a failed fan tray. If the cables were run correctly, the fan should be removed and replaced with out disconnecting any cables. No outage should ever be required to replace the fan tray.

Here are a few chassis that I have seen with very good Fan tray design.

Cisco Nexus 7010
Cisco ONS 15454
Brocade MLX-16

Here are a few chassis that can be challenging to cable and avoid the fan. Maybe the location of the fan tray could be better, maybe not.

Cisco 4500’s
Cisco 6500’s
Cisco 7600’s
Brocade SX800

What chassis have you used that have good or bad fan tray locations?
Have you ever had to take an outage to replace a fan tray?
Please tell us about it!!!

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