is an independent personal blog of Gabor Kis-Hegedus focusing on advanced, unusual or under-documented features of Cisco IOS, the software running on routers and switches produced by Cisco Systems.
July 4th, 2012 | Tags: , ,

I like this platform very much, but a while ago we can buy ASR100x and ISR G2 routers. So Cisco announced the end-of-sale and end-of-life dates for the 7200 Series Routers. If you whish, you can buy your last one at September 29, 2012.

January 5th, 2012 | Tags:

I would like to whish a Happy New Year to every Network Engineer out there:)

UPDATE: I completed the CCIE R&S Written Exam in December 2011, so I will begin to study for the LAB. I already created an MS Project Plan (According to this, I will take the LAB in August).

I will use only INE materials, RFCs, books, Dynamips, IOU and rack rentals – hope it will be enough:)

May 28th, 2011 | Tags: , ,

Well, this will be a story about a voice gateway, which is restarting every 12th day:)
For mounts we didn’t notices the problem, because the router was quickly rebooted. After we implemented central logging (I will write about this a post), we received mail about the reboot. We begun writing mails to the Cisco TAC. Personally, I have always bad feeling, when I have to give a mysterious issue to the vendor’s support team.
This was however a nice job. I would like to include the final mail about the problem, because I think it is “funny”:) Of course you can imagine, that we had to escalate the problem many times, until we received the solution…but Cisco TAC, I like you.
Read more…

May 20th, 2011 | Tags: , ,

If you already implemented central logging, and you have also a Voice Gateway in your network, it is very annoying, that your logs are filled with ISDN-6-CONNECT/DISCONNECT messages, like this:

335414: May 19 19:07:49 CEST: %ISDN-6-CONNECT: Interface Serial0/0/0:26 is now connected to xxx N/A
335415: May 19 19:07:51 CEST: %ISDN-6-DISCONNECT: Interface Serial0/0/0:26 disconnected from xxx , call lasted 2 seconds
335417: May 19 19:08:18 CEST: %ISDN-6-DISCONNECT: Interface Serial0/0/0:27 disconnected from xxx , call lasted 871 seconds
335418: May 19 19:08:20 CEST: %ISDN-6-CONNECT: Interface Serial0/0/0:30 is now connected to xxx N/

You have an option however, to filter out these type of log messages with Message discriminator. Read more…

May 9th, 2011 | Tags: ,

If your core router’s configuration has more then 5000 lines, issuing a show run is not too fast. For example on our 7200 with NPE-G1, it can take up to 5sec. I don’t like waiting, so I was happy, when I found the “Configuration Generation Performance Enhancement feature”. The configuration is very straightforward:

parser config cache interface

But what does this feature do? Cisco says:

Until the Configuration Generation Performance Enhancement feature was introduced, NVGEN always had to query the entire system and could generate only a total configuration. The time required to process the running configuration creates performance problems for configuration management, because completion of the NVGEN operation can take many minutes.

The Configuration Generation Performance Enhancement feature reduces the execution time for NVGEN processes and is especially useful for managing large configuration files that contain numerous interface configurations. This feature provides faster execution of commands that process the running system configuration by caching interface configuration information in system memory, and by retrieving only configuration information that has changed.

If you are using IOS 12.3(7)T or newer, and the router has enough memory, you can speed up the things. After I configured the feature, the sh run command was ready in less then a sec.

April 24th, 2011 | Tags: , ,

One of our customer asked us to change the destination TCP port on our last MPLS PE router, because they don’t want to change this on every remote POS terminal. This seems to be easy if the destination IP address is on the router, but the traffic is flowing through the router. I created a GNS3/IOU lab to demonstrate, and tested the solution.


Read more…

April 23rd, 2011 | Tags:

Hi everybody!  So this is the new blog. I will upload the content of the old one soon. (update:


Right now, I’m preparing for the CCIE R&S written 🙂

Code test