FirstDigest » Cisco

InterVLAN routing using Private VLANs

Calin — Fri, 23 Sep 2011 13:04:06 +0000

Private VLANs is one possible solutions for service providers to offer secure connections to their customers and avoid inter-vlan communication in the same switched environment.

I’m sure that you heard (and most probably practice already) InterVLAN routing. When it comes to Private VLANs the routing part may be a bit tricky. Keep in mind that this is not something that I would recommend to use as a standard in a productive environment, but for things like Cisco exams (e.g. CCIE R&S) or last resort solution, [...]

Interface software loop

Calin — Tue, 30 Aug 2011 08:13:13 +0000

If you ever worked in an environment where you have to deal with leased / dedicated lines provider by your SP (service provider) then you know that whenever it’s a problem on the line they request, if possible, to put a loop on the line from one end toward the other end, so they can do some measurements. Usually from my experience with SP, this is a standard approach in case that they don’t know exactly what problem is with your line or where the [...]

Cisco IOS release naming

Calin — Mon, 11 Jul 2011 13:42:26 +0000

Most probably you already know this, but for those who are interested, here is a list of the letter definitions for Cisco IOS release trains. In more human terms, if you have loaded an IOS image like c2900-universalk9-mz.SPA.150-1.M5.bin, what those letters (in this case SPA) mean:

A = Aggregation/Access Server/Dial technology B = Broadband C = Core routers (11.1CA, 11.1CT, 11.1CC) D = xDSL technology E = Enterprise feature set F = Feature Specific enhancements (11.2F) G = Gigabit Switch Routers (GSR) H = SDH/SONET [...]

Cisco IOS: single user access in CLI configuration terminal

Calin — Wed, 07 Jul 2010 10:00:17 +0000

Usually big companies with large network have a dedicated department which deals with all the network configuration. The problem that I have in mind is when this department is splitted over large geographical areas (e.g. some colleagues in Europe, some in Asia and some in America) it may happen that more than one colleague is working on the same device at the time.

This can cause overlapping configuration or other problems, due to the fact that more than one config is applied [...]

Cisco: Use TTCP to test together with TTCPW or JPerf

Calin — Tue, 27 Apr 2010 13:27:26 +0000

In one my previous posts, I shown you how to test a connection using a hidden Cisco IOS tool called TTCP. A few days ago I run into an issue. I had to test a TCP connection to a remote Cisco router, but I had not other router on which to initiate the TTCP connection. As explained in Testing TCP Connection [...]

Cisco tips: Track down communication issues – Part 2

Calin — Tue, 16 Mar 2010 11:58:12 +0000

In the 1st Part of this series, I’ve described the most common steps that you should follow to troubleshoot a total lack of communication between a Layer 2 device (Cisco switch) and an end user connected device. As I promised here is the second part, in which I’ll try to show you what you can check when you have no problem with connection, but still you encounter a degradation [...]

Cisco tips: Track down communication issues – Part 1

Calin — Mon, 15 Mar 2010 14:55:51 +0000

You know how sometimes you plug in everything, configure device / ports and then the un-expected result is “not working”. Then you start to troubleshoot, which is a good point, but very important is where are you looking for the root cause of your issue.

A lot of people who have communication issue start by issuing a ping from one end to the other one. This is a good approach when somebody is reporting service issue (e.g. my webserver doesn’t work) as with the ping [...]

Cisco: How to determine the serial number of hardware components

Calin — Fri, 12 Jun 2009 09:32:20 +0000

Some days ago I had to check for the serial number of a faulty fan tray that need to be exchanged in C6500 series. Now most of you I believe know the commands “show version” or “show hardware” which will get all the information that you need most of the time, but not always. I decided to put in this post some useful commands to identify the Cisco hardware components and their respective identifiers (serial nnumber) on different platforms.

I will use for my example [...]

10 tips that I can tell you about Cisco CCIE exam preparation

Calin — Fri, 20 Mar 2009 15:09:34 +0000

Since now I’m closer than ever to my CCIE lab exam, I thought that it would be a good opportunity to share some of my preparation experience with you. Even if this post is focused of the CCIE preparation, I believe that you can take my advices into consideration even if you are preparing for some other exam.

As most of you, when I started the preparation I searched on the Internet about some advices like what should I read, how much time to [...]

Cisco: How to achieve network redundancy with 2 interfaces

Calin — Thu, 19 Mar 2009 20:09:37 +0000

Sometime ago, during my preparation for Cisco CCIE certification, I encountered a task that I had to admit made me think a little bit, even I should see the solution from the first minute. The idea, at least as I see it, is that as much as you learn for some certification you start to see only the complex and painful part of the networking and this made me skip over the simplest solution. Something like, I learn to fly to the moon but I [...]