FirstDigest » Tips&Tricks

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, [...]

Would you do such things to an ISR 819?

Calin — Fri, 09 Sep 2011 10:03:41 +0000

Lucky there is a big disclaimer at the beginning of this video. Otherwise I would be tempted to test such things and then plug it in to see if it still start (at least) and run.

It’s a nice commercial from Cisco, but to be honest I feel bad for this poor device:

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 [...]

How to connect Vyatta to Cisco using VirtualBox and GNS3

Calin — Tue, 17 Aug 2010 10:40:28 +0000

“Vyatta is a software-based, open-source, network operating system that is portable to standard x86 hardware as well as common virtualization and cloud computing platforms. By deploying Vyatta, users benefit from a flexible enterprise-class routing and security feature set capable of scaling from DSL to 20Gbps performance at a fraction of the cost of proprietary solutions.”

Shortly, you take this piece of software, install it on a x86 machine (any decent PC with quality network card will do) and have yourself a network [...]

Cisco 2900 – Interface related chassis modification

Calin — Mon, 09 Aug 2010 11:41:50 +0000

The Cisco Enhanced EtherSwitch Service Modules seen above, expands the router’s capabilities by integrating Layer 2 and Layer 3 switching feature sets identical to those found in the Cisco Catalyst 3560-E and Catalyst 2960 Series Switches.

The new Cisco Enhanced EtherSwitch Service Modules are the first modules to take advantage of the increased capabilities on the Cisco 3900 and 2900 Series Integrated Services Routers. Additionally, these service modules enable Cisco’s industry-leading power initiatives, Cisco EnergyWise®, Cisco Enhanced Power over [...]

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 [...]