Currently viewing the tag: "Routing and Switching"

How to monitor IP SLA with free tools

By On February 18, 2009 · 5 Comments

Lately I saw an increasing interest for IP SLA monitor and analyze of the data output. I believe that you already know that you can do IP SLA monitor with a lot of tools from the most expensive ones which include support and assistance to the free ones like MRTG or RRDTOOL. From the statistics that I have, more than 50% of the network engineers interested in this tools have a problem either with the money (low budget or the on and on “we do [...]

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Cisco: Quick IOS check in 4 simple steps

By On February 10, 2009 · 1 Comment

This post is rather for the beginners in Cisco’s world than for advance professionals, but still I encounter situation when IOS image was corrupted even if it was uploaded to the device by a network guru. Why? It’s quite simple! Because you can be the master of the Cisco networking,  but still sometime you cannot control the device behavior or the transport of the packets to destination.

The problems is that in case of a corrupted IOS image being uploaded on a Cisco device, and [...]

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Cisco: How-to get notifications for IP SLA monitor using EEM

By On February 8, 2009 · 4 Comments

In some previous post, I explained how to configure a basic IP SLA monitor for checking the round-trip time between two Cisco routers. Because in the comments of that post I have been asked how you can get e-mail notification for IP SLA monitor, I have decided to write another post to extend a little bit this topic.

To accomplish e-mail notification for IP SLA monitors we will use [...]

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Cisco: FWSM CPU stress test how-to

By On February 6, 2009 · 2 Comments

Sometime ago I had to do a stress test for a Cisco FWSM (Firewall Service Module) to see how the resources are consumed and if some potential traffic can temporarly affect the behavior of this device. For those of you who have don’t know what is a Cisco FWSM, here comes the definition: “Cisco Firewall Services Module (FWSM)—a high-speed, integrated firewall module for Cisco Catalyst 6500 switches and Cisco 7600 Series routers—provides the fastest firewall data rates in the industry: 5-Gbps throughput, 100,000 CPS, and [...]

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Cisco: 6 best practice security tips for BGP

By On February 5, 2009 · 1 Comment

As we all know, in today’s digital communication world, there is a very big possibility that your network is or was target for a malicious activity. BGP is one of the most targeted routing protocols when we are talking about network attacks.Why? This is quite simple. BGP is your connection to the exterior world (peer networks, Internet and everything which is outside your LAN/MAN), so it is somehow normal to be the main target of the conducted attacks. If in case of the WWW, DNS, [...]

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Cisco: IPv6 basics and configuration how-to

By On January 27, 2009 · 4 Comments

Today, I had to deal with IPv6 configuration for my CCIE preparation and I said to write a small tutorial about IPv6 for it’s basic stuff. First of all IPv6 is not more complicated that IPv4, it just look like it is. Second, and this is my personal opinion, I think that as long as IPv4 will be on the market and things like NAT can overcome the problem of  IP addresses being exhausted, IPv6 will not be implemented on a large scale. Let’s be [...]

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Cisco: Use CBAC to achieve firewall functionality on router device

By On January 19, 2009 · 4 Comments

Sometimes, because of cost saving usually, the network engineers are forced to use a Cisco router as a firewall (instead of Cisco PIX or ASA). One of the big difference between router and firewall devices is that the ports have different characteristics. If on routers, ports are permitting by default traffic of any packets in and out, on the firewall devices, any packets are denied, if not explicit permitted.Also firewalls look at ports as Inbound at Outbound while for routers this has no meaning.

Anyway [...]

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Cisco: Engineer’s trick to avoid suboptimal path

By On January 16, 2009 · 9 Comments

I was explaining in the previous post what is the difference between optimal and suboptimal path and how to avoid the use of not such a good path in your routed environment. Also there I presented this so call “dirty trick” you can use to force the routing protocol to choose the path that you want, based on the Administrative distance modification.

As I said there is another way (for sure more than one) to do it, using [...]

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Cisco: Dirty trick to force optimal path in routed environment

By On January 15, 2009 · 3 Comments

Everywhere in the world people try to find the optimal path to achieve something.If we speak about roads, trips and in our case networking, choosing the best path to an end point can have only advantages.

I took the term optimal / suboptimal path from the routing issues that can appear in the OSPF network environment and which are called by the experts suboptimal routing. What I want to explain here, maybe you already seen it, is that in some network environment the best path [...]

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GNS3: How-to save multiple topology configurations for good

By On December 19, 2008 · 4 Comments

GNS3 is an extremely useful tool if you are using Dynamips to emulate Cisco devices. It is a graphical environment in which even a newbie can do complex configuration by clicking and dragging routers, switches, connections into a topology that can be saved.

The problem that occurred to me in the past (and maybe to you also) is the following. Let’s assume that we create a configuration with routers named R0 and R1 and you save the topology config and also the routers config (“copy [...]

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