We all have limited budgets these days. Long gone are the days of unlimited resources and uncontrollable expansion of the network, so it’s important that any network dude or dudette pay attention to the open-source world. Below is a list of stuff I use at…
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I assume you take every word I say to heart and that you’ve been using Dynamips/Dynagen for a few days now, right? Good. That’s a start, but let’s break down a simple lab to make sure everyone’s on the same page. I run my labs…
I’ve run across articles for these apps a thousand times, so I thought I’d get in on the action. Dynamips and dynagen are a pair of apps that make simulating Cisco routers very easy. I use them constantly at the office (and even at home…
I had an article a few weeks ago about the Cisco CSM, which is a load-balancer module for the 6500 series switches. This thing is a pretty good device, but monitoring the connections to each VIP and RIP is not very straightforward. If you have…
We’ve done some tracking with HSRP in other articles, but there are lots and lots of ways to use object tracking on an HSRP device. In our example network, we tracked the interface, and, if it went down, we decremented the standby priority. What if…
I like [tag]layer-3[/tag] [tag]switch[/tag]es. They give some great flexibility and bang-for-the buck, but most people overlook one issue with these things that can cause security problems. Most people configure the [tag]VLAN[/tag]s, put an IP on the VLAN interfaces, and put it in production, but the…
Cisco’s Content Switching Module (CSM) is an application accelerator. Or is it an application networking service module? I hate those fancy buzzwords — it’s a load balancer. It’s a module for the 6500 series switches that lets you load balance services in any VLAN and…
Most firewalls should block [tag]ICMP[/tag] requests to them, so how do you know that your router or server has layer-2 connectivity to one? It’s pretty elementary, actually, but I’ve found that not a lot of people know this trick. If you ping the firewall, it…
I’ve seen a thousand [tag]firewalls[/tag] in my time, and nearly all of them are poorly configured. The biggest culprit? No [tag]outbound[/tag] [tag]filtering[/tag]. I guess a lot of people think that firewalls are there to protect the network from the Internet, but that’s only part of…
Remember the article on router-on-a-stick? And the one on HSRP? Let’s add to that example network, shall we? Let’s make those routers into edge routers so they connect your internal network to the Internet with some size circuit. Let’s just say they each terminate DS3s…