Blast From the Past - BBS.Techinvasion.net Recently as a project cleaning up some old files and software, I came across a software disk for an old BBS I used to run. This got my interest peaked as I wondered if there were still BBS systems Alive and well on the internet. Information on BBS systems was few and far between in my research and it took …

Rotary Pools for Semi-Static NAT / Port range Forwarding Cisco routers have a very robust network address translation feature set.The NAT software allows you to control translation with access-list, route-maps, and destination pools.With the wide array of commands, it is sometimes difficult for beginners and experts to figure out how to combine …

Content Based Access Control “CBAC” In the beginning God created heaven and earth, and then he created routers, so packets could flow from one part of the earth to the other. As he rested he looked down on his creation and smiled for all was good. Packets were flowing from one interface to another. Then as he beheld his creation he …

Introduction to access-lists part 2 In the second installment of our guide to access-lists we are going to talk a little about named access-lists, how they work, what the benefits are, and how using them allows us to create reflexive access-lists. Named access-lists are exactly what they sound like, they are an extended access-list that has a name …

Introduction to access-lists part 1 Today I would like to take some time and talk about security. I want to discuss access-lists, extended access-lists, reflexive access-lists, and CBAC or content based access control. Learning how to properly use access-lists is so crucial to becoming a good network administrator. They are vital to securing your …

Replace a running config without reloading The new Cisco IOS 12.4 train has many new features that any engineer will find useful; one of the features that fix a pain point for me is the new config options available in 12.4. Have you ever been in a situation where an entered configuration does not work as expected? Now usually you have to back out …

Working a lot! I have been working a lot lately, we are in the proccess of designing a new data center with all the ifs ands and buts included in that ordeal. I am in the proccess of writing several write ups. On spanning tree: “load balancing spanning tree using different trunks” BGP implementation and design considerations. IGP …

Encrypting GRE tunnels In our Last article we looked at creating GRE tunnels between networks to allow non routable traffic to pass between remote offices.� GRE tunnels are a great solution however the traffic passing inside these tunnels is not encrypted and thus could be intercepted by unauthorized parties. In this article we are going to look at …

Create a GRE tunnel between endpoints Many time it is necessary to link a remote office to your main site and today we have many technologies to accomplish this task. We have IPSEC tunnels, IP-IN-IP tunnels, and GRE or Generic Routing Encapsulation Tunnels. Each type of connectivity offers advantages and disadvantages. Some of these tunnels can …

Cisco 3750 Switches now include a time domain reflectometer! How many time have�you wanted to know how long a cable run was? Now if you are running cisco 3750 switches you can find out by issuing the following commands you can see how long that cable run really is. Switch# test cable-diagnostics tdr interface gigabitethernet0/2 TDR test started on …