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In Part 2 of the GRE/IPSec tutorial series, you will learn how to encrypt the GRE tunnels you built in Part 1. Although I only show you how to create a hub and spoke topology, it is also possible to create a fully meshed topology or even a partial mesh. I highly recommend creating GRE tunnels from the branch to every datacenter in your organization.

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I first discovered GRE with IPSec about 4 years ago when a customer needed to transmit IPX and multicast traffic over his VPN. Since then, I have primarly used GRE/IPSEC tunnels for transmitting internal routing protocols over the internet.  RIP, EIGRP or OSPF can be used over a GRE tunnel just as though it were a point to point circuit. It is also very useful for multicast music on hold.

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In Part 1 of the Internet lab tutorial, we created a virtual "internet" using gns3. We built the infrastructure and configured a router to represent "The Internet" (ISP). This time, you will add switches and configure the internet routers at each customer site. Other tutorials will follow that use these two tutorials as a foundation.

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This tutorial will help you build a basic Internet lab using GNS3 as a WAN simulator. It  will be referenced by future tutorials such as how to configure GRE/IPSec VPNs, how to configure a DMVPN (Dynamic Multipoint VPN) and QOS.

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In previous tutorials, I showed you how to configure a branch office ipsec vpn and  how to configure nat overload on an internet router. This tutorial will combine the two.

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This tutorial will guide you through configuring a dhcp server on your router. There are many reasons to have a dhcp server on a cisco router. Here are a couple examples … your small office may not have a server to hand out ip addresses via dhcp or the branch may have IP Telephony and it is best to hand our addresses locally than on a centralized server across the wan.

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I ran into a strange issue with a Cisco ASA firewall today. The firewall was not passing traffic to the internal host although I had the static statement configured and access-lists allowing incoming traffic.

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If you are new to Cisco equipment, command filtering may be new to you. If so, it will be worth your time to learn these shortcuts. 

If you are a veteran engineer, you probably use filtering with every command and this tutorial may seem too basic for you. However, you may not know that you can search through your command output even after the command is entered, using the forward-slash…see below.

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A virtual private network (VPN) is a network that uses a public telecommunication infrastructure, such as the Internet, to provide remote offices or individual users with secure access to their organization’s network.  The following tutorial will show you how to connect two locations together with an IPSec VPN using pre-shared authentication.

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We all know dynamips is a great tool for creating virtual networks and testing router configurations.  However, I can never seem to really understand a concept unless I use it in a "real" scenario. I will show you how  I have started using dynamips as my personal internet router.

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