Simulating a Host in Dynamips/GNS3

For those who don’t know what Dynamips is …. aaaaaaaahhh … it is a very cool piece of software that allows us to emulate any Cisco router and even the PIX. It is a very useful tool for experimenting with Cisco-based networks and one of the cheapest ways to prepare for the CCIE lab. I use it for the later purpose and also to get some hands-on practice with various networking technologies. GNS3 is a very cute graphical front-end to Dynamips which is more suited for adhoc experimentation due to the simply way you can create any topology by dropping devices and connecting them. I was watching a video class on IPv6 when something the instructor said hit me “… without the ipv6 unicast-routing command, this router will not function as a router”! …. immediately I fired up my copy of GNS3 and to simulate a host, I added a router and proceded thus to make it a ‘host’ 1. Disabled routing [no ip routing in global config mode] 2. Configured and IP address and subnet mask on an interface and enabled the interface. 3. Gave the router a default gateway by typing ip default network a.b.c.d where a.b.c.d is the IP address of the router to which this ‘host’ is connected. An viola! I had a host I could ping from. This enables me to simulate a LAN connected to the router … definitely a more elegant way that using loopback addresses which is what I was using until now. So experiment away and drop me any suggestions.