GNS3 has been a crucial tool used by many network engineers to emulate computer networks. It has proven to be fundamental studying for all network certification levels such as CCNA, CCNP and CCIE. It has been crucial for network design validations within many companies. With the news of Cisco’s VIRL, many said that GNS3 will disappear, but that doesn’t seem to be the case. GNS3 is going through a major redesign and needs the help of all the engineers that it helped over the years.
At Cisco Live in Orlando I had the chance to demo the Virtual Internet Routing Lab (VIRL). It is Cisco’s answer to GNS3 or Junipers’ Junosphere using virtualization to create virtual network topologies. This tools will be as revolutionary as GNS3, but at a much larger scale. It is an awesome tool that can be used for certification studying but also to validate production designs. Everyone I spoke to couldn’t wait to get their hands on it, including me!
Reading the IPv6 Configuration Guide (Implementing Traffic Filters and Firewalls for IPv6 Security), I came across a little known fact that seems to be very important when configuring IPv6 access-lists on IOS.
Usually when I configured an IPv4 ACL, I explicitly defined a deny ip any any at the end, which seems like the best practice. But what happens when you do that same thing with IPv6 ACLs.