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IPv4

How to configure an IPv4 GRE tunnel to carry IPv6 traffic

Continuing the review of the TSHOOT Topology, on the IPv6 network map there is a GRE tunnel that is configured between Router 3 and Router 4. This tunnel is in place to allow IPv6 traffic to traverse the 10.1.1.8/30 IPv4 network. So, while reviewing the IPv6 tshoot topology, I decided to try out the tunnel configuration.

There are several ways to configure tunnels to allow IPv6 traffic to traverse IPv4 networks (and vice versa). This post will be focusing on a GRE tunnel configuration. If you want to review the other ways to create tunnels, i.e.  Automatic IPv4-Compatible IPv6 Tunnels, IPv6 Rapid Deployment Tunnels, and Automatic 6to4 Tunnels, I've included a link below to a great resource on Cisco's website that shows some great examples of other tunnels.

I threw together the following network diagram to provide a visual of what we are configuring: 

IPv6_GRE_Tunnel2

Pop Quiz - Subnetting Challenge

Here are some subnetting questions to get the synapses firing on a Friday:

1. What range of addresses are encompassed by the summary address 10.45.128.0/18?

A) 10.45.128.0-10.45.128.255

B) 10.45.128.0-10.45.128.128

C) 10.45.128.0-10.45.191.255

D) 10.45.128.0-10.45.129.255

2. You need to configure a new branch office LAN with at least 812 usable IP addresses. The site desktop manager wants a single range of addresses to make it easier to configure the gateway and subnet mask on the computers and printers being deployed. Your company uses the 10.0.0.0/8 address space for internal networks and the subnet 10.128.0.0/16 has been reserved for new branch office LANs (WAN links are in a different subnet). Starting with the first available network in the reserved range, what is the most efficient subnet and CIDR mask for this new branch office?

A) 10.128.0.0/16

B) 10.128.0.0/23

C) 10.128.0.0/21

D) 10.128.0.0/22

3. The following access list is filtering traffic:

access-list 1 deny 192.168.64.0 0.0.31.255

access-list 1 permit any

Which of the following addresses will not be dropped? (select all that apply)

A) 192.168.64.1

B) 192.168.92.1

C) 192.168.96.1

D) 192.168.127.1

Answers after the break:

Subnetting 101

Have you always wanted to learn how to subnet IPv4 addresses? Already know how to subnet, but want to improve your speed or accuracy with subnetting? You aren't alone! I've met many people that want to improve their skills in the "art" of subnetting, so I decided to do a quick post to share some resources on how to do just that.

How to subnet a network (pdf) - Beginners guide to subnetting, somewhat technical though.

How to subnet an address the easy way - This page provides a handy shortcut to figure out what your network address is based on the subnet mask. 

How to subnet a network - Introductory level, somewhat in-depth on the binary stuff, but doesn't provide many examples.

Free IP Address Management from Infoblox

infoblox_logo.jpg

IPAM is typically an acronym you don't hear until you start working on large networks. Most small to medium size networks have either a couple large networks (i.e., "the 10.0.0.0/8 network is over there, and the 192.168.0.0/16 network is over there...") or a few /24 subnets like 172.16.1.0/24 for Data, 172.16.2.0/24 for IP Phones, etc. 

However, when you start having to design solutions to integrate with hundreds of remote sites connected via a massive mpls network, multiple redundant data centers, and several campuses with dozens of buildings all interconnected, it becomes challenging to know where 10.37.225.64/28 is located without a spiffy higherarchical IP address design, great documentation, or just plain crawling the network with traceroutes and "show ip route" commands. So because of all that, engineers that work with large networks rely on IPAM to help organize and allocate IP addresses.

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Dr. Radut