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A cache by peetu, adopted by mandello Send Message to Owner Message this owner
Hidden : 10/18/2004
4.5 out of 5
1.5 out of 5

Size: Size: micro (micro)

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Geocache Description:

This mystery requires some knowledge about IPv6. Either you know it, or you can learn it.

The current Internet addressing is based on Internet Protocol version 4 (IPv4) addresses. These addresses are 32 bits long and are usually described in format a.b.c.d, where each of the letters describe an 8-bit part of the address. E.g. an address could be, which belongs to a host called

Even the theoretical address space is large and could support a huge number of hosts (you can generate 2^32 different IPv4 addresses), the practise is something different; when parts of the address space is given to different companies and organizations, not all the addresses are used and a huge part of the whole address space is wasted.

During 1990's, the next generation of the IP addresses was designed. This address space goes with the name IPv6. IPv6 addresses are now 128 bits long, providing much more addresses than IPv4. We can now generate 2^128 different addresses from that address space.

In a usual case, IPv6 address is divided into two 64-bit parts. The prefix part, 64 first bits, is used for routing in the network and the suffix part, 64 last bits, is used to identify the hosts interface in the network. This means that the routers in the Internet use only the first 64 bits to determine the next router where the packet is delivered when it travels towards its final destination.

When a computer connects to an IPv6 network, it can use either stateful DHCPv6 where the host is assigned an IPv6 address by the server in the network or stateless address autoconfiguration where the router gives only the address prefix for the host and the host itself generates its IPv6 address.

The neighbor discovery process [RFC2461] is used to determine the link layer addresses for hosts. This link-layer address information is needed to deliver the packet over the cable to the destination host. Usually, the underlying network is an ethernet network [RFC2464].

The RFC-numbers refer to IETF standards ( They may help in this task if you are not familiar with IPv6 stuff.

Your task: You are the router at the border of a local network. An IPv6 packet arrives from the Internet. The packet has a destination address and you can figure out that the prefix points to your local network. The destination address is:


You know that the cache is located at that computer. Find out where the computer is. And find the cache.

We give you part of the coordinates: N60 E024 49.yyy. You have to find out the rest of the location information.

Check your solution from geochecker.

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