CONVERT MAC ADDRESS INTO IPV6 EUI 64 64 BIT

A link-local address is always the first address configured using SLAAC.If you have duplicate MAC addresses on the same network something is already broken at the Ethernet layer. A duplicate MAC address on a network is not a normal accepted condition.Here are some points to help explain the implications: If the address that fails that process than it cannot be used. It is true that all unicast IPv6 addresses must go through duplicate address detection, and especially with locally managed MAC addresses, it is possible to get duplication. What about DAD?Īt this point some people wonder, well what about Duplicate Address Detection. The implication then is that, if neither network or host portion are likely to change, the address is consistent. Certainly it is possible to do that, but it implies that the Admin must do that intentionally, and therefore plan for it. Given the host portion of the network, it can be combined with any network prefix for a network, to which the interface is connected, forming a valid v6 address.Īs you can see, this method for calculating an IPv6 address does not really allow for any wiggle room in terms of changing the host portion of the address without also changing the MAC address, or more to the point the Ethernet address.Then again we flip the 7th bit in from the left: 0250:11ff:fe22:3344.The MAC is treated as EUI-48 and we plunk ‘fffe’ in the middle: 0050:11ff:fe22:3344.

To convert the MAC address to EUI-64 and IPv6 address:

The last thing to do is to invert the 7th bit in from the left, commonly known as the U/L bit, and we end up with 00-50-11-22-33-44.

We remove the fffe in the middle and scrunch the numbers together, like so: 02-50-11-22-33-44.

First we drop the network identifier fd9a:1111:2222:3333 which is irrelevant, since it pertains only to the network.To translate the above IPv6 address back to the MAC address: (That fact is only important in explaining why we always see ‘ff:fe’ in the address.) Because of the ‘ff:fe’ portion in the middle of this host identifier, we can also infer that it is based on the 48 bit MAC address of that interface, which is actually treated as an EUI-48 number when used to calculate an EUI-64 based IPv6 address. So the host portion really looks like 0250:11ff:fe22:3344, when you consider all 64 bits. It is important to realize that the ‘250’ portion is really a short hand way of writing ‘0250’. The second part, (host portion), 250:11ff:fe22:3344, is calculated by the host.īefore we look at the potential for change, let’s examine this part of the address. Ultimately this network portion of the address should be as unchanging as a static address that is manually entered.

It is possible, but in an environment like ours, it’s unlikely without advanced notification as this would affect firewall rules, and would even break manually entered static addressed systems without a fair amount of coordination. When might that change? It could only change have to be configured at the router, and it would result from a network admin, or somebody like that, deciding to change network addresses, which would then involve setting up the corresponding routes through the network. The network portion, (first part), fd9a:1111:2222:3333, represents the subnet and comes from the router advertisement. (See IPv6 interface identifiers or RFC 4291 for additional information.) In this case those are…

CONVERT MAC ADDRESS INTO IPV6 EUI 64 64 BIT

Like all IPv6 addresses this is composed of two 64 bit portions. What is a MAC derived IPv6 address, and does it change?Ĭonsider this arbitrary IPv6 address, fd9a:1111:2222:3333:250:11ff:fe22:3344. So here is what I meant when I said these are largely static. My contention was that EUI-64 based IPv6 addresses are largely static. During a recent meeting we had a discussion about how static or consistent SLAAC IPv6 addresses are in the context of EUI-64 based addresses.

Convert mac address into ipv6 eui 64