Yahoo! we are now on the last part of the 15% of the exam which is network fundamentals.The last topic is to compare and contrast the following:
1.15.a Global unicast
1.15.b Unique local
1.15.c Link local
1.15.d Modified EUI 64
Let us start with
1.15.a Global unicast – it is the IPv4 counterpart for the public IP address. It means that it is the only IPv6 address routable to internet. How to identify this? You can identify this if you see an IPv6 address with a network prefix of 2000::/3
1.15.b Unique local – it is the IPv4 counterpart for the private IP address. So it is not routable to internet.We can identify this if we see FD00::/8 as a network prefix
1.15c- Link local – it is the most talk about ipv6 address because it is the IP address which has no IPv4 counterpart. It is automatically-generated unique address or we can manually configure or hard code it. Link local address is used as next hop IP address in routing.
How to verify if you got a self-generated link-local address? First, we need to know by heart that link-local address has a network of FE80::/10. I’ve got this Filipino mnemonics that is “LL address–> 80 years old na si LoLo pero may 10M. ” I used mnemonics for me to know it by my heart, the IP address, types and concepts are things that we should know by our hearts. However, we just don’t need to study the network prefix of link-local address. We must also know it by our hearts to get the EUI-64 address. So link local address is comprised of Network part + EUI-64 address as the host part.
1.15d Modified EUI-64 address- If ever you check the curriculum of CCNA exam, I interchanged multicast and Modified EUI-64 address. For better explanation of link-local address as well. The first question that comes with my mind is the word ” Modified”.So it means there is original EUI-64 and there is modified EUI-64. Upon reading the RFC documenrs it states that Modified EUI-64 was derived from IEEE EUI-64 but the concept is just the same. So, let us relate this EUI-64 to link-local address. First, what I am showing is EUI-64 and then we are going to relate it to Link-Local address.
As you observed, the main reference of the EUI-64 is the MAC address of the device. The MAC address is divided into two. First part is OUI ( Original Unique Identifier) which is assigned by the vendor and the 2nd part is the NIC which is the Network Interface card. EUI-64 is formed by two steps:
- Divide the MAC address into two
- Insert FFFE in the middle to form a 64-bit IP address from 48-bit MAC address
- Invert the 7th bit (from 0 invert to 1) or ( from 1 invert it to )
For the third step, our example shows that the first eight bits represents hexadecimal “01” and if we represent it to binary it would be 00000001 and the 7th bit is zero and the since it is part of protocol to invert the seventh bit then it would be 00000011 so that is the reason why it went form hexadecimal 01 to hexadecimal 03 to represent the first 8 bits.
Hahahaha! I hope you understand my explanation.
1.15.e Multicast- there is no difference for the function or definition of multicast address from IPv4 and IPv6. The function is still to send a message to a particular group. You can verify multicast address if the network prefix starts with FF00::/8. In the world of routing, we send a packet e.g. “hello packet of OSPF” ( we will discuss this as soon as we go to routing protocols) via multicast address. For IPv6, there are specified multicast address that we need to know by our hearts which are you can see below.
|ff02::1||All nodes on the local network segment|
|ff02::2||All routers on the local network segment|
|ff02::5||OSPFv3 All SPF routers|
|ff02::6||OSPFv3 All DR routers|
|ff02::8||IS-IS for IPv6 routers|
We should take note that there are a lot of multicast address designated but these are the only few but popular that we need to know by our hearts. It may be harder for a newbie or beginner to memorize those multicast address because there are routing terms that needs further explanation.
Though I have already elaborated this on the previous post. An advantage of having autoconfigured address is the ease of use without dedicated server. Just come to imagine if there is a mismatch within the server and the router, we may troubleshoot it but it may required effort and minor headaches.
Anycast addresses allow you to send a message to a set of receivers but only one of them will receive it. The best way to interpret anycast address is to sending to the nearest receiver among the group.There is no clear identification of anycast address or we cannot identify them by knowing the network prefix but we can configure them. As much as I wanted to include the configuration in this topic but I think it may lead to “information overload” .
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