Hello Daniel
When configuring an IPv6 address on an interface using a command like ipv6 address 2001:192:168:12::/64 eui-64, it doesn’t take resources to “learn each burnt in mac address”. When you apply the command, the address is set. The idea is that it would take much longer for you to statically assign IPv6 addresses to all hosts within your subnet, especially if you have, say, 1000 hosts. Would you want to configure them all by hand? And what happens if you make a mistake and assign the same address to two devices? You can see that when you scale up the number of hosts, the ease of the EUI-64 option becomes apparent. If you have only 5 hosts, sure, statically assign them no problem. But for many more, EUI-64 is definately an advantage.
Take a look at this post:
If you wanted to separate this address into two subnetworks, you could do this:
- 2001:1234:2222:2411::/65
- 2001:1234:2222:2411:8000:/65
But typically you wouldn’t use a prefix like /65, you’d want to separate it at a full hex digit, which means prefixes typically are multiples of four. So you would probably separate it into 16 subnets like this:
- 2001:1234:2222:2411::/68
- 2001:1234:2222:2411:1000::/68
- 2001:1234:2222:2411:2000::/68
- 2001:1234:2222:2411:3000::/68
- 2001:1234:2222:2411:4000::/68
- …
- …
- 2001:1234:2222:2411:E000::/68
- 2001:1234:2222:2411:F000::/68
For IPv6, the next hop always uses the link-local address of the next-hop router, along with the exit interface. More information can be found here:
I hope this has been helpful!
Laz