 % Invalid interface. Use full interface name without spaces (e.g. Serial0/1) That's annoying, but we do what we must: Output Interface: fastetherneto/o Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to E80::214:6AFF:FEA2:D438, timeout is 2 seconds: Packet sent with a source address of FE80::212:43FF:FEB9 2C70 !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 0/0/4 ms Ping works just like you'd expect it to, though we had to include the source interface and spell it out. Why? Because the network for this IP address is the same on every interface-remember, it's a link-local address, SO the router will not forward it between interfaces. The real difference is the terribly long IPv6 addresses. We all like to rattle off IP addresses like we're some sort of savant. I'd venture a guess that for most of us, IPv6 will have us firmly believing in proper DNS usage. This is all well and good, but link-local addresses are dropped by routers, since those addresses are designed to be used only on the network on which they reside. What's the point of having a router if you can't forward packets from one interface to another? To forward packets, by definition, each interface on the router needs to be in a different network. In my opinion, this is where IPv6 can become a network admin's dream. IPv6 allows you to address interfaces without assigning a host address. Since we can create an address by translating the MAC address into a EUI-64 format, we can quickly Chapter 37: IPv6 connect devices just by telling them what network we're on. An example of this is shown in Figure 37-1. AAAA: AAAA : AAAA :1:/64 Figure 37-1. Simple IPv6 network with two routers Here on R1, we've already got a link-local address, but as we've covered, that's almost useless for real-world networking. With the ipv6 address address/mask eui-64 interface command, I'll assign a network address to the F0/0 interface. Let's say that I've been allocated the AAAA AAAA: AAAA: : /48 address block. I'll start by using the :1: subnet: R1