Hello,
The source and destination addresses of the encapsulated packet are indeed those of Lisa and Homer. However, the IPv6 addresses in A and B are needed for routing. As is written in slide 27, A’s IPv6 default route is 2001:1:aa::1, so when A receives an IPv6 packet from IEW, it forwards it by default to the channel connecting A and B. In other cases, A might be connected to multiple tunnels, so it needs to know through which tunnel it should send the packet each time.
