I'd like a little clarification regarding GRE encapsulation.
From the way I have always understood it, an IP packet is encapsulated into/by a GRE packet that has a 20 byte header. But nowhere in that header exists a source IP or destination IP address field (The tunnel source and destination addresses would be the ones of interest to GRE). So, how does GRE forward the packet to the tunnel destination?
Moreover, it seems that, logically speaking, GRE sits between IP (network layer) and the data link layer. Is that correct?
I have yet to find any web link, including Cisco's, that really explains the nuts and bolts -- the mechanics -- of GRE to the degree I am describing here. Does anyone have one?
It's good to hear from you, too.
For the last several months I've been having a lot of other tasks to do and I have little time to participate in the forum.
However, when I find some time, I always return to this site because it's an excellent place to find challenging problems.
I found a good stuff for you: