1. Suppose the datagram source allocates 12 bytes for this option. Then when the datagram leaves the source host, the RR option area will be like this:

7 12 4 0
0 0 0 0
0 0 0 0

2. At the ?rst router, the datagram may or may not be fragmented. The ?rst fragment (or the original datagram itself, if it was not fragmented) will be like this:
7 12 8 0
address 1
0 0 0 0

where "address1" is the IP address of the outgoing link at the router.

3. At the second router, the ?rst fragment (or original datagram) will be like this:
7 12 12 0
address 1
address 2

4. At the third and all later routers (which don't exist in this assignment), no additional IP addresses would be recorded because there is no room. These later routers can tell there is no room because the "pointer" value (12) is equal to the available space value.