Confusing Exercise and Solution 11.2
1) X and Y are confusing. From the exercise they look like ordinary variables. That's ok till we get to the solution there appears 2 new addresses: 172.16.Y.0/24 and 192.168.X.0/24. In the exercise we are given 2 new subnets, but solution shows us that there should be 4 (which is not true). I would like to suggest to re-phrase "Where X and Y are unique to the lab/classroom" to "Where X and Y are set to a value to ensure that they are different from the possible currently set subnet on the corresponding interface" (it is just an example, it can be done better);
2) Why making routes persistent if we anyway set the aliases temporary? It would be better and simpler to just give the route command which will set up temporary routes and should work on all distros (in this way eliminating the need to give separate instructions for each distro). Yes, knowing how to make routes persistent is important, but in this case the exercise itself must ask for persistent aliases;
3) There is no need for 2 new routes for each system, 1 is enough. Also I find confusing <ADDR-*> notation. It may seem obvious, but still, I would note that these are the addresses of the default subnet on the corresponding interface.