Magic IP not so magic

[u6zk6]

This so-called magic IP which is referenced in chapter 3 almost derailed me from finishing your book. I run native Ubuntu 16.04 and docker seems to assigna unique IP to each container, and it doesn't begin with 172.17.0.n.

So not only could I not use 172.17.0.1 anywhere, in nearly every place where it was used in the chapter 3 examples, I had to replace it with another IP address unique for the database or application-server container. What the book should have contained is how to find out which IP address that each container is assigned using for example the command.

$ sudo iptables -t nat -L -n

[sgnn7]

@matsbengtsson That's a great point! Sadly earlier in the book, service discovery is not in the toolset of the reader yet and I wanted to cover the lower level fundamentals. At the time of writing that, the generic host ip was in almost all cases 172.17.0.1 but it may not be the case depending on specific host setup . It doesn't excuse the problem but may add some light to why it was there and while I can't remember very well now, I believe (well, more "strongly hope") that I have some sort of cautionary note about it in the book.

Either way, thanks for the info here and I will keep this issue open for others if they have the same problem! I've also lightly edited your post to make the code/IPs stand out a bit more.