I created an Advanced Computer Networking course offered at Master's level which follows an earlier undergraduate course in networking (which I also created and teach).
I'll offer some insights, suggestions and thoughts, but they will just be off-the-cuff rather than a formal curriculum plan (I've done enough of those).
The first thing to start is to not assume that the students have fully absorbed and are usefully fluent on everything in Tanenbaum! Start with revision, focusing on those parts of the material that would be essential to grasp to move on to the advanced material. Do not revise by just going through it again, but do it through asking questions and raising problems so they can determine if they understand the material well enough. In particular I brought out routing at the network layer as being critical, as well as multiplexing at the transport layer, as well as the whole 7 layer model again.
I then focused on larger issues that students may not have encountered when administering their own machine. Things that happen at ISP level and internet backbone level, such as BGP, AS numbering and the protocols and databases involved.
A lot can also be done with security, such as the law and ethics. What is a network administrator permitted to do and when does managing a network exceed the authority allowed (such as entrapment). I looked at honeypots for example, as well as logging.
In a more advanced course I also put more emphasis on self-learning. Things such as monitoring media for incident reports; making presentations on security incidents over the last 12 months, for example.
In terms of network management SNMP and tools that use it can be covered in more detail, including network discovery, network mapping and so on. As practical work I get them to program an SNMP tool to learn about the object encoding mechanisms and also about packet capture.
I have more ideas, but this might get you started.