My weakness

I have decided to get the CCIE RS exam, because i think there is one way way to achieve one of my goal : be an expert.
After many hours learn and learn this is for me, my weakness in Networking (when i say weakness i.e the topics that i dont masterize very well topics where my motes can be under 10 of 20)
- Multicast routing (msdp, pim-sm, etc...)
- Ipv6
-QoS
- Pfr and Oer