2018 is the year my CCNP certification is set to expire. I have given myself the challenge to recertify and take this opportunity to blog about the technology fundamentals. I hope my notes in this blog series help others taking the exam in the future!

The series is still a WIP. I will be making incremental updates live as I am taking the opportunity to test my static blog system.


  1. Identify Cisco Express Forwarding concepts
  • FIB
  • Adjacency table
  1. Explain general network challenges
  • Unicast Unicast traffic is 1:1. Addresses are broken up into classes: A, B, C. IPv6 networks do not use classes. Globally routeable networks use 2000::/3 prefix. Unicast doesn’t scale well. Other methods for 1:M delivery
    • Broadcast Broadcast traffic is traffic send to a subnet’s broadcast address (address with all 1’s in the host portion of the subnet with mac address FF-FF-FF-FF-FF-FF). This traffic is scoped at the layer 2 boundary.
    • Multicast Multicast traffic is another form of 1:M propagation. Traffic is sent to a class D ( where peers will be waiting for information destined to that address. IPv6 hosts use the ff00::/8 prefix.
    • Anycast An anycast delivery is a 1:nearest system. An IPv6 host will transmit to an anycast address and the closest host to it will receive the stream.
  • Out-of-order packets Out of order packets is the phenomena where packets do not arrive in the order they were transmitted. The protocols can handle this by ignoring the packets that arrived too soon but at a cost of retransmitting. Out-of-order packets significantly slow down connection speeds.
  • Asymmetric routing Asymmetric routing can happen when return traffic (like traffic that has been loadbalanced) does not return down the same path it went out on. At small scale this may not be an issue but when transmitting lots of data and when the access switches are missing the relevant mac address entries for the destination hosts the switches will start doing excessive flooding.
  1. Describe IP operations
  • ICMP Unreachable and Redirects
  • IPv4 and IPv6 fragmentation
  • TTL
  1. Explain TCP operations
  • IPv4 and IPv6 (P)MTU
  • MSS
  • Latency
  • Windowing
  • Bandwidth-delay product
  • Global synchronization
  1. Describe UDP operations
  • Starvation
  • Latency
  1. Recognize proposed changes to the network
  • Changes to routing protocol parameters
  • Migrate parts of the network to IPv6
  • Routing protocol migration