Manual summarization with any routing protocol

Rule of thumb:

• Internal network summarization: Should always occur on the distribution layer towards the core layer.
• Branch network summarization: Should always occur on the branch edge towards the HQ.

For EIGRP:

• More information about EIGRP summarization can be found at 1.3.a Adjacencies

For OSPF:

• More information about OSPF summarization can be found at 1.4.a Adjacencies

For BGP:

• More information about BGP aggregation (summarization) can be found at 1.5.e Convergence and scalability