OSPF - Subnet Summarization to Reduce Routing Table Size

Hi,

We have Fortigates (FortiOS 5.4.5) running at multiple locations using site-site VPNs and OSPF dynamic routing. Also, at each location, there are multiple subnets (interfaces) configured.

When we look at the routing table it's getting excessively large. Fortunately, each location has a uniform IP assignment, which would allow all of the subnets to be summarized into one larger network.

I've tried several different combinations of CLI: Config Router OSPF -> Config Area -> Config Range -> Set Prefix and Set Substitute but it seems that I get mixed results. I'm also having trouble finding documentation detailing how to summarize several smaller subnets into one larger network.

Does anyone have a link to documentation showing how this is supposed to be configured? Or, does anyone have input on the following questions?

- For prefixes, is this an exact match? Or, is this an equal to or greater than mask length match? - I assume that substitute and substitute-status defines and enables/disables the summarizing of addresses matched by the prefix. Is this assumption correct? - What's the purpose of advertise enable/disable?

If there is a alternate/better way to achieve summarization, I'd be interested in that too.

Thanks your for time.

Larry