What networking gotchas have you hit in the past? TCAMs, licensing, other limitations?

I recently implemented a new switch stack from a new vendor and hit an issue with running out of TCAM entries for access control lists / firewall filters. Turns out these specifications aren’t documented anywhere that I can find, and unfortunately I wasn’t aware it was a consideration.

I’m in the middle of doing a NGFW evaluation (Checkpoint, Palo, Fortinet, etc) and I’m wondering what sorts of things might not be so intuitive to include as a part of the evaluation.

Im curious what other people might have run into over the years that others would find helpful, firewalls or otherwise?