We have mutiple networks on interfaces for 172.20.0.0/24 172.30.0.0./24 etc.
instead of adding the all the networks individually can I just add 172.16.0.0/12, as this whole range is used across the network.
Hey. Nope, you can’t. OSPF can advertise networks on router’s links only and only thing you can do is summarize them in order to not write them all. But you will advertise only real networks.
@marcocamza If you mean add /12 in OSPF network configuration so that OSPF runs on all matching networks, then yes you can do it.
If you mean to advertise /12 instead /24 then no, unless you run those networks in area, then you can do summarization on ABR.