Search:

index=foo | dedup 1 host sortby -_time |rex field=host "(?P<device>.*)" | stats count by staticIP device| lookup networks device OUTPUT network | where cidrmatch(network,staticIP)

Lookup:

device, network
Router0, 10.0.0.0/8
Router1, 132.10.0.0/16
Router1, 188.2.0.0/16
Router2, 89.0.0.0/8
Router3, 192.168.0.0/16
Router4, 26.3.0.0/16

Results:

staticIP 	device 	count 	network
26.3.55.0	Router4	1	26.3.0.0/16
192.168.0.0	Router3	1	192.168.0.0/16
192.168.128.0	Router3	1	192.168.0.0/16
89.128.0.0	Router2	1	89.0.0.0/8

There are results missing for Router1, it should show 132.10.0.0 and 188.2.30.0.

If I remove one of the Router 1 entries, I get the following

staticIP 	device 	count 	network
26.3.55.0	Router4	1	26.3.0.0/16
192.168.0.0	Router3	1	192.168.0.0/16
192.168.128.0	Router3	1	192.168.0.0/16
89.128.0.0	Router2	1	89.0.0.0/8
188.2.30.0	Router1	1	188.2.0.0/16

Note the entry for Router1