Hello!
The size of each entry in the DHCP Snooping database is documented in the DHCP Snooping Binding Database section of the "Configuring DHCP" chapter in the IP Addressing Services Configuration Guide, Cisco IOS XE Bengaluru 17.6.x (Catalyst 9300 Switches) document:
"Each entry is 77 bytes, followed by a space, the checksum value, and the EOL symbol."
The same document also indicates that the DHCP Snooping database can have a maximum of 64,000 entries:
"When DHCP snooping is enabled, the switch uses the DHCP snooping binding database to store information about untrusted interfaces. The database can have up to 64,000 bindings."
So with a bit of arithmetic, we can conclude that the DHCP Snooping database will have a maximum size of about 4,928,000 bytes (~5 megabytes). The actual size may be slightly higher due to the static overhead of table headers in the database, which take up a few bytes total.
Since each entry in the database has a relatively static length, the size of the DHCP Snooping database will grow linearly with the number of DHCP clients the switch snoops.
I hope this helps - thank you!
-Christopher
