My company is setting up a firewall and we've got a number of Oracle databases. One person mentioned that Cisco Pix firewalls are Oracle certified. I did some research and it seems that these firewalls have a special way of handling the SQL*Net protocol. From Cisco, referring to SQL*Net:
The protocol consists of different packet types that PIX Firewall handles to make the data stream appear consistent to the Oracle applications on either side of the firewall.

Have people run into problems using firewalls other than Cisco? I can't imagine that Oracle only works w/ Cisco firewalls. We're considering a Juniper NetScreen-5GT firewall and I just want to make sure we're not going to run into any problems.