Does the Linode Cloud Firewall affect private traffic?

Based on my testing, it seems like it does. When I turn on the Linode Cloud Firewall, then my servers (in same datacenter) can no longer communicate on their private IPs.

But when I try to add rules allowing traffic on private IPs to the Linode Cloud Firewall, I get an error "Must contain only valid IPv4 addresses or networks (both must be in ip/mask format)"

Any ideas?