Intermittent connection issue between static IPs

I have a block of five static IPs with two of them active. All firewalls are disabled and each of the two static IPs are associated with a "Online Trusted Static Device" and everything works fine when an external IP address connects. However, connecting from one static IP to the other mostly doesn't work and only intermittently does a connection occur. To illustrate this, if a machine on the network behind the first active IP connects to the second active IP, the connection isn't established most of the time, and, a large delay occurs at times when a connection is established.

For example, from a computer behind the first active IP, here are some observations:

traceroute ${IP2}     # results shown is internal computer IP -> 96.120.*.* (this is a Comcast IP address and not one of the static IPs assigned to my account) -> static block gateway IP address (sometimes this is skipped) ->  second active static IP address

curl http://${IP2}   # there is a service listening on port 80 and serving requests, as verified by connecting to the IP2 from external source, but coming from internal IP1 lan, it results in large delays and nothing or sometimes actually returns a result

How can the connection from IP1 to IP2 be done?

For what it's worth, the network behind IP2 is wired-only and I'm currently bypassing this issue by connecting a computer to both the IP1 network and the IP2 network.