How to open access to the network interface to all machines in the local network?

Question

linux

There are 10 vps-machines purchased from one domestic hoster. vps is connected to the local network. Each machine has 2 static white ip addresses.
There is a php-curl script that sends requests. The script passes the parameter CURL_INTERFACE:xx.xx.xx.xx
where xx.xx.xx.xx is one of the allocated ip addresses of the machine or the interface name.

Question. Is it possible to use the ip of another server on the local network to send a request without raising a proxy server?