You can use iperf that use client and server scenario to test network speed between two Linux based servers. The tool iperf is available in EPEL free repository else you can download from https://iperf.fr/iperf-download.php
The following iperf command will send a buffer size enough to test network speed for 120 seconds
iperf3 -i 5 -t 120 -c <hostname or ip address of server>
On the server side, start iperf with
iperf3 -i 5 -s
iperf server listens on TCP port 5201. Allow port 5201 in server firewall to allow server-client connection. If you want to change server listening port use -p option on command line.
Other alternative tools to iperf is ttcp, nc, and netcat.