F5 Fundamental Lab-can't communicate between servers

In VMware player or workstation pro, Host-Only network is just for the purpose as the name reads. You use it to establish communication channel between your Host and Guests. This will be suitable for management interface (if no internet connectivity is needed) and external interface so that your host can access VIPs.

Guest-to-Guest communication does not work with Host-Only networking. If you run native instances of web-servers, then you can use Host-Only networking for internal segment, but if you virtualize them, you can not.

With virtualized web-servers, your internal network needs Guest-to-Guest connectivity (BigIP to servers, and servers to BigIP). Your best choice here is to use "Lan Segment" for the respective network adapter.

My own lab on VMware was built as follows:

NetAdapter 1 (Management). NAT for internet connectivity via mgmt interface (a)
NetAdapter 2 (Client-Side/External). Host-Only with host adapter and DHCP disabled
NetAdapter 3 (Server-Side/Internal). Lan Segment 1
NetAdapter 4 (HA). Lan Segment 2

a) NAT also hides the mgmt interface from other folks in same network. If you build
 your lab on top of a laptop that you occasionally take to a conference or workplace,
 you should never use bridged networking in place of NAT for internet connectivity

With this setup, I could freely pick whether I use VLAN tagging or not. Also the routing can be implemented cleanly as in production-like environments without the requirement to use SNAT. Asymmetric routing issues are avoided by design.

Good luck with the studies and regards,