You can run setup and change the IP of interfaces or edit the hosts file (for persistence of the change)...or run ifconfig on the console for a temporary change. No dhcp unless you are setting up bmc/rlm/sp which isn't on the simulator. The 7.x simulators had an exception if I remember during the setup.sh script but I don't know of a way to do dhcp on the 8.x VSIMs. I just set a range of IPs for my VSIMs and hard set them.
Could be the vmnet. If the guest isn't on the same vmnet as the other guest. Or try to ping from the host running workstation/fusion/or player. Check that the vmnet is the same network subnet as the ip you assigned. Probably on vmnet8