[CentOS] Need help getting two NICs to work on CentOS 7

Hello all

Here is the scenario: We have a mail server VM which currently has two virtual NICs attached to it. One NIC is has an IP on a subnet with a default gateway defined and the other NIC has an IP on a different subnet with a different gateway on a different VLAN defined. Now when I activate both NICs, and run an ifconfig -a, I see that both IP addresses are showing. Now here is the problem. When I ping the VM, the first NIC's IP is not pingable at all, but the second NIC's IP is pingable. How do I configure the networking so that both IPs are pingable and the VM is reachable via both IPs? Please let me know what I may be doing wrong!

Thank you!

Sean