When you replace the NIC cards in the Nutanix AHV cluster, it is possible that the new NIC card interfaces are recognised as additional interfaces and are numbered after the existing interfaces. So, for example, in the current AHV node you have 4 interfaces - eth0, eth1, eth2 and eth3 and you replace the NIC card and you see additional interfaces - eth0, eth1, eth2, eth3, eth4 and eth5.
Also, if your host was connected earlier on the replaced NIC card, you will lose the host connectivity.
We now have the script in AOS 5.10.10 and AOS 5.15 to get the NIC interfaces re-numbered correctly. If you are running older versions or unable to run the script for any reason, you can use the annual method. Please check the Nutanix portal page here and KB3261 for the exact script and the manual method steps.