An administrator replaces the network card in a web server. After replacing the network card some users can access the server but others cannot. Which of the following is the FIRST thing the administr

The default gateway dictates how a server routes traffic to devices outside its local subnet. If the new network card's IP configuration, specifically the default gateway, is incorrect or missing, the server can only communicate with devices on its local subnet, leading to users on the same subnet having access while users on different subnets cannot.

If the ports on the switch were the issue, either no one would be able to access the server, or connectivity would be intermittent for all users, not selectively based on their network location.

Port security, if triggered, would typically block all traffic from the port or shut it down, rather than allowing some users access while blocking others based on their network location.

An issue with the Ethernet cable would most likely result in no connectivity at all or highly intermittent connectivity for everyone, not selective access based on user network location.