in addition to Sankar´s post, you might want to have a look at the document below, which explains how to configure the HWIC-4ESW. Basically, the module gives you 4 switchports, similar (or actually equal to) a small built-in switch. In order for the ports to function in different (V)Lans, you need to configure inter-Vlan routing on your 2801. Let´s say you have 3 subnets, each of which needs its own default gateway. Your router configuration would look like this:
ip address 192.168.1.1 255.255.255.0
ip address 192.168.2.1 255.255.255.0
--> These are the two built-in FastEthernet ports. For the third subnet, 192.168.3.0/24, you will need to configure a Vlan interface:
ip address 192.168.3.1 255.255.255.0
Most likely, you will have a switch connected to one of the FastEthernet ports of the HWIC-4ESW on the router, this needs to be configured as a trunk:
switchport mode trunk
switchport trunk native vlan 3
The port on the switch connected to that interface needs to be configured as a trunk as well.
Cisco HWIC-4ESW and HWIC-D-9ESW EtherSwitch Interface Cards
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...