Here is a clear overview of the Cisco EHWIC-4ESG module — what it’s used for and its key specifications:
What Cisco EHWIC-4ESG Is Used For
The Cisco EHWIC-4ESG (Enhanced High-Speed WAN Interface Card – 4-port Ethernet Gigabit) is a plug-in switch module designed to expand the capabilities of Cisco Integrated Services Routers (ISR), especially ISR G2 models such as the 1900, 2900, or 3900 series. �
Typical Uses
Add Gigabit Ethernet ports to a router: It gives routers additional four 10/100/1000 Mbps Ethernet ports directly inside the router chassis without needing an external switch. �
Router-Switch.com
Layer-2 switching at wire speed: Ports act like normal switch ports supporting VLANs, spanning tree, QoS, and etc