As your topologies become more sophisticated, it is certain that you will want to add VLANs to your configurations. If you are only concerned about carrying VLANs between routers, the Dynamips generic Ethernet switch does a good job. But if you want to begin practicing VLAN configuration on a simulated Cisco switch, then the closest you can get to a real switch is the EtherSwitch router.
The generic Ethernet switch does not require any Cisco image and is managed completely by Dynamips, making its demand on resources far less than a Cisco device. It uses Cisco terminology to describe the port types as access, dot1q, or qinq.