ciao devi usare il modulo switch come indicato nelle FAQ
Is switching supported in GNS3?
Switching is covered in three important methods. Using a switch that comes with GNS3 in the devices section, herein referred to as a 'basic’' switch. This device is configurable for basic trunks in dot1q as well as access ports. You can assign interfaces as well. It's only intended for functional switching in connecting other devices in the topology.
Using a switching interface inside an existing router. The Cisco 3725 has been tested to support an NM-16ESW module. This module adds 16 Ethernet ports. Configure layer 2 connections like Etherchannel and VLANS. USE a separate virtual machine to run the software image. This option is the most versatile. ALL switching vendors can use their hardware emulator (like VMware, Virtualbox, qemu), load up their software, then use gns3 to connect their ports together.
Devi quindi configurare un router con il modulo NM-16ESW che permette di usare circa 90% delle funzioni di uno switch adattando alcuni comandi.
Le funzioni generiche degli switch sono supportate ma per le funzioni specifiche del 2960XR no ( ridondanza alimentazione, FlexStack, IP Lite Cisco IOS software with dynamic routing and Layer 3 features). Per il routing chiaramente il modulo è inserito in uno switch quindi il routing funziona ma dovrai adattare le configurazioni.