Rather than using the built-in switch in GNS3
you can use an EtherSwitch module directly within one of your routers.
So here’s what they physically look like
and this would allow you to connect devices to a router
and then provide things such as power over Ethernet in the physical network
so your router with the EtherSwitch module is acting a like a switch
there's information about this on Cisco website
as an example, you could install the EtherSwitch modules in routers such as 3725
and 3745 or something like a 3600 switch.
So there are different EtherSwitch modules available
you could even buy this on eBay
but rather than doing that and paying $170.00 or $245.00 as an example
for an EtherSwitch module or something like $20.00
what we gonna do is we gonna take 1 of the routers and then we're gonna configure it
and in slots, we gonna specify the network module 16ESW.
So this router now has switching capability built-in to it.
I’m gonna do the same thing with router 2
right click select configure select a slot and insert NM-16ESW.