Volume II Lab 14 task 1.5
This one was curious.
I'm not sure of the reason yet but i've isolated 2 aspects that could make the difference.
Switch 3 and 1 have not direcly connection previous this task.
SG solution is already known, my solution was to activate interswitch links between SW1 and SW3, configure both the links of each switch in VLAN 1363 (on both sides!), then activating routing on SW3, configuring the 2 ports on SW1 as protected ports to isolate their traffic.
Finally, to force SW1 to route outside the traffic for the local mac address of R3 i entered on both the routers a static arp entry pointing to the mac address of SW3 vlan 1363 interface to do some sort of manual proxy arp. At end of the story the ping worked fine but the big difference, as opposed to the SG, was that in my way i have not EIGRP neighborship between R1 and R3.
This is not dramatic since there is communication and also R6 form a direct neighborship with them but shouldn't be normal for me that although being in the same subnet, the 2 routers cannot form direct adjacency between them. And probably because they route through an address (SW3 SVI interface) that even though belong to the same subnet, it separates them in some way, because R1 and R3 use that ip for the proxy arp resolution to retrieve the ip of R3 or R1
I don't know if the solution i used could be anyway considered valid but i thought worth to share this since actually i've used a proxy-arp for an address that resides on a common subnet. That was funny