This scheme has many point of failures, there is no high availability.
Working with this scheme and its components we have: If Router 1 is down everything goes down (at left side), Now you if Hub1 is a switch, you can use 2 interfaces (trunk mode) and connect them to Hub2 (switch2) and to Hub3 (switch3) respectively and create the Host1's vlan on each switch and create finally the gateway for the Host1 on the Router 2, like it is created for Host 2 and 3.
Basically Hub 1 will skip the Router 1, now router 2 will be the gateway for the host 1.
Other option is connect the Host 1 to the router 2 or router 3 directly to an ethernet port (using crossover cable) and create the gateway on one of these routers, if it will be connected to router 3 remember configure the interface with ip nat inside and include the subnet into the ACL to get internet access.
*Remember verify the routing for the host 1.
Hope it is useful
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