The IP's look correct for this setup. What packet filter rules or features have you configured on the astaro?
A basic packet filter rule to allow traffic from the internal network to the internet would be:
Source: Internal (network) [192.168.0.0/24] Service: Any Destination: Any Action: Allow
In this scenario you shouldn't need any NAT masq rules, but the linksys may not have a route for the 192.168.0.0 network so you may need to create one or add a route on the linksys.