Ron,
thanks for the help.
I checked the presence of the rsp plugin in the plugins section (in the webbrowser). The rsp plugin is shown, as well as daap and ssc-script. But it’s still not possible to connect from the Pinnacle Soundbridge to Firefly on the NSLU2: the library does not show in the Soundbridge.
I tried turning scan_interval to 0, but this didn’t make any difference.
So perhaps after all it’s a multicast problem of the router?